California is studying the feasibility of a statewide, high-speed rail (HSR) transportation system as a link between major cities in the northern and southern portions of the state. This system will complement the state's existing transportation system and serve as an alternative to air and auto travel. In this paper, the writers provide a condensed description of the findings and conclusions drawn from the 1996 California “High Speed Rail Corridor Evaluation & Environmental Constraints Analysis,” which they prepared for California's Intercity High Speed Rail Commission to document and analyze the potential statewide HSR corridors.

The railroad test track (RTT) at the Transportation Technology Center (TTC) in Pueblo, Colo., was constructed in the early 1970s to support high-speed testing of new railroad rolling stock. Through the years it has been used to test a wide range of railroad passenger and freight cars and locomotives. Now, 20 years later, a new high-speed train set is being procured by Amtrak for service in the improved Northeast Corridor. The test facilities at Pueblo will play an important role in acceptance and safety testing of new high-speed train sets in the United States. The Federal Railroad Administration (FRA) commissioned a study to review the existing condition of the test track and to make recommendations as to possible improvement options so that the facility would be able to test current and future generations of high-speed rail equipment. This paper describes the condition of the test track and explores ways in which it may be modified to accommodate the testing of high-speed train technologies in the near future and into the next century.

Dipped track profiles between rail transit stations can significantly reduce propulsive energy, braking energy, and travel times. This work quantifies their potential benefits for circumstances reflected in various values for dips, speed and acceleration limits, station spacings, and available power. A deterministic simulation model has been developed to precisely estimate train motions and performance using basic equations for kinematics, resistance, power, and braking. For a 1% dip (i.e. a vertical dip equal to 1% of station spacing) in which gradients never exceed 4%, our results show savings (compared with level tracks) exceeding 9% for propulsive energy, 15% for braking energy, and 5% for travel time between stations.

Current analytic models for optimizing urban transit systems tend to sacrifice geographic realism and detail in order to obtain their solutions. The model presented here shows how an optimization approach can be successful without oversimplifying the spatial characteristics and demand patterns of urban areas. This model is designed to optimize a grid transit system in a heterogeneous urban environment whose demand and supply characteristics may vary arbitrarily among adjacent zones. Network characteristics (route and station locations) and operating headways are found that minimize the total cost, including supplier and user costs. Irregular many-to-many demand patterns, zonal variations in route costs, and vehicle capacity constraints are considered in a sequential optimization process.

This paper develops a system of disaggregate models that accounts for the effect of intersection, driver, and traffic characteristics on gap acceptance for left-turn maneuvers at urban T-intersections controlled by stop signs on the minor roads. The waiting time for each driver is first modeled using the hazard function. The binary probit model is then used to find the drivers' probabilities of accepting or rejecting a gap. These probabilities are used to calculate the critical gaps of individual drivers. The expected waiting time is included in the model as an explanatory variable. A multiple regression model is used for predicting the intersection mean critical gap. To estimate the parameters of the models, disaggregate data were collected by observing and interviewing drivers at 15 urban T-intersections in the Greater Amman area. The results show that the distribution of critical gaps is influenced by driver socioeconomic characteristics, expected waiting time, time of day, and trip purpose. The mean critical gap is influenced by total opposing traffic flow, number of major-approach lanes, presence of a median with a left-turn lane, maneuver type, speed of major road, and time of day. The proposed methodology can be used to calculate the critical gaps of individual drivers and, in turn, the mean critical gap at a specified intersection that is needed for delay and capacity analysis.

A new axisymmetric finite-element pavement-analysis program BIMODPAV capable of accounting for the bimodular nature of the asphalt concrete is developed. The program also considers the nonlinear behavior of the base, sub-base, and subgrade layers. The new program was verified with the existing programs within their capabilities. The effect of considering the bimodularity of asphalt concrete in the analysis is apparent at high temperatures and when it is used for thick pavements. Strains and displacements calculated using the bimodular analysis are almost always higher than the strains and displacements calculated using the single-modulus approach. When asphalt concrete is characterized as a bimodular material and its underlying layers as nonlinear materials, the displacements and strains are as much as twice the corresponding single-modular solution. Bimodular analysis of asphalt concrete causes higher tensile strains at the bottom of the asphalt layer and higher vertical strains on top of the subgrade resulting in reduced fatigue and rutting performance predictions.

The rut susceptibility of large stone mixtures (LSMs) was evaluated from laboratory materials characterization tests that included compressive creep and recovery tests on LSMs and conventional base mixtures, and repetitive simple shear tests. Results from compressive creep and recovery tests on core samples are mixed. Although there are LSMs that exhibit improved rut resistance over conventional mixtures, this was not consistent for all comparisons made. This result may be due to differences in degree of stone-on-stone contact between the LSM cores tested. Data from repetitive simple shear tests also demonstrated the potential for generating additional confining pressures due to the tendency of the mixtures to dilate. While the additional confining pressure due to dilation would tend to reduce the compliance of a mix, test results indicate that allowing too much dilation will also not be beneficial in terms of rut resistance, thus, suggesting an optimum level of dilatancy.

According to current highway design standards, horizontal and vertical alignments are treated separately in two-dimensional (2D) projections. In this paper, a model developed by the writers is used to study the effects of considering three-dimensional (3D) alignment on design requirements for sight distance. First, the paper examines the required minimum radius of a horizontal curve combined with a crest or sag vertical curve in a cut section. Also, the required minimum length of a crest vertical curve combined with a horizontal curve in a fill section is studied. The results show that the 3D design requirements may differ significantly from those in separate 2D projections. Depending on the vertical alignment and on the cut side-slope, 2D design may underestimate or overestimate the required radius. In fill sections, the 2D alignment overestimates the required length of the crest vertical curve when combined with long horizontal curves. In summary, the 2D alignment can compromise both safety and economics of highways. As a result, it is concluded that 3D-based design standards should be developed and used in highway geometric design.

A feed-forward back-propagation–type neural network was applied to airborne lead data collected around a busy highway interchange in Birmingham, England. The data were taken during the early 1970s, when lead emissions from vehicles were at their highest. The neural computation was capable of identifying realistic isopleths of lead concentrations around the interchange for summer/winter and daytime/nighttime conditions. A second neural study on blood lead levels taken from residents all over Birmingham was also undertaken. This analysis augmented the findings of the original study and highlighted the importance of age, sex, location, and age of house on residents' blood levels. It was also found that multiple linear least-squares regression analysis gave very poor results and should not be used for interpreting this type of highly nonlinear data. The neural analyses provided a relationship between airborne and blood lead concentrations, and suggested that opening the interchange had caused the blood lead levels in schoolboys, living adjacent to the highways, to increase by about 9%.

A study of interactions among crossing vehicles at an intersection forms an important attribute for evaluating the safety at urban uncontrolled intersections. In the present study, an attempt is made to develop a methodology based on probabilistic approach for determining the possible traffic conflicts at urban uncontrolled intersections. The developed model is validated using field data. The model can be used for quick estimation of possible conflicts at urban uncontrolled intersection. Issues related to the applicability of the model to identify the impact of parameters such as cross-road traffic flow and percentage of turning traffic on number of conflicts are briefly analyzed.