Abstract:
Bike share, e-bike share, and e-scooter systems (shared micro-mobility) are gaining popularity throughout the United States and internationally, but the optimal system design has not been determined. This study investigated motivators for and deterrents to the use of such systems in the Pacific Northwest by using a research framework from consumer behavior theory with secondary data, participant observations, in-depth interviews, and an on-line survey of users and non-users. The survey was administered in all cities in Washington, Oregon, and Idaho that have shared micro-mobility systems. Convenience and social good were found to be major motivators, but the strongest motivators reported were exercise and enjoyment. The strongest deterrents were weather, danger from automobile traffic, and insufficient bike lanes and paths. The latter two deterrents might be alleviated through continued improvements to infrastructure; however weather cannot be changed and neither can hills. Nevertheless, the survey suggested that those issues might be addressed by promoting the popular motivators of exercise and enjoyment. Once riders have become accustomed to using and enjoying the shared services in favorable conditions, they may be more likely to figure out ways to deal with weather and hills. Any promotional activities should be targeted to the “interested but concerned” segment of the four types of cyclists, as it represents the greatest potential for increased ridership, and should emphasize personal benefits more than social appearances.

Authors:
Pimentel, R.W., Lowry, M.B.

Keywords:
Shared mobility, vehicle sharing, bicycles, bicycle riders, scooters, safety, risk, interdisciplinary studies

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Abstract:
This research evaluates the safety and operational impacts of different left turn movement treatments at signalized intersections. The project (1) compares safety and operational impacts of Protected-Only Left-Turn (POLT) phase against Protected-Permissive Left-Turn (PPLT) phase with a Flashing Yellow Arrow (FYA) indication, (2) compares safety and operational impacts of doghouse display against four section vertical display for PPLT with a Flashing Yellow Arrow, (3) and identifies if time-of-day (TOD) variable left-turn control mode with FYA induces confusion among left-turning drivers. Literature shows that converting a POLT to a PPLT control mode is associated with an increase in crash rates while reducing intersection delay. Previous research recommended to select the control mode considering traffic volume, speed limit, sight distance, number of lanes, and crash history. Previous research shows that doghouse displays are associated with larger crash modification factors, more confusion among drivers, and higher delays compared to a four-section vertical display with an FYA. The results of our driver comprehension survey showed that half of the drivers who have encountered intersections with variable left turn control mode by TOD felt confused of such phasing strategy. On the other hand, the simulation-based analysis showed that changing the left turn control mode by TOD yields more efficient traffic operations and lower average delays.

Authors:
Hajbabaie, A., Sattarov, S., Mohebifard, R.

Keywords:
Safety, traffic operations, left-turn, protected, protected permissive, permissive, time of day, simulation

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Abstract:
Recent advancements in data collection capabilities have allowed transportation-related agencies to collect mountains of safety data. There is an immediate need to find out what types of safety data are being collected, what types of safety analysis can be done with the collected data, and what (other) types of safety data and analysis approaches are required to meet safety objectives. With the increased complexity of various safety data management and analysis activities, and with most transportation agencies faced with limited staff and financial resources, there is opportunity to provide the transportation workforce, which includes practitioners and academicians alike, with the resources needed to effectively understand, manage, and analyze safety data. Safety data collection, management, integration, improvement, and analysis activities are integral to developing a robust data program that leads to more informed decision making, better targeted safety investments, and overall improved safety outcomes. This project responds to the current gaps in research and identifies a methodology that will benefit all system users. The objectives included developing a comprehensive understanding of needs and priorities with regard to safety data management and analysis; developing a set of core skills and knowledge required for safety data management and analysis; providing a comprehensive set of safety data workforce development resources that can easily be accessed for use and distribution; and identifying and utilizing proven delivery pipelines to supplement program outreach efforts and activities in the safety data area.

Authors:
Chang, K., Brown, S., Chen, C., Hajbabaie, A., Perkins, R.

Keywords:
Safety, safety data, workforce development

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Abstract:
The report assesses the usefulness and effectiveness of safety and public service announcement (PSA) messages through surveys conducted in four urban areas in t he United States: Chicago, IL; Houston, TX; Orlando, FL; and Philadelphia, PA. The surveys were designed to specifically address the types of safety and PSA messages for each respective city. A total of 2 , 088 survey responses were received and analyzed . Th e report further captures findings and recommendations based on the analysis of the survey responses.

Authors:
Boyle, L., Cordahi, G., Grabenstein, K., Madi, M., Miller, E., Silberman, P.

Keywords:
Dynamic message signs, effectiveness, public service announcements, safety, usefulness, transportation management centers

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External Links: https://ops.fhwa.dot.gov/publications/fhwahop14015/index.htm

Abstract:
Two-lane rural highways in Washington State represent approximately 4,900 miles. From 1999 to 2005, 42.8% of the fatal collisions reported on state highways occurred on two-lane rural highways. WSDOT determined that the traditional high collision frequency location approach does not necessarily reflect the safety needs of two-lane rural highways. The research team first conducted a systematic review of the network and then developed a proposed decision-matrix for the selection of countermeasures on two-lane rural highways. A rate-based approach was used to show various trends across different user groups, geometric features, and contexts. It is generally accepted that the context of the two-lane rural highway would influence countermeasure choice. The project tested two contextual surrogates for the identification of particular two-ane rural highways that may exhibit safety characteristics that are different from the rest of the network. First proximity to K12 schools (in half mile increments up to 2 miles) was tested to determine whether it could assist in identifying more developed areas, such as rural town centers. It showed promise and identified areas with lower collision severity but higher collision frequency along with a higher incidence of pedestrial related collisions. Second proximity to urban boundaries (increments up to 2 miles) as means to identify transition areas showed less promise. The decision-matrix summarizes countermeasure effectiveness by collision group and also makes reference to the findings from the systematic assessment. The project also included a limited before-after study of centerline rumble strip installations (CLRS). Although results indicate some benefits and possible collision increases, caution is noted in terms of application of these findings because of small sample sizes in the analysis and the fact that roadside characteristics could not be incorporated in the evaluation process. The report recommends the development of safety performance functions that would incorporate these features. These multivariate approaches could further assist the department in the development of system-wide and corridor level approaches for two-lane rural highways.

Authors:
Van Schalkwyk, I., Washington, S.P.

Keywords:
Two-lane rural highways, safety, countermeasures

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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:
More extensive use of precast concrete components, which are fabricated off-site and then connected on-site, could allow bridges to be constructed more rapidly. The increased use of precast components in bridges also promises to increase work-zone safety and reduce environmental impacts for bridges that span waterways. This report discusses precast concrete systems that have been used for rapid bridge construction outside of Washington State and evaluates whether they are suitable for use within Western Washington. The report also identifies key features that are important for successful precast concrete system applications. Information on previously used systems was gathered through an extensive review of published literature. Washington State Department of Transportation (WSDOT) design and construction engineers, precast concrete producers, and bridge contractors were also consulted to obtain their input on the positive and negative aspects of applied systems. Most applications have been used in areas of low seismic potential. By contrast, Western Washington is subject to strong earthquakes. Because precast systems contain connections, and connections are typically vulnerable to seismic loading, a qualitative evaluation of the expected seismic performance of each system was deemed necessary. The researchers identified four types of precast concrete superstructure systems: full-depth precast concrete panels, partial-depth precast concrete panels, prestressed concrete multibeam superstructures, and preconstructed composite units. The four systems appear to have acceptable seismic behavior, but there are concerns associated with constructability and durability. Precast concrete substructure systems have received much less attention than have superstructure systems. The use of precast substructure components can provide significant time savings by eliminating the time needed to erect formwork, fix steel, and cure concrete in the substructure. The success of the system depends strongly on the connections, which must hae good seismic resistance, have tolerances that allow easy assembly, and be suitable for rapid construction.

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

Keywords:
bridge, bridges, concrete, construction, multibeam superstructures, precast concrete, precast substructures, prestressed concrete, Rapid construction, state-of-the-art, systems, safety, environmental, environmental impact, impacts, span, Washington, Washington state, applications, transportation, WSDOT, design, seismic, earthquake, seismic loading, evaluation, performance, superstructure, prestressed, seismic behavior, constructability, durability, steel, resistance

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/594.1.pdf http://wsdot.wa.gov/Research/Reports/500/594.1.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:
Studded tires have generated much controversy over the years; a number of states have banned them, while others, including Washington, have restricted their use and passed legislation to require lighter-weight studs. This report reviews recent studies that have addressed the performance and safety of the current generation of studded tires as well as the new "studless" winter tires on late-model vehicles. The well-documented correlation between studded tires and pavement wear was not the focus of this work.The issues surrounding studded tire performance and safety are complex. From the standpoint of traction alone, studded tires, when new, often provide some benefit over the other tire types on ice-covered roads when the temperature is near f reezing. However, the advent of the new studless tires has diminished the marginal benefit, and recent studies suggest that the infrequent, narrow range of conditions necessry for benefit from studded tires may not outweigh their detrimental effect on tracton in dry or wet conditions on certain pavement types. In addition, a host of primary and secondary safety factors are related to studded tire use, many of which are very difficult to quantify, including facets of driver behavior and safety perception.

Authors:
Scheibe,R. R.

Keywords:
studded tire, traction, performance, safety, winter, research, Kirkland

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/551.1.pdf http://wsdot.wa.gov/Research/Reports/500/551.1.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:
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:
The Seattle Wide-area Information for Travelers (SWIFT) Operational Test was intended to evaluate the performance of a large-scale, urban Advanced Traveler Information System (ATIS) deployment in the Seattle area. With the majority the SWIFT system completed by June 30,1996, the SWIFT Field Operational Test (FOT) evaluation was conducted from July 1, 1996, through September 20, 1997. The unique features of the SWIFT ATIS included the provision of information for multiple transportation modes, the delivery of this information using three different devices, and the use of FM sideband as the primary communications medium. This report details the findings for the SWIFT Consumer Acceptance Study based on the evaluation objectives that were identified in the SWIFT Evaluation Plan (1995). The primary objectives of the SWIFT Consumer Acceptance Study were to assess the following: Importance of traveler information in travel planning, Usefulness of SWIFT traveler information in travel planning, Minimum set of user services and device features required to provide viable product and services, User perceptions of SWIFT device usefulness, Willingness-to-pay for different services. User perceptions of changes in travel convenience and efficiency, User perceptions of changes in traffic congestion, air quality, energy consumption, and safety. ,

Authors:
Trombly, J., Wetherby, B., Dixson, A.

Keywords:
Acceptance, air quality, analysis, Assessment, ATIS, availability, bus, computer, congestion, congestion information, Consumer, data, data collection, Energy, environmental, evaluation, group, impact, impacts, improvement, incident, interviews, Miscellaneous Library, objectives, performance, planning, portable computer, quality, reliability, safety, seattle, Study, SWIFT, System, systems, traffic, traffic congestion, transit, transportation, travel, traveler information, urban

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Abstract:
The impacts that would result from providing "reserved capacity" for trucks rather than restricting trucks are considered in this study. In the extreme case, trucks would be allowed to travel in a dedicated or exclusive lane. A more moderate approach would be to provide a cooperative dedicated lane in which vehicles such as trucks and buses could share a common lane and yet be separated from general traffic.The study determined the following. Reserved-capacity strategies for trucks would offer (1) nearly $10 million in annual travel time savings for the trucking industry, (2) a savings of about 2.5 minutes per average truck trip (less than 8 percent savings in trip travel time), and (3) almost $30 million in annual travel time savings for single-occupancy vehicles in the Seattle region. The difference in travel times between the reserved-capacity strategy that would add trucks to the existing HOV lanes and the one that would add an exclusive truck lane would be insignificant, providing little justification for the construction of an exclusive truck lane. In all likelihood, the impact of reserved-capacity strategies on safety would be small, depending on the particular reserved capacity strategy. Reserved capacity strategies for trucks would accelerate pavement deterioration in the reserved lanes, but the reduction in the pavement deterioration rates of the general purpose lanes might help to balance future reconstruction costs. Surveys of the general public and subsequent statistical analysis showed considerable resistance to reserved-capacity strategies for trucks. However, this resistance is not unlike that encountered when HOV lanes were first considered.It is the recommendation of this study that the idea of reserved-capacity strategies for trucks continue to be presented to the trucking industry, to the public, and to other impacted agencies for discussion and consideration. The study showed that the adverse impacts of such strategies are easily manageable and there is at least potential for freight-productivity improvements.

Authors:
Trowbridge,A., Nam,D., Mannering,F. L., Carson,J.

Keywords:
agencies, analysis, Annual, buses, construction, corridors, cost, costs, deterioration, exclusive truck lanes, freight, freight mobility, HOV, HOV lanes, impact, impacts, improvement, lanes, pavement, public, reconstruction, research, resistance, safety, seattle, statistical analysis, survey, Surveys, travel, travel time, travel times, truck, trucking, trucks, urban

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Abstract:
Poisson and negative binomial regression techniques were used as a means to predict accidents on the basis of highway geometrics and traffic related factors. For a particular highway section the overall number of accidents was predicted using both Poisson and negative binomial distributions. The predictions were then compared with actual accident statistics. Both methods use a log-linear function to ensure that accident prediction is always non-negative. The primary data sources were the Washington State Department of Transportation\'s Transportation Information and Planning Support database for geometric and traffic information and the Washington State Patrol\'s accident database for accident information. The maximum likelihood method was used to estimate the model coefficients. The results suggested that horizontal curvature, daily traffic, speed, number of lanes, and tangent length between curves are significantly correlated with accident occurrence. The results indicated that if accident data are dispersed relative to the mean, negative binomial regression is the most appropriate method of analysis.

Authors:
Milton, J.C., Mannering, F.L.

Keywords:
Vehicle accidents, geometric design, safety, safety management systems, research

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Abstract:
This report connects the barriers to encouraging utilitarian bicycling with the funding opportunities afforded by the Intermodal Surface Transportation Efficiency Act (ISTEA). Chapter One presents findings of the barriers to bicycling as outlined by three case studies. Safety hazards are discussed in detail. Chapter Two presents new data regarding bicycle safety concerns from Puget Sound area employees and recommends facility design improvements. Chapter Three supplements the National Bicycling and Walking Study by describing the parts of ISTEA that most pertain to bicycles. Finally, new primary data are presented as to how metropolitan planning organizations are allocating some of their ISTEA funds for bicycle projects.

Authors:
MacLachlan, S., Rutherford, G.S., Ishimaru, J.M.

Keywords:
Bicycle, non-motorized transportation, barriers, safety, ISTEA

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Abstract:
This final report demonstrates the feasibility of employing high molecular weight/high density polyethylene cylinders as the energy dissipating medium in highway safety appurtenances. It is shown that this polymer can dissipate large amounts of kinetic energy, undergo large deformations and strains without fracturing, and essentially restore itself to its original size, shape, and energy dissipation potential when the forcing function is removed.This research involves a quasi-static and impact loading experimentalinvestigation to determine the energy dissipation characteristics of HMW HDPEtubes as functions of temperature, radius to wall thickness ratio, strain,strain-rate, deformation, and repeated and cyclic loading. The results ofthis experimental program are analyzed to develop analytic energy dissipationexpressions which are then employed in the design of truck mountedattenuators (TMA), Finally, an expert system computer program, CADS, ismodified to use HMW HDPE tubes in the generalized design of crash cushions.The potential financial, legal, and safety payoffs for highway operationsassociated with developing highway safety devices which are essentiallymaintenance free are significant. Maintenance costs associated with therepair of impacted safety devices would be greatly reduced or eliminated.Tort liability exposure related to damaged or collapsed hardware would besignificantly decreased. Finally, the safety of the motoring public and themaintenance personnel involved in maintaining and repairing damaged hardwarewould be enhanced.

Authors:
Carney III, J.F.

Keywords:
Computer, computer program, cost, costs, cyclic loading, density, design, development, Energy, experimental, expert system, exposure, highway, highway safety, impact, impact attenuation devices, ITS, maintenance, maintenance free, polyethylene, polymer, program, public, research, reusable, safety, self-restoration, strains, temperature, truck

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Abstract:
The current design practice used by WSDOT for the design of permanent tieback walls is to assume that the static design of a tieback wall retaining clayey soils provides an adequate reserve of strength to prevent failure during seismic loading. This design procedure is based largely on the assumption that the soil and the wall move together ground shaking and that significant loads are not produced. For tieback walls retaining sandy soils, it is assumed that dynamic loads are produced. Mononobe-Okabe dynamic soil pressures are added to the design pressure to account for the dynamic load. The validity of these assumptions and the resultant design practices is evaluated in this study. A pilot numerical study was conducted on a forty foot high wall with three levels of tiebacks using the program FLUSH. It was found that the wall and the soil tend to move in-phase and only negligible dynamic tie forces are generated. However, the soil above and below the excavation level tends to move out-of-phase, leading to significant dynamic pressures and bending moments in the wall and near the excavation level. It appears that in least some cases, tieback walls with an adequate static safety factor may suffer significant damage or fail during seismic loading and that the use of Mononobe-Okabe dynamic pressures may be conservative.

Authors:
Fragaszy, R.J., Denby, G., Higgins, J.D., Ali, N,

Keywords:
Account, bending, damage, design, earthquake, forces, loads, pressure, program, retaining wall, retaining walls, safety, Sandy soils, seismic, seismic loading, seismic response, soil, soil pressure, strength, Tieback Walls, tiebacks, walls, WSDOT

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Abstract:
Over the last ten years passenger cars have become smaller, and the percentage of smaller cars has increased dramatically, while trucks have become heavier and longer. Median barriers, like most other roadside hardware, were developed and installed before these changes in traffic composition started. There is growing concern, supported by accident studies and preliminary crash tests, that current median barriers may provide to be inadequate and that these factors may lead to higher severity of roadside collision, injuries and fatalities. This report makes recommendations based on an extensive literature review.

Authors:
Khisty, C.J.

Keywords:
Median barriers, heavy vehicles, Self-restoring traffic barrier, safety, accidents, criteria

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Abstract:
This small car accident study investigated accidents in Washington State in four passenger car categories: subcompact, compact intermediate, and large. The primary purpose of the study was to evaluate the effects on safety of increases in the number of smaller cars on the highways. Traffic accident data for the period 1973-79 were analyzed to determine the accident severity for the different automobile classes, and this analysis showed that the smaller vehicles had a higher proportion of fatal and injury accidents that the other categories.The, accident data for 1980 were used to compare accident experience with regard to injury class of the occupants, roadway surface conditions, roadway character, light conditions, collision type, objects struck, and location of accident. Analysis showed that for total accidents per one thousand registered vehicles, the large cars had a higher rate (68) than either the subcompacts (43), compacts (45), or intermediate size vehicles (46). However, the subcompacts and compacts had higher percentages of fatalities and serious injuries to their occupants, and a higher proportion of such accidents occurred on wet, snowy, and icy surfaces. In addition, the smaller passenger vehicles had a higher incidence of overturning and rear-end accidents. The analysis suggests there will be significant increases in fatal and injury accidents in future years as the number of smaller vehicles increases. Thus, the report contains recommendations for changes in highway and vehicle design that will modify these adverse trends and reduce injuries and fatalities among drivers and passengers.Some of the recommendations can be implemented fairly quickly, but others will take longer. However, until changes are made, the accident severity for small cars will continue at a level above that for larger automobiles.

Authors:


Keywords:
Accident severity, accidents, analysis, collision, condition, data, design, highway, Highways, light, overturning, roadway, safety, Study, traffic, traffic accident data, Washington, Washington state

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