Abstract:
Increasing traffic volumes and a deteriorating transportation infrastructure have stimulated the development of new systems and methods to accelerate the construction of highway bridges. Precast concrete bridge components offer a potential alternative to conventional reinforced, cast-in-place concrete components. The use of precast components has the potential to minimize traffic disruptions, improve work zone safety, reduce environmental impacts, improve constructability, increase quality, and lower life-cycle costs. This study compared two precast concrete bridge pier systems for rapid construction of bridges in seismic regions. One was a reinforced concrete system, in which mild steel deformed bars connect the precast concrete components and provide the flexural strength of the columns. The other was a hybrid system, which uses a combination of unbonded post-tensioning and mild steel deformed bars to make the connections. A parametric study of the two types of systems was conducted using nonlinear finite element models to investigate the global response and likelihood of damage for various frame configurations. On the basis of this study, a practical method was developed to estimate maximum seismic displacements from the cracked section properties of the columns, the elastic design displacement response spectrum, and the base-shear strength ratio. The results of the global nonlinear finite element analyses suggest that the systems have the potential for good seismic performance. Further analytical and experimental research is needed to investigate the constructability and seismic performance of the connection details.

Authors:
Hieber,D. G., Wacker,J. M., Eberhard,M. O., Stanton,J. F.

Keywords:
Alternative, bridge, bridges, columns, concrete, concrete bridge, connections, constructability, construction, cost, costs, damage, design, developed, development, environmental, environmental impact experimental, finite element, highway, impact, impacts, infrastructure, methods, models, performance piers, precast, precast concrete, prestressed concete, quality, Rapid construction, Regions, reinforce concrete, research, response spectra, response spectrum, safety, seismic, seismic performance, steel strength, Study, substructures, System, systems, traffic, traffic volumes, trasportation, volume

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/611.1.pdf http://wsdot.wa.gov/Research/Reports/600/611.1.htm

Abstract:
This project performed extensive study and systematic research on the application of the Highway Development and Management system (HDM-4) to the Washington State Department of Transportation (WSDOT) highway system. Data processing, testing, calibration, and analysis were executed to provide the WSDOT with a new budget planning tool. HDM-4 flexible pavement deterioration models were calibrated with the assistance of the Washington State Pavement Management System. A method to calibrate concrete pavement distress models is proposed. This research also explored the application of HDM-4 analysis at the project, program, and strategic levels. The applications include prediction of pavement conditions during a defined analysis period, calculation of required budgets for optimal pavement conditions and maximum economic indicators, establishment of optimized work programs under varying levels of constrained budgets, and other applications for WSDOT.

Authors:
Li,J., Muench,S. T., Mahoney,J. P., Pierce,L., Sivaneswaran,N.

Keywords:
HDM-4, models, pavement maintenance, pavement management, pavement performance, Pavement preservation, vehicle operating costs, research, highway, development, management, management system, Washington, Washington state, transportation, WSDOT, data, calibration, analysis, planning, pavement, deterioration, concrete, program, applications, prediction, condition, indicators

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/588.1.pdf http://wsdot.wa.gov/Research/Reports/500/588.1.htm

Abstract:
The SR99-Spokane Street Over-crossing is located in Seattle, Washington, and was built in the late 1950s. Its construction is mostly of reinforced concrete; the reinforcement detailing is poor by modern seismic standards, particularly with respect to confinement, and the underlying soils are also weak. Furthermore, the structure contains many "outrigger bents", in which columns are displaced from their ideal locations to accommodate passage of railroad tracks beneath the structure. These outrigger bents cause significant asymmetry in the structure that could lead to unusual and undesirable seismic response. In this study, the seismic response of the structure was evaluated analytically and seismic retrofit strategies were developed and evaluated. In a companion experimental study by Washington State University (WSU), the as-existing structure was investigated by testing scale models of representative bents, and one retrofit strategy was also tested. In this report, modeling approaches are discussed in detail, and the results of evaluations of the as-existing structure as well as the retrofit strategies are presented. Some components of the structure (e.g. the deck, the already-jacketed columns and the soil-foundation-structure system) were found to be critical to an accurate determination of response and were therefore modeled in some detail. Site-specific ground motions at three different hazard levels were used. The structure was found to be vulnerable, especially to the 72- and 475-year ground motions. The knee-joints that connect the outrigger beams and columns were found to be the most critical components, and their vulnerability was shown to be influenced by the type of retrofit performed on the outrigger column. Retrofit strategies included some designed to increase the strength and ductility of the components, and some intended to reduce the demands on them.

Authors:
Inouye,B., Lehman,D. E., Stanton,J. F., Kramer,S. L.

Keywords:
columns, concrete, construction, ductility, evaluation, experimental, hazard, ITS, knee-joints, modeling, models, outriggers, reinforced concrete, reinforcement, retrofit, seattle, seismic, seismic response, soil-structure interaction, strength, Washington, Washington state

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/596.1.pdf http://wsdot.wa.gov/Research/Reports/500/596.1.htm

Abstract:
Cotton duck bearing pads (CDP) are sometimes used to support loads and accommodate movements and rotations at bridge bearings. CDP are preformed elastomeric pads consisting of thin layers of elastomer interlaid with fabric, and they are manufactured under Military Specifications with limited guidance from the AASHTO. The behavior of these CDP bearing pads was experimentally evaluated to establish design models for predicting this behavior, to determine the variation in behavior expected with different bearing pad manufacturers, and to develop design recommendations. This research is a follow-up study of an earlier research program sponsored by Arkansas State University.CDP bearing pads from three different manufacturers were tested, and the test program included dynamic and static (or monotonic) tests of bearings in shear, compression,and rotation. In general, the static tests were used to evaluate strength, stiffness, deformation limits, and general pad behavior. The dynamic tests examined durability and performance under repeated loading and deformation.The results of this test program were used to develop design recommendations, and an appendix includes a draft of proposed wording for modification of the AASHTO LRFD Specifications to include these design recommendations. In addition, a spreadsheet was developed in Microsoft EXCEL to accomplish the calculations necessary to complete the design.

Authors:
Lehman,D. E., Roeder,C. W., Larsen,R., Curtin,K.

Keywords:
cotton duck bearing pads, CDP, bridge bearings, bridge design, loads, bridge, specifications, specification, behavior, design, models, research, program, tests, strength, durability, performance

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/569.1.pdf http://wsdot.wa.gov/Research/Reports/500/569.1.htm

Abstract:
The purpose of this research was to explore the relationship between roadway and roadside accidentrates for Washington State highways to improve the Washington State Department of Transportation's(WSDOT) process of modeling roadway and roadside accident rates and to arrive at possible improvements in the efficiency of WSDOT's safety project programming process.The project tested the use of the seemingly unrelated regression estimation (SURE) model to modelthe roadway and roadside simultaneously. The theoretical advantage of the SURE approach is that it does not impose any a priori assumptions on the explicit linkage between roadway and roadside accident rates, and there is no theoretical support for explicit linkage, either. The data used to derive this model were from a random sample of 500 one-mile sections from the Washington State highway system. Traffic dataincluded traffic volumes, truck compositions, AADT, traffic speeds, and other relevant information.Geometric data included lane, shoulder, median, curve, and intersection information. Historical weather data such as monthly precipitation and temperature were collected from the National Oceanic and Atmospheric Administration database.In comparing significant explanatory variables between the roadway accident rate and roadsideaccident rate models, very few variables were common. This confirms that it is preferable to specifyseparate functional forms for roadway and roadside accident rates. Empirical results indicated thatcorrelation between roadway and roadside accident rates was insignificant, indicating that efficiency gainsfrom the SURE model would be minimal. The important finding from a programming standpoint is thatjointly modeling the roadway and roadside simultaneously would not result in significant efficiencyimprovements in comparison to the current state-of-the-practice in Washington State.

Authors:
Chayanan,S., Nebergall,M., Shankar,V., Juvva,N., Ouyang,Y.

Keywords:
roadway, roadside, accident rates, safety programming, research, Washington, Washington state, highway, transportation, WSDOT, modeling, safety, regression, linkage, data, traffic, traffic data, volume, truck, speed, median, temperature, database, models

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/562.1.pdf http://wsdot.wa.gov/Research/Reports/500/562.1.htm

Abstract:
The pervasive problem of restoring fish runs to their natal streams is characterized in many regions of Washington by improperly placed culverts. The replacement of these fish migration barriers requires knowledge of design flows: floods for structural safety and migration season high and low flows. High flows block fish passage with velocities that exceed their swimming capabilities. During low flows, the migration barrier is caused by a lack of enough water depth to support the bodies of the fish. The estimation of these fish passage and safety flows in ungaged streams is impeded in eastern Washington due to: the wide range of conditions (5 to 110 inches per year of precipitation); diverse geology and soils; a lack of stream-gaging stations with long-term records; changes in land use; and the seasonal impacts of irrigation diversions and well on the remnant flows. Past efforts to estimate these flows have not been successful. Therefore, the WSU project was undertaken to model the high migration season flow in all of eastern Washington. In addition, WSU established 20 stream-gaging stations on salmon streams along the east side of the Cascade Mountains plus the Blue Mountains. Our complementary project was developed to estimate other design flows in the Water Resource Inventory Areas and 49, in which the WSU gage sites are located. United States Geological Survey (USGS) gage records in those (and in and 47) were used to develop our models that estimate the following statistical flows: 100-year, 25-year and 2-year daily and peak floods; the average annual flow and its variability; ranges of mean monthly flows (maximum, average and low); the 7-day average, 2-year, 10-year, 20-year low flow; and the 30- and 60-day average low flows. The model results are, for the most part, very good. The standard error of estimate ranges are: for floods, 2 -37%; average annual flow, 10-37%; maximum annual flow, 6 -14%; annual flow, 13 -23%; and flows, 3 -22%. Monthly average flows reflected the strong influences of seasonal variability and irrigation withdrawals: due to winter frozen Iowa flows (3%)in the Entiat,-Wenatchee Region, and August low flows (242%) in the Blue Mountains due to irrigation. All flow estimation equations were based on USGS stream-gaging data from continuous located in the located in the WRIA'S.

Authors:
Orsborn,J. F., Orsborn,M. T.

Keywords:
Annual, barrier, barriers, condition, culvert, culverts, data, design, design flows, developed, equations, Error, fish, fish passage, flood, flow, hydrologic models, impact, impacts, ITS, land use, land-use, model, models, project, safety, salmon, season, seasonal, soil, structural safety, survey, velocity, Washington, winter

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/545.2.pdf http://wsdot.wa.gov/Research/Reports/500/545.2.htm

Abstract:
This research project was an effort to improve our understanding of the internal stress-strain distribution in GRS retaining structures. Our numerical modelling techniques utilized a commercially available element program, FLAC (Fast Lagrangian Analysis of Continua). In this research, we investigated and appropriately considered the plane strain soil properties, the effect of low confining pressure on the soil dilation angle, and in-soil and low strain rate geosynthetic reinforcement properties.Modeling techniques that are able to predict both the internal and external performance of GRS walls simultaneously were developed. Instrumentation measurements such as wall deflection and reinforcement strain distributions of a number of selected case histories were successfully reproduced by our numerical modeling techniques. Moreover, these techniques were verified by successfully performing true "Class A" predictions of three large-scale experimental walls.An extensive parametric study that included more than 250 numerical models was then performed to investigate the influence of design factors such as soil properties, reinforcement stiffness, and reinforcement spacing on GRS wall performance. Moreover, effects of design options such as toe restraint and structural facing systems were examined. An alternative method for internal stress-strain analysis based on the stress-strain behavior of GRS as a composite material was also developed. Finally, the modeling results were used to develop a new technique for predicting GRS wall face deformations and to make recommendations for the internal stability design of GRS walls.

Authors:
Holtz,R. D., Lee,W. F.

Keywords:
analysis, behavior, design, experimental, FLAC, geosynthetic, geotechnical, materials, modeling, models, performance, prediction, pressure, program, reinforcement, research, retaining wall, retaining walls, stability, structures, systems, walls

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/532.1.pdf http://wsdot.wa.gov/Research/Reports/500/532.1.htm

Abstract:
Funded by the 1987 Intermodal Surface Transportation Efficiency Act, the Strategic Highway Research Program (SHRP), was a five year, $150 million research program to improve the performance of the nation's roads by addressing four key areas: concrete and structures; highway safety and maintenance; asphalt; and long-term pavement performance. Nearly one-third of the $150 million was allocated for the study of asphalt, specifically to develop performance based specifications that would relate material properties of the binder and the mix to field performance. Superpave (Superior PERforming asphalt PAVEments) encompasses the products of the SHRP asphalt research program and consists of three interrelated elements: an asphalt binder specification with supporting tests; a mix design and analysis system with supporting tests; and performance prediction models. This report is a compilation and synthesis of Washington DOT's (WSDOT) experience with selected components and concepts of the SHRP/Superpave technology to include the following: performance graded (PG) binder usage and specification validation; gyratory mix design; the Superpave Shear Test (SST); and field performance of the Superpave mixes.Binders typically specified by WSDOT (AR400OW and PBAs -2, -5, -6. -6GR) were classified in terms of five Superpave performance grades: PG 58-22; 64-22; 64-28; 64-34; and 70-28. Although data from 171 weather stations suggest that as many as 6 low- and 5 high-temperature grades could be specified, binder availability and regional pavement distress were used to develop guidelines for statewide PG usage. Three binders were recommended for use in the western, northeastern and southeastern regions of the state as follows: PG 58-22; PG 58-34; and PG 64-28, respectively. Validation of the binder specification with respect to low temperature cracking was accomplished using binder and field performance data from 28 projects. The results were very encouraging: the original SHRP algorithm for binder selection correctly "predicted" field performance in 22 of 28 cases, whereas the LTPP algorithm for binder selection correctly "predicted" field performance in 26 of 28 cases.Additionally, a laboratory experiment using the Superpave Shear Test (SST) apparatus was undertaken to test the effectiveness of binder "bumping," i.e., increasing the high temperature grade because of exceptionally high traffic volume and/or slow or standing traffic. The data clearly indicate that the SST is an effective tool for discriminating between binders and that 'bumping" may be effective in reducing pavement rutting. Permanent shear strain for specimens made with a PB 70-xx binder was only 25 to 33% of the shear strain for specimens made with a PG 58-xx binder.As originally configured, the Superpave mix design matrix included seven traffic levels and four temperature regimes for 28 possible compaction levels. Recognizing that the 28 compaction levels made for a somewhat unwieldy system, WSDOT attempted to reduce the number of compaction levels by conducting a series of mix designs at each compaction level. The results of the limited experiment suggest that it might be possible to limit the number of compaction levels required for mix design. Research by Brown et. al. (NCHRP 99) tends to confirm this as they have suggested reducing the number of compaction levels and provided more definitive guidance with respect to each level.Since 1993 WSDOT has place 44 projects which include some component of the Superp ave technology. For 17 of these projects parallel Hveem and Superpave mix designs were conducted. In 13 of the 17 cases, the Superpave design asphalt content was equal to or greater than the Hveem design asphalt content, though the difference was usually no more than 0.2%. A fundamental difference between Hveem and Superpave mix design methods is the compaction device. Data from these field projects indicate that the current kneading and gyratory compaction protocols (at least for 109 gyrations) yield similar air void contents.As noted previously, Washington DOT has placed 44 projects which involve some component of the Superpave technology. For 18 of the projects a conventional Hveem mix design was conducted using a PG binder (Hveem-PG). The remaining 26 projects were truly Superpave, i.e., the materials selection and mix design were established in accordance with the Asphalt Institute's SP2, Superpave Level 1 Mix Design. According to WSDOT practice the following numerical indices trigger maintenance: Pavement Structural Condition (PSC) 10 mm; or International Roughness Index (IRI) > 500 cnVkm. Although relatively "young", the 44 projects are performing quite well. The average values of rutting, PSC, and IRI (4, 91, and 121, respectively) are all well below the "trigger" values. With respect to rutting and PSC, the performance of Hveem-PG and Superpave projects is virtually identical. However, the ride quality of the Superpave projects is a bit rougher than the Hveem-PG binder projects: IRI of 134 for the former and 103 for the latter. The higher values of IRI measured on the Superpave projects may be the result of the typically coarser aggregate gradation or differences in construction techniques.WSDOT's Superpave experience has not been without challenges. Still, its overall experience has been very encouraging. Experimentation with the revised compaction matrix, continued use of the SST, field validation of the "bumping" experiment, and long-term monitoring of field performance will provide the necessary data to allow WSDOTs critical assessment of Superpave's technical merit and economic viability.

Authors:
Leahy,R. B., Briggs,R. N.

Keywords:
SHRP, Superpave, asphalt, intermodal, transportation, transportation efficiency, highway, research, program, performance, concrete, structures, highway safety, safety, maintenance, pavement, specifications, specification, asphalt pavement, pavements, tests, design, analysis, prediction, models, Washington, WSDOT, data, temperature, cracking, LTPP, traffic, volume, compaction, materials, condition, international roughness index, roughness, index, ride quality, quality, aggregate, construction, ITS, monitoring

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Abstract:
This document is an upgraded version of Research Report WA-RD 143.2 (February 1988) and is principally the result of continuing work on the WSDOT Pavement Management System (WSPMS). Various statistical methods have been used in the WSPMS and the research team wanted to summarize some of these applications in a separate, straightforward report which may be of value to a broader group of users.

Authors:
Mahoney,J. P., Seferian,M.

Keywords:
statistics, regression, materials, pavement, models

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Abstract:
The objective of this study is to obtain a better understanding of CO concentrations immediately upwind of urban roadways, the 'local background' values, and how these concentrations depend upon the surrounding traffic and the general meteorology. Measurements were made at seven sites during the winter of 1993. Local background CO concentrations were characterized by an absence of short term fluctuations, a steady buildup during the period between 3:00 PM and 11:00PM, and a lack of spatial gradients in the eight-hour averages were observed for 'trafficked' sites versus 'urban park' sites, with mean values of 1.6 and 1.0ppm respectively. A simple regression model was developed to predict the local background CO. This regression model included distance from the roadway, average daily traffic on nearby roadways, and the frequency of low wind speeds (R2=0.74; F=170). A new CO sampler was also developed as a part of this project.

Authors:
Larson,T., Moseholm,L., Cain,C., Slater,D.

Keywords:
environmental, carbon monoxide, local background, models, air pollution, air sampling

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Abstract:
This document represents the course notes used in training WSDOT personnel on regression modeling techniques. This work was done in conjunction with the development of pavement performance equations by WSDOT personnel which were based on data in the WSDOT Pavement Management System. This study was funded by the Federal Highway Administration.

Authors:
Mahoney,J. P.

Keywords:
regression, statistics, materials, pavement, models

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Abstract:
Statewide sampling of highway runoff continued through 1980-81, and the resulting data has been aggregated with that from previous years to further investigate pollutant loadings. Results have validated the solids loading model previously proposed by Asplund (1980) for Western Washington Highways and tentatively extended the model to Eastern Washington. Loading of there pollutants can be predicted from total suspended solids loading using ratios derived from the data. These ratios may be taken as constants at any Washington State location for some pollutants or as linear functions of traffic or other contaminants. Comparison of runoff from a sulfur-extended asphalt pavement with runoff elsewhere indicates higher sulfate loads in the former case. A limited sampling program along an uncurbed highway section observed higher pollutant concentrations from these sections to curbed areas. Sampling of solids adhering to the undercarriage of automobiles produced widely varying results but suggested that vehicles traveling on rural or unpaved roads accumulate significant amounts of solids that can be released on highways. The final year of field sampling will concentrate on improving the loading models, especially for Eastern Washington application, and continuing the sulfur extended asphalt study with a functional control site experiencing the same conditions.

Authors:
Tai Wik,David Chui, Mar,B. W., Horner,R. R.

Keywords:
analysis, asphalt, asphalt pavement, Concentrations, condition, control, data, extended asphalt, highway, highway runoff, Highways, loads, model, models, pavement, pollutant loading, Pollutants, program, runoff, rural, sampling, statistical analysis, sulfur, suspended solids, traffic, Washington, Washington state

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Abstract:
A highway storm water runoff pollutant loading. model has been developed based on results from con3posire sampling of approximately 600 storms at nine locations in the State of Washington over five years. The model expresses total suspended solids (TSS) loading in proportion to the product of highway segment length, average runoff coefficient, and vehicles traveling during storm periods. It was dem-onstrated that loadings of contaminants such as chemical oxygen demand, nutrients and trace metals could be estimated from TSS loadings using ratios derived from the data, The model described was developed and validated for assessing total loadings over a time span encompassing a number of storms (monthly or annually). To predict pollutant concentrations and loadings in runoff from a given storm, cumulative distributions were plotted and analyzed to determine the probability of exceeding specific concentration and loading values in a given case. Bioassay studies using highway runoff indicated toxicity to aquatic life when elevated metals deposition from high traffic volumes (in excess of 10,000 -20,000 vehicles per day) or high metals concentrations in rainfall caused runoff concentrations to exceed lethal levels. Draining highway runoff through grass channels 60 meters in length greatly reduced TSS and metals concentrations and the consequent toxic effects. The major product of this research is a guide to assessing and mitigating the impacts of highway runoff to receiving waters.

Authors:
Mar,B. W., Horner,R. R., Spyridakis,D. E., Welch,E. B.

Keywords:
Assessment, Channel, Chemical, Concentrations, data, demand, deposition, developed, highway, highway runoff, impact, impacts, Loadings, Highway runoff, metals, mitigation, model, models, pollutant loading, Pollutants, quality, rainfall, research, runoff, sampling, span, stormwater, suspended solids, Toxicity, traffic, traffic volumes, volume, Washington, Washington state, water quality

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Abstract:
A total of 241 storm events were sampled at ten sites during the first full year of statewide monitoring of highway runoff. Analyses of these data indicates that more than half of the observed solids in this runoff is traced to sanding operations. The total solids loading at each side-was correlated with traffic during the storm. The ratio of other pollutants to solids was linear when there was sufficient traffic-generated pollutants to saturate the available solids.

Authors:
Asplund,Randy L., Ferguson,John F., Mar,B. W.

Keywords:
data, highway, highway runoff, models, monitoring, Pollutants, runoff, traffic, Washington, Washington state, Water Pollutants, Washington State Monitoring

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Abstract:
At the request of the Washington State Department of Highways a study was conducted to evaluate three computer models specifically designed to predict carbon monoxide concentration at receptor points along roadways. The models were evaluated on their ability to predict values obtained from a monitoring network established along various roadways in the State of Washington. Monitoring consisted of 12 ground level CO stations, meteorological stations and traffic counters. Traffic speeds were sampled for conformity during peak hours. The final selected models, CALINE and EPA's HIWAY were given calibration factors to be used when calculating Receptor Concentrations for Impact Assessments.

Authors:
Badgley,Franklin, Rossana,T. August, Alsid,Hal F., Lutrick,David

Keywords:
air pollution, air quality, Assessment, calibration, carbon monoxide, computer, Computer Modelin, Concentrations, highway, Highways, impact, model, models, monitoring, quality, roadway, speed, traffic, Transportation Pollution Source, Washington, Washington state

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Abstract:
Federal and State laws require highway departments to prepare statements assessing the impact that proposed highway improvements or construction may have on the environment. An important consideration in the preparation of an impact statement is the anticipated effect the proposed activity will have on air quality since highway transportation is a source of several major air pollutants: particulate matter, nitrogen oxides, carbon monoxide, hydrocarbons, and photochemical oxidants which are formed in the atmosphere in the presence of sunlight. Comprehensive physical studies to predict the air quality impact at proposed sites are generally prohibitive due to the time required to obtain suitable data, the cost of such studies and the number of impact statements that must be considered by most highway departments.Methods have been developed to predict the air quality impact of new highway construction through the use of mathematical atmospheric diffusion models. Once they are properly calibrated these models can be used to test alternative locations and designs. Basically models use meteorological conditions and emission rates to predict downwind concentrations as illustrated in Figure 1.The principal objective of this research project has been to conduct a search of the literature to identify state-of-the-art air quality predictive schemes applicable to motor vehicle transportation. The available models have been analyzed in detail and evaluated in terms of selected characteristics that serve to describe the predictive capabilities of each. Limitations in the models have also been noted where appropriate.Section 2.0 o f this report describes the methods used in conducting the research. Sections 3.0 and 4.0 present the models analyzed and a general discussion of applicability, in both narrative and tabular form. Section 5.0 summarizes the study and presents the recommendations for future consideration.

Authors:
Rossano,A. T., Lamb,Donna V., Badgley,Franklin

Keywords:
air quality, Alternative, carbon monoxide, Concentrations, condition, construction, cost, data, design, environment, highway, highway construction, Highways, hydrocarbons, impact, model, modeling, models, nitrogen, particulate matter, Pollutants, quality, research, state-of-the-art, transportation, Washington, Washington state

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