12. Sponsoring Agency Name and Address

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

6. AUTHOR(S)
M. D. Williams
8. PERFORMING ORGANIZATION REPORT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
NASA Langley Research Center Hamptቤተ መጻሕፍቲ ባይዱn, VA 23665-5225
A02
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Standard Form 298(Rev. 2-89)
Prescribed by ANSI Std. Z39-18 298-102 NASA-Langley, 1992
A technology for transmitting high power by laser beam over large distances using a quasi-coherent array of lasers is described. This technology achieves quasi-coherency by turning OFF selected laser elements, rather than trying to correct their phase as present technologies do. Such an array puts less power into a speci ed area in the far eld than a fully coherent array but gains two major advantages: (1) laser array elements are greatly simpli ed and less expensive and (2) array lifetime can be lengthened. The degree of coherency can be chosen. The greater the coherency, the greater is the lifetime of the array (for a speci ed power transmission requirement). More laser elements remain inactive. Also, by making array element selection a dynamic process, the technology can actively correct any phase changes induced in the array. The technology is analyzed, results of a computer experiment are presented, and a laboratory experiment for further development of the technology is proposed. For many years, NASA has studied the transmission of power by laser beam (refs. 1 and 2), with potential applications identi ed both in space and on Earth. Such applications require high power (up to megawatts) di raction limited laser systems. One method to obtain such systems is to assemble arrays of less powerful lasers which can be scaled to the laser power required. Arrays also lend themselves to building the large apertures required for transmission over large distances. The larger the transmission aperture is, the smaller the received laser spot size for a given range. Arrays have usually been described in terms of their ultimate power transmission capability (i.e., the maximum power that a coherent array could transmit into a speci ed area in the far eld). Coherent arrays transmit optical amplitudes that are in phase in space and time. Although coherent arrays are feasible, they are very di cult to obtain in practice. They require complex and expensive electro-optical components that are still challenged by the dynamics of a real system (i.e., heat distribution, alignment, mechanical stress). Thus, the questions arise: \Is the power transmission loss due to incomplete coherence worth the cost of obtaining complete coherence?" and \Are there other advantages of a partially coherent array?" These questions have led to an idea labeled \dynamic selection of emitting laser array elements." This idea represents a new approach to obtaining concentrated laser power in the far eld. In this approach, laser array elements are not \forced" to be perfect (coherent) but are simply turned OFF

CONTRIBUTIONS

DOT/FAA/AR-01/31 Office of Aviation Research Washington, D.C. 20591Calculating Polymer Flammability From Molar Group ContributionsSeptember 2001Final ReportThis document is available to the U.S. publicthrough the National Technical InformationService (NTIS), Springfield, Virginia 22161.U.S. Department of TransportationFederal Aviation AdministrationNOTICEThis document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The United States Government assumes no liability for the contents or use thereof. The United States Government does not endorse products or manufacturers. Trade or manufacturer's names appear herein solely because they are considered essential to the objective of this report. This document does not constitute FAA certification policy. Consult your local FAA aircraft certification office as to its use.This report is available at the Federal Aviation Administration William J. Hughes Technical Center’s Full-Text Technical Reports page: in Adobe Acrobat portable document form (PDF).Technical Report Documentation Page1. Report No.DOT/FAA/AR-01/312. Government Accession No.3. Recipient's Catalog No.5. Report DateSeptember 20014. Title and Subtitle CALCULATING POLYMER FLAMMABILITY FROM MOLAR GROUPCONTRIBUTIONS6. Performing Organization Code7. Author(s)Richard Walters* and Richard E. Lyon**8. Performing Organization Report No.9. Performing Organization Name and Address *Galaxy Scientific Corporation **Federal Aviation Administration English Creek Avenue, Building C William J. Hughes Technical Center Egg Harbor Township, NJ 08234 Airport and Aircraft Safety10. Work Unit No. (TRAIS)Research and Development Fire Safety Section Atlantic City International Airport New Jersey 0840511. Contract or Grant No.12. Sponsoring Agency Name and Address U.S. Department of Transportation Federal Aviation Administration13. Type of Report and Period CoveredFinal Report Office of Aviation Research Washington, DC 2059114. Sponsoring Agency Code AIR-12015. Supplementary Notes 16. AbstractSpecific heat release rate is the molecular-level fire response of a burning polymer. The Federal Aviation Administration (FAA)obtains the specific heat release rate of milligram samples by analyzing the oxygen consumed by complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat release rate (W/g) by the rate of temperature rise (K/s) gives a material fire parameter with the units (J/g-K) and significance of a heat (release) capacity. The heat release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical composition have been tested to date, providing over 40different empirical molar group contributions to the heat release capacity. Measured and calculated heat release capacities for 80polymers agree to within ±15%, suggesting a new capability for predicting flammability from polymer chemical structure.17. Key Words Thermochemistry, Polymer flammability, Group contributions, Heat release, Fire, Combustion, Pyrolysis,Kinetics18. Distribution StatementThis document is available to the public through the National Technical Information Service (NTIS), Springfield, Virginia 22161.19. Security Classif. (of this report) Unclassified20. Security Classif. (of this page)Unclassified 21. No. of Pages 3222. PriceACKNOWLEDGEMENTSThe authors are indebted to Dr. Stanislav I. Stoliarov of the University of Massachusetts (Amherst) for performing the optimization calculations for the molar group contributions to the heat release capacity. Certain commercial equipment, instruments, materials, or companies are identified in this report in order to adequately specify the experimental procedure. This in no way implies endorsement or recommendation by the Federal Aviation Administration.TABLE OF CONTENTSPage EXECUTIVE SUMMARY vii INTRODUCTION1 THEORY1 EXPERIMENTAL3 Materials3 Methods3 RESULTS4 Calculation of Heat Release Capacity19 Heat Release Capacity and Fire Hazard20 Heat Release Capacity and Flammability21 CONCLUSION23 REFERENCES23LIST OF FIGURESFigure Page 1Schematic Diagram of the Pyrolysis-Combustion Flow Calorimeter3 2Specific Heat Release Rate Data for Several Polymers Measured in the Microscale Calorimeter5 3Calculated Versus Measured Heat Release Capacities for 80 Pure Polymers19 4Average Flaming Heat Release Rate Versus Heat Release Capacity for Several Polymers21 5UL-94 Ratings Versus Measured Heat Release Capacities of Pure Polymers22 6Plot of Limiting Oxygen Index Versus Measured Heat Release Capacity22LIST OF TABLESTable Page1.Polymer Structure and Values Derived From Pyrolysis-Combustion FlowCalorimetry62.Structural Groups and Their Molar Contribution to the Heat Release Capacity183. Group Contributions Used in the Calculation of the Heat Release Capacity ofBisphenol-A Epoxy20EXECUTIVE SUMMARYSpecific heat release rate is the molecular-level fire response of a burning polymer. The Federal Aviation Administration (FAA) obtains the specific heat release rate of milligram samples by analyzing the oxygen consumed by complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat release rate (W/g) by the rate of temperature rise (K/s) gives a material fire parameter with the units (J/g-K) and significance of a heat (release) capacity. The heat release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical composition have been tested to date, providing over 40 different empirical molar group contributions to the heat release capacity. Measured and calculated heat release capacities for over 80 polymers agree to within ±15%, suggesting a new capability for predicting flammability from polymer chemical structure.INTRODUCTIONThe additivity of molar group contributions to the physical and chemical properties of polymers is the basis of an empirical methodology for relating chemical structure to polymer properties [1-3]. The early work in this area [4] focused on calculating heats of combustion from the individual atoms comprising small molecules. However, performing calculations for large (polymer) molecules based on the interactions of the individual atoms can prove to be very difficult [2]. A simpler approach to correlating polymer chemical structure with properties is to group the atomic contributions into characteristic structural elements (e.g., –CH3), determine the value of the group contribution to the property of interest parametrically, and add these group contributions according to their mole fraction in the polymer repeat unit. This method has been used to relate the chemical structure of polymers to their thermal, chemical, optical, and mechanical properties with excellent results [1-3]. Of particular interest in the present context is the ability to predict thermal stability parameters (pyrolysis activation energy, thermal decomposition temperature, char/fuel fraction) from additivity of polymer molar group contributions [1].Prerequisite to any structure-property correlation is the ability to identify and reproducibly measure the intrinsic property of interest. In the area of polymer flammability, no single material property has correlated with fire performance, nor does any test measure fire performance unambiguously because burning rate, ignitability, flammability, and heat release rate are not intrinsic properties. Rather, they are extrinsic quantities resulting from the reaction of a macroscopic polymer sample to a severe thermal exposure. Because the sample size in a flammability or fire test is orders of magnitude larger than the chemical process zone [5-7], heat-and mass-transfer dominate the fire response. Thus, an intrinsic material property for use by scientists in designing fire-resistant polymers is not obtainable from standard fire or flammability tests.Recently, a material fire parameter [5-7] (the heat release capacity) has been identified that appears to be a good predictor of the fire response and flammability of polymers. A quantitative laboratory pyrolysis-combustion method for directly measuring the heat release capacity has been reported [8-10]. This report presents experimental data which suggests that heat release capacity is the material property that correlates polymer structure and fire behavior.THEORYThe solid-state thermochemistry of flaming combustion [5-7] reveals a material fire parameter that has the units (J/g-K) and significance of a heat (release) capacity,η=(1)cpThe heat release capacity is a combination of thermal stability and combustion properties, each of which is known to be calculable from additive molar group contributions [1]. The component material properties are the heat of complete combustion of the pyrolysis gases, h c o(J/g); the weight fraction of solid residue after pyrolysis or burning, µ(g/g); the global activation energyfor the single-step mass loss process, pyrolysis, E a (J/mole); and the temperature at the peak mass loss rate, T p (K), in a linear heating program at constant rate, β (K/s). The constants in equation 1 are the natural number e and the gas constant R. Equation 1 shows the heat release capacity to be a particular function of thermal stability and combustion properties, each of which is known to be calculable from additive molar group contributions [1]. Consequently, ηc itself is a material property and should be calculable from the same (or similar) molar groups as the component properties as long as there are no interactions between the chemical structural units. From this assumption of group additivity and the postulate that for a polymer repeat unit of molar mass M, there is a molar heat release capacity ψ with units of J/mole-K whose functional form is equation 1 but with the thermal stability and combustion properties written as molar quantities, H, V, E, and Y/M in place of h c o, (1-µ), E a and T p, respectively. If each chemical group i in the polymer adds to the component molar properties according to its mole fraction n i in the repeat unitΨ=H V EeR(Y/M)2=(2)with H i, V i, E i, Y i, and M i the molar heat of combustion, mole fraction of fuel, molar activation energy, molar thermal decomposition function [1], and molar mass of component i, respectively. Expanding the summations in equation 2 and retaining only the noninteracting terms for which i = j = k … (i.e., neglecting terms containing products and quotients with mixed indices),Ψ=ni =niΨi ΣiΣi(3)Equation 3 shows that there is a molar group contribution to the heat release capacity ψi that adds according to its mole fraction in the repeat unit of the polymer. If N i and M i are the number of moles and molar mass, respectively, of group i in the polymer having repeat unit molar mass Mn i =NiNiΣiand M=n i M iΣi=NiNiΣiMiΣithen the heat release capacity on a mass basis isηc =ΨM=niΨiΣiniMiΣi=NiΨiΣiNiMiΣi(4)Equations 2 through 4 provide the physical basis for an additive heat release capacity function, but the values of the molar contributions of chemical groups must be derived empirically (i.e., experimentally). To this end, the heat release capacities of more than 200 polymers with known chemical structure have been measured using the measurement technique described below and these experimental values have been used to generate over 40 group contributions[11 and 12].EXPERIMENTALMATERIALS .Polymer samples were unfilled, natural, or virgin-grade resins obtained from Aldrich Chemical Company, Scientific Polymer Products, or directly from manufacturers. Oxygen and nitrogen gases used for calibration and testing were dry, >99.99% purity grades obtained from Matheson Gas Products.METHODS .A pyrolysis-combustion flow calorimeter (PCFC) [8-10] was used for all experiments (see figure 1).FIGURE 1. SCHEMATIC DIAGRAM OF THE PYROLYSIS-COMBUSTIONFLOW CALORIMETERIn this device, a pyrolysis probe (Pyroprobe 2000, CDS Analytical) is used to thermally decompose milligram-sized samples in flowing nitrogen at a controlled heating rate. The samples are heated at a constant rate (typically 4.3 K/s) from a starting temperature which is several degrees below the onset degradation temperature of the polymer to a maximum temperature of 1200 K (930°C). The 930°C final temperature ensures complete thermal degradation of organic polymers so that the total capacity for heat release is measured during the test and equation 1 applies. Flowing nitrogen sweeps the volatile decomposition products from the constant temperature (heated) pyrolysis chamber, and oxygen is added to obtain a nominal composition of 4:1, N 2:O 2, prior to entering a 900°C furnace for 60 seconds to effect complete nonflaming combustion. The combustion products (carbon dioxide, water, and possibly acid gases) are then removed from the gas stream using Ascarite™ and Drierite™ scrubbers. Themass flow rate and oxygen consumption of the scrubbed combustion stream are measured using a mass flowmeter and zirconia oxygen analyzer (Panametrics Model 350), respectively.The specific heat release rate Q c in the pyrolysis-combustion flow calorimeter is determined from oxygen consumption measurements by assuming that 13.1 kJ of heat is released per gram of diatomic oxygen consumed by combustion [13-16]. Since Q c is equal to the fractional mass loss rate multiplied by the heat of complete combustion of the pyrolysis productsQ c (t )=E m o ∆O 2(t )=–h c ,v °(t )m o d m (t )d t(5)where E = 13.1 ±0.6 kJ/g-O 2, ∆O 2 is the instantaneous mass consumption rate of oxygen, m o isthe initial sample mass, h c ,v 0is the instantaneous heat of complete combustion of the volatile pyrolysis products, and dm/dt is the instantaneous mass loss (fuel generation) rate of the sample during the test. The advantage of synchronized oxygen consumption calorimetry to determine the specific heat release rate is the ease and speed of the method compared to simultaneous measurement of the mass loss rate of the solid and the heat of combustion of the pyrolysis gases [17]. At the temperature of maximum mass loss rate T p , the specific heat release rate has an analytic form [18, 5-7]Q cmax =E m o ∆O 2max =–h c ,v °(t )m o d m (t )d tmax=hc°p(6)The rate-independent heat release capacity is obtained from equation 6 by dividing the maximum specific heat release rate by the constant sample heating rate, β (K/s)ηc ≡Q c max β=E βm o ∆O 2max =p (7)The quantities measured in the test are the specific heat release rate Q c (W/g); the heat releasecapacity ηc (J/g-K) calculated from the peak specific heat release rate and the linear heating rateof the sample; the total heat released by complete combustion of the pyrolysis gases h c 0(J/g); and the residual mass fraction µ (g/g) after the test.RESULTSPyrolysis-combustion flow calorimeter data for the specific heat release rate of polyethylene (PE), polypropylene (PP), polystyrene (PS), an acrylonitrile-butadiene-styrene terpolymer (ABS), polymethymethacrylate (PMMA), polyethyleneterephthalate (PET), polyetheretherketone (PEEK), and polybenzimidazole (PBI) are shown in figure 2, horizontally shifted for clarity.Dividing the maximum specific heat release rate (W/g) measured during the test (peak height in figure 2) by the constant sample heating rate (β = 4.3 K/s in these tests) gives the heat release capacity of the polymer in units of J/g-K for materials which thermally decompose in a singlestep. Materials exhibiting multiple heat release peaks are beyond the scope of this report andwill be addressed in the future.-400-200020040060080010001200140016001800050100150200250300H e a t R e l e a s e R a t e (J /g -K )Time (seconds)FIGURE 2. SPECIFIC HEAT RELEASE RATE DATA FOR SEVERAL POLYMERSMEASURED IN THE MICROSCALE CALORIMETER(Horizontally shifted for clarity)Measured heat release capacities for more than 100 polymers with known chemical structure are shown in table 1. This data has been used to generate the group contributions shown in table 2.The molar group contributions were obtained by treating the Ψi as adjustable parameters in the linear system of equations (equation 4) for polymers with known chemical structures and measured ηc . The optimization calculation continued until the sum of the squares of the relative error between the measured ηc and the value calculated from group contributions was a minimum. The calculation converged rapidly to the unique Ψi listed in table 2 which were independent of initial estimates.T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R YT A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )T A B L E 1. P O L Y M E R S T R U C T U R E A N D V A L U E S D E R I V E D F R O M P Y R O L Y S I S -C O M B U S T I O N F L O W C A L O R I M E T R Y (C o n t i n u e d )TABLE 2. STRUCTURAL GROUPS AND THEIR MOLAR CONTRIBUTION TO THE HEAT RELEASE CAPACITY (Molar group contributions derived from asingle polymer are marked with an asterisk (*).)Figure 3 is a plot of calculated versus measured heat release capacities for over 80 polymers for which optimized Ψi were determined. The correlation coefficient between measured and predicted heat release capacities is r = 0.96 and the average relative error is ±15%.0300600900120015001800C a l c u l a t e d H R C a p a c i t y (J /g -K )Measured HR Capacity (J/g-K)FIGURE 3. CALCULATED VERSUS MEASURED HEAT RELEASE CAPACITIESFOR 80 PURE POLYMERS CALCULATION OF HEAT RELEASE CAPACITY.The following example illustrates the calculation of heat release capacity from molar group contributions for a diglycidylether of bisphenol-A (BPA epoxy) cured by anionic ring opening polymerization. This polymer has the repeat unit chemical structureCH 2CH CH 2OC CH 3CH 3O O CH 2CHCH 2O**The polymer repeat unit is comprised of six basic chemical groups, and the heat release capacity is calculated from the associated N i , M i , and Ψi for these groups, which are listed in table 3.TABLE 3. GROUP CONTRIBUTIONS USED IN THE CALCULATION OF THE HEATRELEASE CAPACITY OF BISPHENOL-A EPOXYThe molar heat release capacity is obtained by summing the group contributions according to their mole fraction in the repeat unit, then dividing by the molar mass of the repeat unit to give the heat release capacity on a mass basis in units of J/g-K.ηc=ΨM=niΨiΣiniMiΣi=NiΨiΣiNiMiΣi=204.5kJ/mole–K340g/mole=601J g–KThe predicted value of 601 J/g-K compares favorably with the measured value of 657 J/g-K for this polymer.HEAT RELEASE CAPACITY AND FIRE HAZARD.The primary indicator of the fire hazard of a material is the heat release rate in forced flaming combustion [19]. Figure 4 is a plot of the average flaming heat release rate (HRR) of 10- by 10-by 0.64-cm (≈ 80-g) samples of pure polymer measured in a fire calorimeter at an external heat flux ˙qext= 50 kW/m2 according to standard methods [20-22] versus the measured heat release capacity. Proportionality is observed between the flaming heat release rate of kilogram-sized samples and the heat release capacity of milligram-sized samples of the same polymer with slope 1.0 (kg/s)/m2/K, in general agreement with predictions for steady burning [5-7]. Consequently,ηc is a reasonable predictor of fire hazard using the physically based empirical correlation in figure 4.200400600800100012001400A v e r a g e F l a m i n g H R R (k W /m 2)Heat Release Capacity (J/g-K)250150050075010001250FIGURE 4. AVERAGE FLAMING HEAT RELEASE RATE VERSUS HEATRELEASE CAPACITY FOR SEVERAL POLYMERSHEAT RELEASE CAPACITY AND FLAMMABILITY .Flammability is taken here to mean the tendency of a thin sample of material ignited by a Bunsen burner to continue burning in the absence of a radiant heat source after removal of the burner.Self-extinguishing behavior in these tests implies a certain resistance to flame propagation, and standard methods have been developed to measure this characteristic. These flame tests are widely used to rank the burning propensity of combustible solids but they do not yield any material property information. Two common flammability test methods are the Underwriters Laboratories UL 94 test for upward vertical (V) and horizontal burning (HB) [23] and the critical oxygen concentration for flame extinguishment or limiting oxygen index (L.O.I.) in downward burning [24].In the absence of an external heat flux from a radiant heater or fire, the flame heat flux at the sample tip must provide all of the thermal energy to degrade the solid polymer surface to gaseous fuel. If the flame heat flux is constant (UL 94 test) or increases in a known way with oxygen concentration (L.O.I.), the criterion for self-extinguishing behavior in these tests can be formulated in terms of a critical heat release capacity by assuming that a minimum heat release rate (typically 100 kW/m 2) is needed to sustain flaming combustion. Such an analysis for the UL 94 test [6] indicates that polymers with ηc ≤ 300 J/g-K do not release heat at a high enough rate after removal of Bunsen burner to overcome heat losses by the sample and thus the flame cannot propagate, they self-extinguish. Thus, for pure polymers with ηc ≤ 300 J/g-K, self-extinguishing behavior (UL 94 V rating) is expected. Figure 5 contains UL 94 data [25] which shows that a transition from burning (HB) to self-extinguishing behavior (V-0) occurs in the vicinity of ηc =300 J/g-K.20040060080010001200U L -94 R a t i n gHeat Release Capacity (J/g-K)V-0V-1V-2HBFIGURE 5. UL-94 RATINGS VERSUS MEASURED HEAT RELEASECAPACITIES OF PURE POLYMERSThe criterion for self-extinguishing behavior in the L.O.I. test must take into account the fact that an increase in the oxygen concentration of the flowing gas stream in the test chamber increases the temperature (radiant heat flux) of the sample diffusion flame and, therefore, the amount of thermal energy incident on the polymer. Since the heat release rate of the sample increases with the flame heat flux, which in turn increases with oxygen concentration, an inverse relationship between ηc and the limiting oxygen concentration is expected and observed, as shown in the L.O.I. data [1, 26, and 27] plotted versus ηcin figure 6.101520253035404550O x y g e n I n d e xHeat Release Capacity (J/g-K)FIGURE 6. PLOT OF LIMITING OXYGEN INDEX VERSUS MEASUREDHEAT RELEASE CAPACITYL i m i t i n g O x y g e n I n d e xAs shown in figures 5 and 6, self-extinguishing behavior in the UL 94 vertical test occurs at a lower heat release capacity (ηc= 300 ±100 J/g-K) than in the L.O.I. test (ηc = 550 ±100 J/g-K) at ambient conditions (298 K, 20% O2). The reason for this is that the L.O.I. test is a downward burning test so there is no buoyancy-driven convective preheating of the polymer by the surface flame as occurs in the UL 94 upward burning test. Since less thermal energy is deposited in the L.O.I. sample from the surface flame at ambient conditions than is deposited in the UL 94 specimen after removal of the ignition sources, the heat release rate is lower in the L.O.I. test and self-extinguishing behavior should (and does) occur at a higher heat release capacity.CONCLUSIONThe heat release capacity is a physically based material property that is a good predictor of the fire behavior and flammability of pure polymers. The heat release capacity is simply calculated for pure polymers from their chemical structure using additive molar group contributions which have been determined empirically with a high level of confidence (±15%). The proposed methodology for predicting the fire behavior and flammability of polymers from their chemical structure allows for the molecular-level design of ultra-fire-resistant polymers without the expense of synthesizing and testing new materials.REFERENCES1. D.W. Van Krevelen, Properties of Polymers, 3rd edition, Elsevier, Amsterdam, 1990.2.Jozef Bicerano, Prediction of Polymer Properties, 2nd edition, Marcel Dekker, Inc., NewYork, NY, 1996.3.M.M. Coleman, J.F. Graf, and P.C. Painter, Specific Interactions and the Miscibility ofPolymer Blends, Technomic Publishing Co., Inc., Lancaster, PA, 1991.4.S.W. Bensen, Thermochemical Kinetics, Methods for the Estimation of ThermochemicalData and Rate Parameters, John Wiley, New York, NY, 1968.5.R.E. Lyon, “Solid-State Thermochemistry of Flaming Combustion,” in Fire Retardancyof Polymeric Materials, C.A. Wilkie and A.F Grand, eds., Marcel Dekker, Inc., NY, 2000.6.R.E. Lyon, “Heat Release Capacity,” Proceedings of the 7th International Conference onFire and Materials, San Francisco, CA, 2001, pp. 285-300.7.R.E. Lyon, “Heat Release Kinetics,” Fire and Materials, 24, pp.179-186, 2000.8.R.N. Walters and R.E. Lyon, “A Microscale Combustion Calorimeter for DeterminingFlammability Parameters of Materials,” Proceedings 42nd International SAMPE Symposium and Exhibition, 42(2), pp. 1335-1344, 1997.9.R. N. Walters and R.E. Lyon, “A Microscale Combustion Calorimeter for DeterminingFlammability Parameters of Materials,” NISTIR 5904, K. Beall, ed., pp. 89-90, 1996.。

美国与欧洲的主动式交通管理经验 Active Traffic Management fhwahop10031

ForewordNoticeThis document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names may appear in this report only because they are considered essential to the objective of the document.Quality Assurance StatementThe Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.Technical Report Documentation Page 1. Report No.FHWA-HOP-10-0312. Government Accession No.3. Recipient's Catalog No.4. Title and SubtitleSynthesis of Active Traffic ManagementExperiences in Europeand the United States 5. Report DateMay2010 6. Performing Organization Code7. Author(s)Chuck Fuhs (Parsons Brinckerhoff)8. Performing Organization Report No.9. Performing Organization Name and AddressParsonsBrinckerhoff1 Penn PlazaNew York, NY 10119-0002(performed as a subconsultant to Cambridge Systematics)10. Work Unit No. (TRAIS)11. Contract or Grant No.DTFH61-06-D-0000412. Sponsoring Agency Name and AddressU.S. Department of TransportationFederal Highway AdministrationOffice of Operations (HOP)1200 New Jersey Avenue, SEWashington, DC 20590 13. Type of Report and Period Covered FinalReport14. Sponsoring Agency CodeHOP15. Supplementary NotesFHWA COTM - Jessie Yung.16. AbstractThis synthesis report describes both US and European techniques in Active Traffic Management (ATM). The primary focus of this synthesis is on European experience, which in some cases dates back a number of years. This report provides a compilation of lessons learned, experiences, operational results, and benefits associated with active traffic management applications. The applications included for discussion are primarily those that include variable speed management (also called speed harmonization or lane control in Europe), shoulder or line management, junction control, and directional routing. The report concludes with a discussion of the potential benefits and challenges of a system-wide application of techniques to actively manage traffic and a listing of initial implementations of European strategies in the US.17. Key WordActive Traffic Management, High Occupancy Toll, High Occupancy Vehicle, Lane Control, managed lanes, speed harmonization, variable speed limit, congestion management, pricing, operations 18. Distribution Statement No Restrictions.19. Security Classif. (of this report)unclassified 20. Security Classif. (of this page)unclassified21. No. of Pages3522. PriceNAForm DOT F 1700.7 (8-72)Reproduction of completed page authorizedTable of Contents1.0 Introduction (1)1.1 Report Purpose (1)1.2 2006 Scan Tour Summary (1)2.0 What Is Active Traffic Management; Why and When Is it Used? (3)2.1 European Traffic Management Strategies (3)2.2 US-based Traffic Management Strategies (4)3.0 US Techniques (5)3.1 Ramp Metering (5)3.2 Managed Lanes (6)3.3 Speed Harmonization (7)3.4 Hard Shoulder Running (12)3.5 Junction Control (15)3.6 Dynamic Re-routing (16)3.7 Traveler Information (18)3.8 Summary (18)4.0 System Level Applications (19)4.1 Overall Roadway Management (19)4.2 Spot Roadway Management Strategies (20)4.3 Incremental Implementation (21)4.4 Adaptation to Existing US ITS and Traffic Operations Investments (22)5.0 Initial US-Based Implementation of European Traffic ManagementStrategies (26)5.1 Under Study (26)5.2 Implementation (26)6.0 References (27)List of FiguresFigure 1. Speed Harmonization Signing in the Netherlands (7)Figure 2. Dynamic Speed Limits in Randstad Area (8)Figure 3. Queue Warning—Side-Mount Congestion Icons (11)Figure 4. Hard Shoulder Running When Active and Inactive (13)Figure 5. Emergency Pull-Outs Associated with Hard Shoulder Running (13)Figure 6. Speed-Volume Relationship of Temporary Shoulder Use (14)Figure 7. Junction Control at an Exit with Hard Shoulder Running (15)Figure 8. Junction Control On-Ramp Schematic (16)Figure 9. Dynamic Route Information in The Netherlands (17)Figure 10. Relationships Between ATM Strategies (19)List of Abbreviations and AcronymsATM Active Traffic ManagementCCTV Closed Circuit TelevisionDMS DynamicMessageSignFHWA Federal Highway AdministrationGP GeneralPurposeHOT HighOccupancyTollHOV HighOccupancyVehicleITS Intelligent Transportation SystemLCD LaneControlDisplayLED Light Emitting DiodeMUTCD Manual on Uniform Traffic Control DevicesNTCIP NationalTransportationCommunications for ITS Protocol O&M Operations and MaintenancePM PreventiveMaintenancePS&E Plans, Specifications and EstimateSOP StandardOperating ProcedureSOV Single-OccupantVehicleTDM TMC Travel Demand Management Traffic Management CenterTMS Transportation Management System UPS Uninterruptible Power SupplyUS UnitedStatesVMS VariableMessageSign VSL Variable Speed Limit1.0 Introduction1.1 Report PurposeThis synthesis report describes both US and European techniques in Active Traffic Management (ATM).The primary focus of this synthesis is on European experience, which in some cases dates back a number of years. This report provides a compilation of lessons learned, experiences, operational results, and benefits associated with active traffic management applications. The applications included for discussion are primarily those that include variable speed management (also called speed harmonization or lane control in Europe), shoulder or line management, junction control, and directional routing. The report concludes with a discussion of the potential benefits and challenges of a system-wide application of techniques to actively manage traffic and a listing of initial implementations of European strategies in the US.1.2 2006 Scan Tour SummaryIn June 2006, a group of eleven US transportation professionals representing planning, design, and operations visited five European nations to study how they were addressing freeway congestion using dynamic or actively managed traffic management techniques. The trip was sponsored by the International Technology Scanning Program, a partnership of AASHTO, FHWA, and the National Cooperative Highway Research Program of TRB. The trip purpose was to examine congestion management programs, policies, and experiences from the perspectives of national, state, and local transportation agencies.The scan team found that through the deployment of these specific traffic management techniques, agencies in Denmark, England, Germany, and The Netherlands exercise increased control over their roadway facilities and are able to better optimize their infrastructure investment to meet customer needs. Depending on the location and the combination of strategies deployed, specific benefits as a result of this congestion management approach include: •An increase in average throughput for congested periods of 3 to 7 percent;•An increase in overall capacity of 3 to 22 percent;• A decrease in primary incidents of 3 to 30 percent;• A decrease in secondary incidents of 40 to 50 percent;•An overall harmonization of speeds during congested periods;•Decreased headways and more uniform driver behavior;•An increase in trip reliability; and•The ability to delay the onset of freeway breakdown.Nine key recommendations were identified by the scan team that would be applicable to congestion management in the United States. The following are the scan team’s primary recommendations (Mirshahi, et al., 2007):1.Promote active management to optimize existing infrastructure during recurrent and non-recurrent congestion.2.Emphasize customer orientation and focus on trip reliability.3.Integrate active management into infrastructure planning and programming processes.4.Make operations a priority in planning, programming, and funding processes.5.Develop tools to support active management investment decisions.6.Consider public-private partnerships and other innovative financing and deliverystrategies.7.Provide consistent messages to roadway users.8.Consider pricing as only one component of a total management package.9.Include (ATM consideration) as part of the overall management of congested facilities.2.0 What Is Active Traffic Management--Why andWhen is it Used?Active Traffic Management is generally regarded as an approach for dynamically managing and controlling traffic demand and available capacity of transportation facilities, based on prevailing traffic conditions, using one or a combination of real-time and predictive operational strategies. When implemented together with traditional traffic demand management strategies, these operational strategies can help to maximize the effectiveness and efficiency of a roadway and result in improved safety, trip reliability and throughput. A truly active management philosophy dictates that the full range of available operational strategies be considered; including the various ways these strategies can be integrated together and among existing infrastructure, to actively manage the transportation system to achieve system performance goals. This includes traditional traffic management and ITS technologies commonly applied in the US, as well as new technologies and non-traditional traffic management technologies more commonly applied in other parts of the world.Active management techniques are utilized throughout the world, but the focus of this synthesis is on those strategies utilized in Europe and the US. While the European and US strategies are different, in many cases they are complementary and may be combined to provide greater benefits than when implemented separately. The following sections describe strategies that are used in Europe and the US to enhance and support the management of roadway facilities either in an individual or combined manner to maximize efficiency and effectiveness of a single roadway facility or a larger roadway network.2.1 European Traffic Management StrategiesThe following list provides a high-level description of strategies currently being deployed in Europe to actively manage traffic:•Speed Harmonization/Lane Control: utilizing regularly spaced, over lane speed and lane control signs to dynamically and automatically reducing speed limits in areas ofcongestion, construction work zones, accidents, or special events to maintain traffic flow and reduce the risk of collisions due to speed differentials at the end of the queue andthroughout the congested area.•Queue Warning: utilizing either side mount or over lane signs to warn motorists of downstream queues and direct through-traffic to alternate lanes – effectively utilizingavailable roadway capacity and reducing the likelihood of collisions related to queuing.•Hard Shoulder Running: using the roadway shoulder (inside or outside) as a travel lane during congested periods to alleviate recurrent (bottleneck) congestion for all or a subset of users such as transit buses. Hard shoulder running can also be used to manage trafficand congestion immediately after an incident.•Junction Control: using lane use control, variable traffic signs, and dynamic pavement markings to direct traffic to specific lanes (mainline or ramp) within an interchange area based on varying traffic demand, to effectively utilize available roadway capacity toreduce congestion•Dynamic Re-routing: changing major destination signing to account for downstream traffic conditions within a roadway network or system.•Traveler Information: providing estimated travel time information and other roadway and system conditions reports allowing travelers to make better pre-trip and in-routedecisions.2.2 US-based Traffic Management StrategiesThe following list provides a high-level description of traffic management strategies that have been typically deployed in the US.•Ramp Metering: controlling the flow of vehicles entering a travel stream (typically freeway or highway facilities) to improve the efficiency of merging, and reduceaccidents.•Lane Management (or Managed Lane): improving or facilitating traffic flow in response to changing roadway conditions. Lane management includes controlling use of lanes by vehicle eligibility (carpool or transit), access control, and price.•Variable Speed Limits: dynamically changing speed limit signs to adjust to changing roadway conditions, oftentimes weather related.•Shoulder Use: use of the shoulder by time of day for transit or HOV, and in some instances general purpose traffic, to provide improved mobility along or within congested corridors.•Pricing: managing traffic demand and flow using priced lane facilities, where traffic flow in the priced lane(s) is continuously monitored and electronic tolls are varied based on‘real-time’ demand. Pricing of roadway facilities can collect a toll from all users of thefacility. In the case of high occupancy toll (HOT) lanes, transit and carpools with adesignated number of occupants are allowed to use the priced lanes for free or a reduced rate.•Traveler Information: a variety of types of information provided to travelers (typically via variable message signs) to allow them to make informed travel decisions. Typicaltravel information includes travel times via alternative routes, and occurrence of incidents ahead.The following chapters describe the listed European and US management strategies in greater detail.3.0 US TechniquesAs noted previously, ramp metering and managed lanes comprise the primary types of techniques currently under operation in the US that can be managed actively, with many metropolitan areas employing both ramp metering and managed lane facilities. Ramp meters are stop-and-go traffic signals placed at an on-ramp to control the frequency at which vehicles enter the freeway traffic stream. Managed lane facilities can include high occupancy vehicle (HOV), high occupancy toll (HOT), transit only lanes, and express lanes. They can be concurrent, contraflow or reversible lanes, whether operated part- or full-time.3.1 Ramp MeteringRamp metering, which maintains smooth freeway mainline flow by breaking up platoons of entering vehicles and/or limiting vehicle entry at entrance ramps, has been proposed and implemented in a number of metropolitan areas in and outside the US to mitigate freeway congestion due to merging vehicles.The primary objectives of ramp metering include managing traffic demand to reduce congestion, improving the efficiency of merging, and reducing accidents—all of which lead to improved mainline freeway flow. In some situations, high volume freeway mainline flow can accommodate disbursed merging vehicles, but often cannot handle groups of vehicles at once. Ramp meters may control ramp traffic based on conditions in the field or manually to optimize the release of vehicles entering the freeway facility.Ramp metering that is operated at pre-determined fixed-times of day is typically not considered an active management technique – while its operation can be demand based (on historical demand data), it does not manage the demand in a real-time active manner1. Ramp metering that employs or is managed using an adaptive algorithm that is based on system-wide monitoring that controls the application of ramp metering is considered an active management technique. Ramp meters that are monitored, activated and adjusted based on traffic operations by staff at traffic management centers would be considered actively managed, regardless of the algorithm used by the specific ramp meter.The success of early ramp metering applications in US cities such as Chicago, Los Angeles, Minneapolis and Seattle led to the implementation and expansion of ramp metering systems in many other metropolitan areas in the US including Phoenix, AZ; Fresno, CA; Sacramento, CA; San Francisco, CA; San Diego, CA; Denver, CO; Atlanta, GA; Las Vegas, NV; Long Island, NY; New York, NY; Cleveland, OH; Lehigh Valley area, PA; Philadelphia, PA; Houston, TX; Arlington, VA; Miami, FL; and Milwaukee, WI; as well as in cities in other countries including Sydney, Australia; Toronto, Canada; and Birmingham and Southampton, UK.In 2000 an independent study on ramp metering was conducted in the Minneapolis-St. Paul area (Cambridge Systematics, 2001). The evaluation addressed traffic flow and safety impacts associated with turning off all 430 ramp meters for six weeks. Results released by the Minnesota Department of Transportation showed that without ramp meters there was:1 It could be argued that even though a ramp metering system is set to start and stop at the same time every day, if it is actively monitored by operators and adjusted to adapt to conditions, and/or if the overall ramp metering algorithm is proactive in nature, then it could be considered actively managed.• A nine percent reduction in freeway volume.• A 22 percent increase in freeway travel times.• A seven percent reduction in freeway speeds, which contributed to the negative effect on freeway travel times. The reliability of freeway travel time was found to decline by91 percent without ramp meters.• A 26 percent increase in crashes, which was averaged for seasonal variations. These crashes broke down to a 14.6 percent increase in rear-end crashes, a 200 percent increase in side-swipe crashes, a 60 percent increase in “run off the road” crashes, and an8.6 percent increase in other types of crashes.While ramp metering is more prevalent in the US, it is also employed in Europe. Germany has noted that ramp metering effectively prevents the drop in traffic speeds normally associated with merges and allows for the harmonization of traffic flow on major controlled access roadways. Ramp metering was found to reduce crashes with person and property damage by up to 40 percent, with no negative effects on the adjacent roadway network. On highway A40, a test program from 1998–2002, showed a reduction in accidents of 55 percent, and a 65 percent reduction in severe accidents (translated from “Europe on Course—Telematics on German Roads” German Ministry for Transportation, Construction and Housing 2005).3.2 Managed LanesA popular approach to mobility management in the US is managed lanes, which are defined as dedicated highway facilities or lanes in which operational strategies are implemented and managed. Many of the current strategies are not managed in real time, but with technology advances more real time applications are being considered and implemented. Managed lanes can facilitate traffic flow in response to changing conditions by controlling user eligibility, access and/or pricing. Traditional lane management strategies include high occupancy vehicle (HOV) lanes, high occupancy toll (HOT) lanes, express lanes and reversible lanes. Of the listed managed lane strategies, the only two that can currently be considered as “actively” managed are HOT lanes and express lanes that are dynamically priced.This chapter includes a description of European traffic management techniques with specific examples from Germany, Denmark, the Netherlands, and the United Kingdom. Information, experience and data were highly variable in their availability and therefore, some management techniques are discussed in greater detail than others. All techniques described include a definition of the technique and an associated benefits assessment. When information was available for a given technique, information on operational and safety considerations was included as well.The following European techniques are discussed:•Speed Harmonization/Lane Control: dynamically and automatically reducing speed limits in or before areas of congestion, accidents, or special events to maintain flow and reduce risk of collisions due to speed differentials.•Queue Warning: warning motorists of downstream queues and direct through-traffic to alternate lanes, to effectively utilize available roadway capacity and reduce the likelihood of collisions related to queuing.)• Hard Shoulder Running: using the shoulder (inside or outside) as a travel lane duringcongested periods to minimize recurrent congestion. Hard shoulder running can also be used to manage traffic and associated congestion immediately after an incident.• Junction Control: using variable traffic signs, dynamic pavement markings, and laneuse control to direct traffic to specific lanes (mainline or ramp) based on varying traffic demand, to effectively utilize available roadway capacity and manage traffic flows toreduce congestion• Dynamic Re-routing: changing destination signing to account for downstream trafficconditions• Traveler Information: providing estimated travel time information and other conditionsreports allowing for better pre-trip and in-route decisions3.3 Speed HarmonizationSpeed harmonization (also known as variable speed limits in the US) has been used in theNetherlands and Germany since the 1970s, where it is typically implemented on roadways with high traffic volumes, with a goal of improving traffic flow. In the Netherlands, speedharmonization has been used for many years for the purposes of creating more uniform travel speeds and managing traffic during adverse weather conditions. Lane control displays are used for mitigation of incidents, maintenance and construction. In Germany, approximately 200km (124 miles) of roadway are managed using speed harmonization and lane control. In Denmark, speed harmonization, also referred to as variable speed limits, is deployed to manageconstruction project-relatedcongestion on the ring roadaround Copenhagen.Figure 1 shows speed`harmonization signing in theNetherlands, while Figure 2shows the Dutch signageapplication of the dynamic speedlimit system in the Randstad area.In general, the Europeanexperience has been that at leastone lane control display shouldbe visible at all times formaximum effectiveness. In theNetherlands, gantries supportingspeed controls are typically spaced an average of every 1,600 feet. In Germany, overhead sign bridge spacing is every 3,300 feet (1 km), but varies withinstallation and can extendfarther, depending on sight distance. In addition to sight-distance and geometric considerations, cost may ultimately play a role in the spacing of lane control displays. Gantry spacing for the UKM42 motorway pilot project that implemented a combined speed harmonization and hard Source: Dutch Department of TransportationFigure 1. Speed Harmonization Signing in the Netherlandsshoulder running installation wasapproximately every 1,600 feet(500 meters). Future UK managedmotorway installations mayultimately consider a minimumspacing of approximately 2,600feet (800 meters) and a maximumspacing of 3,300 feet (1000meters) (UK Highways AgencyInterim Advice Note 87/07, 2007).Lane control displays provide theflexibility to help manageincidents or address maintenanceactivities. When congestion is present, the speed limit is dynamically adjusted and displayed. When an incidentoccurs, a lane may be closed byshowing a red ‘X’. Advance notice of an incident is usually provided by indicating to motorists that they should switch out of that lane. This is typically done by using a diagonal arrow pointing to a neighboring lane. In the Netherlands, when an incident occurs, they use a cocked arrow, followed by a red “X” to move drivers out of the lane. On the M42 motorway in the UK, lane control displays are typically enabled for four gantries upstream from the closure or incident, with the first indication being a reduction in standard operating speed, the second a furtherreduction in speed, and the following two gantries using cocked arrows to move drivers out of a closed lane(s).Critical to success of speed harmonization is the traveler’s trust in the real-time operation of the system, including how it is being operated, its reliability, and the sense that it is beingimplemented for a valid purpose that will result in true safety and travel time benefits. Hence traveler information and in many cases queue warning are treated as crucial components for maximizing effectiveness of this technique. Operating the system on a 24/7 basis also generates public trust in the system whenever conditions warrant, and these conditions do not necessarily mean 24/7 staffing of the operation center.Benefits AssessmentGermany has perhaps the longest history of speed harmonization projects, dating back to the 1970’s. Their experience has shown that speed harmonization results in lower accident rates and typically results in a modest (5-10 percent) increase in roadway capacity. This is accomplished in part because the variable speed limits decrease the likelihood of severe congestion by increasing the stability of traffic flow (translated from “Europe on Course—Telematics on German Roads” German Ministry for Transportation, Construction and Housing 2005).When implemented in Germany on the A5 motorway between Bad Homburg andFrankfurt/West, speed harmonization was associated with a 27 percent reduction in accidentswith heavy material damage and a 30 percent reduction in personal injury crashes (Sparmann, Source: Stoelhorst and Havermans Centre for Transport and Navigation, 2008 Figure 2. Dynamic Speed Limits in Randstad Area2006). In Bavaria, accidents were reduced by up to 35 percent, with 31 percent fewer crashes involving injuries (translated from “Europe on Course—Telematics on German Roads” German Ministry for Transportation, Construction and Housing 2005).In the Danish case, as a result of the traffic management applications implemented (speed harmonization, lane management and variable message system)—traffic loads on the surrounding streets were less than expected and accidents did not increase appreciably during the re-construction of the M3 Motorway, even though the existing roadway lanes were narrowed during the construction period (Wendelboe, 2008).England has also applied speed harmonization, known locally as Variable Mandatory Speed Limits (VMSL). On M-42, speed harmonization with hard shoulder running resulted in a seven percent increase in capacity and less overall congestion over the 12-month study period. Statistically valid safety analysis requires three years of data, but the initial results are encouraging (Mott MacDonald Ltd., 2008).Additionally, a number of countries have documented a reduction in vehicle emissions after the implementation of speed harmonization. In The Netherlands, local traffic emission reductions of NOx were in the 20 to 30 percent range and PM10 was reduced by approximately 10 percent in the four test locations. In the UK, initial results found that vehicle emissions were reduced between four and 10 percent depending on the pollutant, and fuel consumption was also reduced by four percent (Mott MacDonald Ltd., 2008).OperationsIn the UK, speed harmonization has been applied to the six-lane M42 motorway (three lanes in each direction) in the West Midlands near Birmingham. In locations where hard-shoulder running is also applied to the outside shoulder, speed harmonization is included for the hard shoulder lane as well. Speed harmonization in the three-lane sections is automatically activated based upon flow and speed thresholds, though operators may adjust the operation if required. In general, speeds are adjusted approximately three gantries (approximately 1,500 meters or nearly 1 mile) back from the area of reduced speeds or an incident.Speed harmonization with hard shoulder running (four lanes) is also based on predefined flow and speed thresholds. However, activation is not automatic, since operators need to ensure that the hard shoulder running lane is not blocked by debris or stopped vehicles. When activated, the speed limit is 50 mph or less (Mott MacDonald Ltd., 2008).Operations for the Washington State Department of Transportation (WSDOT) speed harmonization/queue warning system will be similar to the UK M42 motorway system in that the over-lane speed and lane control signs are automatically activated based on identified thresholds. Under normal congested conditions reduced speeds will be shown on the over-lane signs and reduced speed warnings and information will be provided via side-mount signs and traditional VMS approximately two gantries (1 mile upstream) from congested conditions. The gantry immediately preceding the back of the queue will display the lowest designated speed on the over-lane signs. Over-lane signs on subsequent gantries within congested conditions will be turned off and the shoulder-mount and traditional VMS will provide regulatory and informational messages as necessary. Under incident conditions that include a lane blockage,。

OMG Data-Distribution Service (DDS) - Architectural Overview

OMG Data-Distribution Service (DDS): Architectural OverviewGerardo Pardo-CastelloteReal-Time Innovations, Inc. (RTI)Phone: 1-408-734-4200, x106Email: pardo@Topic Areas Software Architectures, Reusability, Scalability, and StandardsMiddlewareLibrariesandApplication Programming InterfacesFault-Tolerant Hardware and Software TechniquesSummaryThe OMG Data-Distribution Service (DDS) is a new specification for publish-subscribe data-distribution systems. The purpose of the specification is to provide a common application-level interface that clearly defines the data-distribution service. The specification describes the service using UML, providing a platform-independent model that can then be mapped into a variety of concrete platforms and programming languages.This paper introduces the OMG DDS specification, describes the main aspects of the model, compares it with related technologies, and gives examples of the communication scenarios it supports.This paper and presentation will clearly explain the important differences between data-centric publish-subscribe and object-centric client-server (e.g. CORBA) communications, along with the applicability of each for real-time systems.The OMG DDS attempts to unify the common practice of several existing implementations enumerating and providing formal definitions for the Quality of Service (QoS) settings that can be used to configure the service.Publish-subscribe networking is a key component of the Navy Open Systems Architecture (Navy OA) initiative. This talk will also highlight practical publish-subscribe implementations in Navy systems such as LPD 17, SSDS, and DD(X).BackgroundThe goal of the DDS specification is to facilitate the efficient distribution of data in a distributed system. Participants using DDS can “read” and “write” data efficiently and naturally with a typed interface. Underneath, the DDS middleware will distribute the data so that each reading participant can access the “most-current” values. In effect, the service creates a global “data space” that any participant can read and write. It also creates a name space to allow participants to find and share objects. Presentation AgendaReport Documentation Page Form ApprovedOMB No. 0704-0188Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.1. REPORT DATE 01 FEB 20052. REPORT TYPEN/A3. DATES COVERED-4. TITLE AND SUBTITLEOMG Data-Distribution Service (DDS)5a. CONTRACT NUMBER5b. GRANT NUMBER5c. PROGRAM ELEMENT NUMBER6. AUTHOR(S)5d. PROJECT NUMBER5e. TASK NUMBER5f. WORK UNIT NUMBER7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Real-Time Innovations, Inc. (RTI)8. PERFORMING ORGANIZATION REPORT NUMBER9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)10. SPONSOR/MONITOR’S ACRONYM(S)11. SPONSOR/MONITOR’S REPORTNUMBER(S)12. DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release, distribution unlimited13. SUPPLEMENTARY NOTESSee also ADM001742, HPEC-7 Volume 1, Proceedings of the Eighth Annual High Performance Embedded Computing (HPEC) Workshops, 28-30 September 2004. , The original document contains color images.14. ABSTRACT15. SUBJECT TERMS16. SECURITY CLASSIFICATION OF:17. LIMITATION OFABSTRACTUU 18. NUMBEROF PAGES2819a. NAME OFRESPONSIBLE PERSONa. REPORT unclassifiedb. ABSTRACTunclassifiedc. THIS PAGEunclassifiedStandard Form 298 (Rev. 8-98)Prescribed by ANSI Std Z39-18DDS targets real-time systems; the API and QoS are chosen to balance predictable behavior and implementation efficiency/performance. We will note some of these tradeoffs in this paper.Data-Centric versus Object-Centric communications modelsCentral to understanding the need for this new standard is an examination of the fundamental architectural differences between a “data-centric” and “object-centric” view of information communicated in a distributed real-time system.DDS provides a natural counterpoint to the existing well-known CORBA model in which method invocations on remote objects are accessed through an interface defined in the Interface Descriptor Language (IDL). With CORBA, data is communicated indirectly through arguments in the method invocations or through their return values.However, in many real-time applications the communications pattern is often modeled as pure data-centric exchange where applications publish supply or stream) “data” which is then available to the remote applications that are interested in it. Of primary concern is the efficient distribution of data with minimal overhead and the need to scale to hundreds or thousands of subscribers in a robust, fault-tolerant manner. These types of applications can be found in C4I systems, distributed control and simulation, telecom equipment control, and network management.Comparison to Distributed Shared MemoryAdditional requirements of many real-time applications include the need to control QoS properties that affect the predictability, overhead, and resources used. Distributed shared memory is a classic model that provides data-centric exchanges. However, this model is particularly difficult and “unnatural” to implement efficiently over the Internet.Therefore, another model, the Data-Centric Publish-Subscribe (DCPS) model, has become popular in many real-time applications. While there are several commercial and in-house developments providing this type of facility, to date, there have been no general-purpose data-distribution standards. As a result, no common models directly support a data-centric system for information exchange.The OMG Data-Distribution Service (DDS) is an attempt to solve this situation. The specification also defines the operations and QoS attributes each of these objects supports and the interfaces an application can use to be notified of changes to the data or wait for specific changes to occur.Comparison to existing OMG Notification ServiceThis paper will examine the fact that, while it is theoretically possible for an application developer to use the OMG Notification Service to propagate the changes to data structures to provide the functionality of the DDS, doing this would be significantly complex because theNotification Service does not have a concept of data objects or data-object instances nor does it have a concept of state coherence.Comparison to existing High-Level Architecture (HLA) Run-Time Infrastructure (RTI) HLA, also known as the OMG Distributed Simulation Facility, is a standard from both IEEE and OMG. It describes a data-centric publish-subscribe facility and a data model. The OMG specification is an IDL-only specification and can be mapped on top of multiple transports. The specification address some of the requirements of data-centric publish subscribe: the application uses a publish-subscribe interface to interact with the middleware, and it includes a data model and supports content-based subscriptions.However, the HLA data model supports a specialization hierarchy, but not an aggregation hierarchy. The set of types defined cannot evolve over time. Moreover, the data elements themselves are un-typed and un-marshaled (they are plain sequences of octets). HLA also offers no generic QoS facilities.ApplicationsThis paper will describe the successful implementation of data-centric publish-subscribe communications in distributed modeling and simulation (M&S) as well as deployed Navy systems (pending release permissions). The presentation can include examples (depending on audience interest and familiarity) such as:Ship: Raytheon/Lockheed Martin LPD-17 Programtactical communications ProgramGround: CLIP/LINKAir: F-35 JSF EW SubsystemSpace: NASA Robonaut Program。

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Prepared for the Thirty-ninth Annual Conference of the Society of the Plastics Industry (SPI) Reinforced Plastics/Composites Institute, Houston, Texas, January 16-20, 1984.
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SIMPLIFIED COMPOSITE MIC ROME CHANICS EQUATIONS FOR STRENGTH, FRACTURE TOUGHNESS, IMPACT RESISTANCE AND ENVIRONMENTAL EFFECTS
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eetec h nica lno tetc h D U.S. ocum e nt is a vailable to the pub lic thro ug h the National Technica l Info rm ation S ervice, S pring field, V irginia 22161D e p a rtm e n t o f Tra n sp o rta tion Federal Aviation Adm inistrationW illiam J. H u gh es Te ch nica l Ce n te rNOTICEThis document is disseminated under the sponsorshipof the U.S. Department of Transportation in the interest of information exchange. The United States Government assumes no liability for the contents or use thereof.The United States Government does not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the objective of this report.Technical Report Documentation Page 1. Report No. DOT/FAA/CT-TN01/06 2. Government Accession No. 3. Recipient’s Catalog No.5. Report Date February 2001 4. Title and SubtitleDisplay Concepts For En Route Air Traffic Control6. Performing Organization Code ACT-5307. Author(s) Ulf Ahlstrom, Ph.D., ACT-540, Joshua Rubinstein, Ph.D., AAR-510, Steven Siegel, Ph.D., Logicon/FDC, Richard Mogford, Ph.D., NASA Ames Research Center, andCarol Manning, Ph.D., AAM-5108. Performing Organization Report No. DOT/FAA/CT-TN01/06 10. Work Unit No. (TRAIS)9. Performing Organization Name and Address Federal Aviation Administration William J. Hughes Technical Center Atlantic City International Airport, NJ 08405 11. Contract or Grant No.13. Type of Report and Period CoveredTechnical Note 12. Sponsoring Agency Name and Address Civil Aeromedical InstituteHuman Resources Division (AAM-500)6500 S. Mc Arthur Blvd.Oklahoma City, OK 7312514. Sponsoring Agency Code AAM-50015. Supplementary Notes16. Abstract Previous research in the domain of air traffic control (ATC) has explored factors that describe the complexity facing a controller.Based on this research, new technologies and procedures have been developed that may aid the controller and reduce the complexity in ATC. Most of these technologies were designed to reduce ATC complexity associated with air traffic density, identification andresolution of conflict situations, and the operational efficiency of the human-machine interface. The purpose of the present study was to explore and prototype new display enhancements that may reduce complexity in ATC. A team of researchers from the Human Factors Branch (ACT-530) of the Federal Aviation Administration William J. Hughes Technical Center and the Human Resources Research Division (AAM-500) of the Civil Aeromedical Institute (CAMI) identified four complexity factors as being suitable for a graphical enhancement. These factors were the effects of weather on airspace structure, the effects of active Special Use Airspace(SUA), the effects of the number of transitioning aircraft, and the effects of the reliability of radio and radar coverage. We conducted a user evaluation of the display enhancements and their possible impact on ATC complexity. Two supervisors and 13 Full Performance Level controllers from the Jacksonville Air Route Traffic Control Center participated as observers in this evaluation. The results of the user evaluation showed that the controllers supported earlier research that identified weather, SUA, transitioning aircraft, and reliability of radio and radar coverage as factors that increase ATC complexity. The controllers favored the proposed display enhancements. More importantly, the controllers predicted a substantial reduction in their job complexity from the enhancements. Based on these findings, we recommend a formal test simulation of the proposed enhancements to determine their efficacy for reducing taskcomplexity in ATC operations. We also recommend further studies to determine the optimal colors for each display enhancement for use in operational systems.17. Key WordsComplexity FactorsDisplay Concepts18. Distribution StatementThis document is available to the public through the National Technical Information Service, Springfield, Virginia, 22161 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 28 22. PriceForm DOT F 1700.7 (8-72) Reproduction of completed page authorizedAcknowledgmentThe work presented in this study was funded by the Human Resources Research Division (AAM-500) of the Civil Aeromedical Institute (CAMI) and is the result of a sub-task in a joint project between the AAM-500 and the William J. Hughes Technical Center National Airspace System Human Factors Branch (ACT-530). We gratefully acknowledge the help from Supervisor Phil Bassett, Jacksonville Air Route Traffic Control Center, who provided invaluable support and subject matter expertise during this project. We would also like to thank Michael D. Snyder, Federal Data Corporation, for his help and support with the use of the Systematic Air Traffic Operations Research Initiative System and Lou Delemarre, ACT-510, for providing us with the Next Generation Weather Data.Table of ContentsPage Acknowledgment (iii)Executive Summary (vii)1. Introduction (1)1.1 Background (1)1.2 Purpose (2)2. Method (2)2.1 Participants (2)2.2 Apparatus (2)2.3 Procedure (2)2.3.1 Identification of Complexity Factors (2)2.3.2 Initial Display Enhancements (3)2.3.3 Pilot Study (3)2.3.4 Refined Display Enhancements (4)2.3.5 Primary Study (8)3. Results (9)3.1 Weather Display (9)3.2 Special Use Airspace (11)3.3 Transitioning Aircraft (12)3.4 Navigational Aid Outages (14)4. Conclusions (16)5. Recommendation s (17)References (18)AppendicesA - Factors Contributing to ATC Complexity (from Mogford et al., 1994)B - Factors Contributing to ATC Complexity (from Wyndemere, Inc., 1996)C - Color Specification of Display FeaturesList of IllustrationsFigures Page1. An Illustration of the Weather Display Enhancement (5)2. An Illustration of the Color Coding of Active SUAs (6)3. Color Coding of Overflights, Airport Destination, and Navaid Outage (7)4. Controller Ratings of Weather Factors Impact (10)5. Controller Ratings of Weather Display Complexity Reduction (10)6. Controller Ratings of Active SUA Impact (11)7. Controller Ratings of Color Coding of Active SUA Complexity Reduction (12)8. Controller Ratings of Transitioning Aircraft Impact (13)9. Controller ratings of Color Coding of Over Flights and Airport Destinations ComplexityReduction (14)10. Controller Ratings of Navaid Outages Impact (15)11. Controller Ratings of Graphical Representations of Navaid Outages ComplexityReduction (16)Executive SummaryPrevious research in the domain of air traffic control (ATC) has explored factors that describe the complexity facing a controller. Based on this research, new technologies and procedures have been developed that may aid the controller and reduce complexity in ATC. Most of these technologies were designed to reduce ATC complexity associated with air traffic density, identification and resolution of conflict situations, and the operational efficiency of the human-machine interface. The purpose of the present study was to explore and prototype new display enhancements that may reduce complexity in ATC.A team of researchers from the National Airspace System Human Factors Branch (ACT-530) of the Federal Aviation Administration William J. Hughes Technical Center and the Human Resources Research Division (AAM-500) of the Civil Aeromedical Institute (CAMI) reviewed earlier research by Mogford, Murphy, Roske-Hofstrand, Yastrop, & Guttman (1994) and Wyndemere, Inc. (1996) to identify complexity factors that could be addressed by a display enhancement. Four complexity factors were identified in a pilot study as suitable for a graphical enhancement: weather effects on airspace structure, the effects of active Special Use Airspace (SUA), the amount of transitioning aircraft, and the reliability of radio and radar coverage.To evaluate the usability of our display enhancements and their possible impact on ATC complexity, the team conducted a user evaluation at the Jacksonville Air Route Traffic Control Center. Two supervisors and 13 Full Performance Level controllers participated as observers in this evaluation. We showed the prototype to the controllers during structured interviews and collected user ratings on the acceptability of the display enhancements together with ratings on the degree by which the enhancements would reduce ATC complexity. For each of the four complexity factors, the controllers also explained what actions they have to take when confronted with the factor, how frequently each factor adds difficulty to controlling traffic, and to what extent the complexity factor impacts on their job.The results of the user evaluation showed that the controllers supported earlier research that identified weather, SUA, transitioning aircraft, and reliability of radio and radar coverage as factors that increase ATC complexity. The controllers were very much in favor of the proposed display enhancements. Most importantly, the controllers predicted a substantial reduction in their job complexity from the enhancements.Based on these findings, we recommend a formal test simulation of the proposed enhancements to determine their efficacy for reducing task complexity in ATC operations. We also recommend further studies to determine the optimal colors for each display enhancement for use in operational systems.1. IntroductionThe purpose of the Air Traffic Control (ATC) system is to provide a safe, efficient flow of air traffic from origin to destination. Therefore, it is important to identify and reduce the factors that increase the complexity of ATC operations. Mogford, Guttman, Morrow, and Kopardekar (1995) described ATC complexity as having both physical aspects (e.g., sector size and airway configuration) and dynamic aspects relating to the movement of aircraft through the airspace (e.g., the number of climbing and descending aircraft). Factors such as equipment, environment, and controller ability and experience further influence the degree of complexity. Increases in complexity have been reported to result in increases in controller workload and, consequently, more operational errors (Mogford et al.; Rodgers, Mogford, & Mogford, 1998; Stein, 1985). This research examines methods of reducing ATC complexity and thus reducing controllers’ workload and errors.1.1 BackgroundSeveral studies have explored factors that describe the complexity facing a controller. For example, Mogford, Murphy, Roske-Hofstrand, Yastrop, and Guttman (1994) proposed 15 factors that seem to be of significant importance (see Appendix A). Wyndemere, Inc. (1996) proposed 19 factors believed to contribute to complexity (see Appendix B).New technologies and procedures have been developed to reduce job complexity by aiding the controller in ATC. For instance, new Traffic Management Unit (TMU) technologies allow TMU specialists to predict when aircraft will arrive at a particular sector and reroute aircraft from overly dense sectors. These technologies attempt to reduce ATC complexity associated with air traffic density. Conflict probes, such as the User Preferred Routing Tool of the Center-TRACON Automation System (CTAS) and the User Request Evaluation Tool (URET), allow controllers to predict and resolve many conflicts in a short time and test possible resolutions (Carrigan, Dieudonne, & MacDonald, 1997). These tools attempt to reduce complexity associated with identifying and resolving conflict situations.Attempts have also been made to reduce complexity by enhancing the human-machine interface in the ATC environment. The Operational Display and Input Development (ODID) system, with a windows-based graphical user interface, demonstrated promising ATC concepts (Skiles, Graham, Marsden, & Krois, 1997). A controller operational review showed that the ODID dialogue design simplified information retrieval and data entry with simple mouse operations and available pop-up menus. Along similar lines, systematic studies of the use of color in ATC displays have developed guidelines for implementations that will reduce the controller’s information processing by enhancing display information (Reynolds, 1994). Using seven visual layers with different color palettes, Reynolds created displays that emphasized the most important data without increasing the overall complexity. As a promising system for future display enhancements, the Three-Dimensional Volumetric Display could ease the controller’s workload even further than what is possible with current 2-D display technology (Hanson, 1997). For example, the Three-Dimensional Volumetric Display can integrate all of the components of a complicated airspace onto a single display.1.2 PurposeThis study explored and prototyped new display enhancements that may reduce complexity in ATC. It consisted of five project phases: identification of complexity factors, prototype development of display enhancements, a pilot study to implement and evaluate the enhancements, refinement of the display concepts, and the primary study in which the refined enhancements were finalized and evaluated.2. MethodResearch psychologists from the National Airspace System Human Factors Branch (ACT-530) of the Federal Aviation Administration William J. Hughes Technical Center (WJHTC) and the Human Resources Research Division (AAM-500) of the Civil Aeromedical Institute (CAMI) identified complexity factors that could be addressed by a graphical enhancement. We reviewed earlier research by Mogford et al. (1994) and Wyndemere, Inc. (1996) to identify complexity factors that could be addressed by a display enhancement. The team explored and prototyped new display enhancements that may reduce complexity in ATC.2.1 ParticipantsTwenty controllers and supervisors were involved in evaluating the display enhancements discussed in this report. Five Full Performance Level (FPL) en route controllers participated in the pilot study. Two were from Minneapolis Air Route Traffic Control Center (ARTCC) (ZMP), one was from Jacksonville ARTCC (ZJX), and two were from Houston ARTCC (ZHU). Two supervisors and 13 FPL controllers (mean experience = 17 years, SD = 7.2) from ZJX participated in the primary study.2.2 ApparatusThe research team developed the prototypes in Macromedia Director™ 6.5 (Macromedia, 1997) using a Gateway 300 MHz Pentium II computer and a 21 in. color monitor. The pilot study was conducted using this equipment. For the development of actual ATC scenarios for the primary study, we recorded a System Analysis Report (SAR) tape from the Host computer at ZJX. After Data Analyses and Reduction Tool (DART) and National Track Analysis Program processing of the SAR tape, we loaded the resulting files into the Systematic Air Traffic Operations Research Initiative (SATORI) System, captured an ATC scenario, and imported it into Director. The primary study used two portable Gateway notebooks and an external 15-in. color monitor.2.3 Procedure2.3.1 Identification of Complexity FactorsThe research team identified five complexity factors that might be ameliorated by display enhancements: weather effects on airspace structure, the effects of Special Use Airspace (SUA), transitioning aircraft, the reliability of radio and radar coverage, and the workload associated with the number of required procedures that the controller must perform. Discussions with twosubject matter experts and informal interviews with Air Traffic Control Specialists (ATCSs) indicated the importance of these five factors regarding air traffic complexity. Furthermore, we chose these five factors because they presented an attainable combination for this first prototyping effort.2.3.2 Initial Display EnhancementsTo develop the initial display enhancements, we visited Jacksonville (ZJX) and Boston (ZBW) ARTCCs to gather information about the different weather display systems used by controllers, TMU personnel, supervisors, and meteorologists. We also examined the procedures used for activating SUA. Using a generic air traffic scenario (Guttman, Stein, & Gromelski, 1995), we developed display concepts for a six-level weather display, color coding of active SUA, color coding of climbing and descending aircraft, graphical representations of radio and radar outages, and an on-screen representation of standard and temporary procedures.2.3.3 Pilot StudyTo receive feedback on our initial display enhancements, five en route controllers participated in a pilot study at the WJHTC Research Development and Human Factors Laboratory. The purpose of the study was to receive feedback on our initial display enhancements so that we could optimize each separate prototype. The controllers participated in two groups during the study. One group consisted of the two controllers from Minneapolis (ZMP) ARTCC and the controller from Jacksonville (ZJX) ARTCC; a second group consisted of the two controllers from Houston (ZHU) ARTCC. Prior to showing the prototypes to the controllers, we discussed the purpose of the study. We asked them to explain what actions they normally take when confronted with each complexity factor, how frequently each factor adds difficulty to controlling traffic, and whether the display enhancements would reduce the complexity associated with the factor. After these instructions, we presented the five separate prototypes to the controllers and recorded their feedback. The controllers’ responses are summarized as follows.a. All controllers complained about their current weather system, its lack of accuracy, andtheir inability to pass on any weather information to the pilots. Usually, the pilots tell the controller where the weather is located. All of the controllers could see the benefit of aweather display as shown in the prototype. They also thought that all the information that would be needed (i.e., the level of precipitation, upper-level winds, cloud tops, andanimated weather prediction) when controlling traffic was displayed in the prototype.b. Controllers were very much in favor of the color coding of SUAs and the text-basedinformation about altitudes and activation times.c. The display concept of having climbing and descending (i.e., transitioning) aircraft codedin different colors yielded mixed reactions from the controllers. Three of the fivecontrollers saw a benefit of having descending and climbing aircraft in different colors,whereas, the other two controllers saw a greater benefit in having overflight color coded.It seemed that color coding would be useful to the controllers, but several factors (e.g.,sector characteristics and traffic flow) determine what would be useful to color code.d. All five controllers were strongly in favor of a graphical representation of a navigationalaid (navaid) outage directly on the situation display. However, only two of the controllers liked the graphical representation of an area that has minimal radio coverage. The other three argued that such a representation would be unnecessary because controllers learnwhere these areas are as they work their sector.e. The controllers liked the concept of having standard and temporary procedures availablein a pop-up window. However, they all agreed that this is not a problem in their dailywork and, therefore, would contribute very little compared to how these procedures arestored currently. These controllers reported that this enhancement would not reduce the complexity of their task.2.3.4 Refined Display EnhancementsThe revised prototype contains an enhanced weather display (Figure 1). As a basis for the weather display, we incorporated some display information that is similar to that found in the Integrated Terminal Weather System. The weather display depicted six independent levels of precipitation with an animated prediction of weather cell movements. We used Next Generation Weather Radar data from the National Weather Service to produce the six levels of precipitation. The animated weather prediction consisted of 17 frames of weather and was intended to give information about the weather cell movements during a 30-minute period. In addition to the graphical representation, the display presented text-based information about the intensity of precipitation, thunderstorms, turbulence, radar echo tops, and upper level winds in an information message window. The weather intensity ranged from level 1 to level 6. When levels 4-6 are encountered, the majority of aircraft will request alternate routings. Levels 1-3, on the other hand, are generally navigable and associated with minor turbulence. They also can be used to predict the build up of increasingly severe weather. Thunderstorm information is critical to flight safety and is associated with severe weather phenomena including hail, lightning, and moderate to severe turbulence. Echo tops are directly related to thunderstorm intensity and are defined in the prototype by their highest altitude level. Upper level winds are identified by altitude, direction, and speed. For example, FL290 310 25G35 indicates the winds at flight level (FL)290 are from the northwest (310) at 25 knots gusting to 35 knots. This wind information is useful to the pilot because it indicates the possibility of turbulence and can be used to calculate fuel consumption.Figure 2. An illustration of the color coding of active SUAs (a color version of this picture can be found at /act-500/hfl/complexity/CAMI_sua.JPG).FL150). Sometimes, however, only a specific section of the total airspace volume over an SUA was activated at a given time. Thus, aircraft would then be allowed into this area below or above the activated airspace volume. Investigators need more research, however, to implement possible display solutions for these more complex situations.Figures 3A and 3B demonstrate the use of color coding data block text to denote specific aircraft transitions. For the Cedar Key Sector, the demonstration included two types of color coding that seem to be useful for this specific sector: overflights (3A) and airport destination (3B). The data block for each en route aircraft consisted of three lines of data text. The first line in the data block showed the callsign (i.e., DAL705 is Delta Airlines 705). The second line contained altitude information. The third line contained ground speed, destination airport identification, and the computer identification number. In the prototype, a yellow coding of the second line in the data block indicated that the aircraft was an overflight. An overflight is any aircraft that will transition the sector without landing. An orange letter (T) as the destination airport identification in the third line indicated that the aircraft was on a route to Tampa, and a blue letter (Q) indicated that the aircraft was on a route to Sarasota. Although several other airport destinations are possible within the sector, the idea is to use color coding to highlight important target groups in the traffic flow that affect controller actions. The prototype demonstrated how the user can select either one or a combination of the two color schemes, all depending on whether the traffic situation at hand makes it useful to display this information. An important issue concerning the use of color coding in data blocks has to do with the amount of text being colored and the specific way it is implemented. Currently, no data are available on the optimal implementation for operational use; more research is needed to investigate this issue.Figure 3. An illustration of the color coding of (a) overflights, (b) airport destination, and (c) a graphical representation of a navaid outage (color versions of these pictures can be found at /act-500/hfl/complexity/CAMI_color_coding.JPG).Because the ARTCC radar system is mosaic in its design, the system provides redundancy and target integrity even if one radar site fails. Only in the case where multiple, remotely located radar sites fail will the potential for reduced or total loss of radar coverage occur. However, failure of a single radar site can result in reduced radar coverage at lower altitudes. A more common problem than loss of radar coverage is the failure of navaids. When a navaid outage occurs at a location that is commonly used for aircraft navigation, the controller must take action by either vectoring or having the aircraft use alternate navaids. These situations will increase controller workload and might also increase the complexity in controlling traffic. Area Navigation (RNAV) equipped aircraft, however, are unaffected by a navaid outage and do not need help from the controller for navigation. Figure 3C demonstrates a graphical depiction of a navaid outage on the sector map. In addition to the graphics, specific text-based information is displayed in a system message window. When the navaid is back in service again, the graphic disappears from the sector map and information about the status change is displayed in thesystem message window. In this way, a constant reminder of a navaid outage is displayed on the sector map, and, when there is a change of the navaid status, the new information is conveyed to the controller directly.The pilot data were from a relatively small number of controllers (5), and we presented the display modifications in separate prototypes. To assess these enhancements further, we conducted a second, larger (primary) study in which we integrated all the display modifications together. In this way, we more accurately simulated how controllers would view the display concepts on the job. In response to the controllers’ feedback in the pilot study, the prototype constructed for the primary study did not include graphical representations of areas that have minimal radio coverage or the on-screen representation of standard and temporary procedures. The refined prototype contained a 15-minute ZJX ATC scenario from the Cedar Key Sector. Cedar Key Sector 14 suited the needs of the study because it regularly experiences weather effects, has large areas of SUA, and contains many complex traffic routes with heavy traffic. The demonstration contained the Cedar Key traffic scenario, a weather display, color coding of active SUA, examples of color coding of transitioning aircraft, and a graphical representation of a navaid outage.Although the use of color in ATC displays is far from resolved (Cardosi, 1998; Galushka, 1997), the pilot study demonstrated a potentially successful application. Graphics and colors can be used to emphasize important data and possibly to reduce complexity in ATC operations. However, we do not suggest a particular color palette for display enhancements or visual layers. The display concepts used colors that do not interfere with one another when viewed on a black background in normal office lighting conditions. For example, as the data blocks moved over weather cells or color-coded warning areas, there was sufficient chromatic contrast so as to ensure information legibility. (For a description of the colors used in the prototype, see Appendix C.) Further studies are necessary to evaluate specific color palettes for our display enhancements in operational systems and what consequences they might have on information retrieval and overall display complexity.2.3.5 Primary StudyDuring the primary evaluation, the controllers participated one at a time sitting in front of the computer monitor as the research team instructed them on how to interact with the prototype. We demonstrated each menu function in the prototype to the controller: how to toggle weather levels on and off; how to control the animated weather prediction; how to use the three options for data-block color coding; and how to stop, forward, and rewind the traffic scenario. After the controller had interacted with all display enhancements in the prototype, he or she gave feedback regarding the acceptability of the enhancements during structured interviews and using rating scales. For each of the four complexity factors, the controllers explained what actions they normally take when confronted with the factor, how frequently each factor adds difficulty to controlling traffic, and to what extent it impacts their job. The third question used a 5-point rating scale in which a rating of 1 implied no impact and a rating of 5 implied a very high impact. Likewise, for each of the four display enhancements, controllers evaluated to what extent it。