This paper examines the effects of dynamic user-equilibrium (DUE) traffic assignment with scheduled trip arrival times on network design outcomes in comparison to outcomes with steady-state travel demands. The objective is to minimize systemwide travel cost by considering alternative link improvements to an existing network (e.g., select among budget-constrained subsets of link-improvement candidates). DUE is a temporal generalization of static user-equilibrium (SUE) assignment with additional constraints to insure temporally continuous trip paths and first-in first-out (FIFO) trip ordering between all origin-destination pairs. Previous research has not investigated the effects of dynamic travel demands and schedule delay (i.e., shifts by trips to earlier or later arrival times) on network design with multiple trip origins and destinations. DUE is formulated as a bilevel program of two subproblems solved successively by an iterative algorithm that consistently converges to solutions that closely satisfy the necessary optimality conditions of this problem. Examples show the impacts of alternative combinations of network changes affecting capacities and/or free-flow travel times (e.g., ramp metering or road widening) to depend on temporal travel demands and schedule delay distributions.

Five optimization models are constructed for selecting an optimal subset of projects submitted for a statewide programming process. Our approach develops models that are consistent with user needs and appropriate for the assumptions used in the project prioritization process. Each of the models builds on a basic linear-programming formulation in which a maximization of benefits and minimization of costs is desired. The five models include the following: a priority index that provides a ranking of projects but does not directly facilitate trade-offs between project costs and the ranks (model 1); a model that incorporates a formal approach to making trade-offs between rank and cost (model 2); a model that explicitly includes policy objectives by setting a fixed goal for each objective (model 3); a model that includes a strict budget constraint in addition to requiring that funded projects equal or exceed a fixed goal for each policy objective (model 4); and finally, a model that combines the relative rankings and a budgetary constraint (model 5). Models 2–5 are developed in both a continuous and integer variable format, thus generating nine optimization approaches. Models 4 and 5 also introduce a method for determining the improvement in the overall transportation-system performance, given the current budget and decision-maker objectives.

It is unlikely that roadway construction or vehicle automation will be able to alleviate most major urban congestion in the near future (5–15 years). What else can be done to reasonably reduce congestion? Several approaches to reducing congestion by capacity allocation are reviewed: laissez-faire allocation, allocation by passenger load, ramp metering, road and parking pricing, allocation by trip purpose, rationing, and mixed strategies. These approaches are qualitatively compared against four criteria: effectiveness at reducing congestion, economic efficiency, income distribution effects, and flexibility of access for urgent trips. Recommendations are made regarding capacity-allocation measures with potential to reduce congestion and to increase economic efficiency. The equity impacts of these measures are identified and methods for mitigating these effects are proposed. Congestion pricing, together with free but metered on-ramps at freeways for nonpayers or with subsidies for lower-income households all are found to deserve further study and an incremental method of adoption is outlined.

A methodology is proposed and simple models are developed that estimate on a macrolevel the traffic volume distribution in highways lanes. The testing of the methodology and the models' calibration were done for different hourly volumes with data collected from highways in the Greater Athens area in Greece. The transferability and predictability of the models were shown by applying them to different highway traffic conditions. Thus, a useful, simple tool for traffic management is developed for usage by transportation planners and highway engineers: based on a macrolevel utilization of each traffic lane by the vehicles, the pavement maintenance can be scheduled accordingly, and better design of intersections could be accomplished by taking into account the traffic volume estimated to use each lane, especially the right one.

The present paper describes the planning and preliminary design of passing lanes in difficult terrain in Southern California and is based on an investigation of approximately 560 km (350 mi) of two-lane highways in Imperial, San Diego, and Riverside counties. The need for passing opportunities has arisen for several reasons, the most important being the fact that long sections of highways are marked as no passing zones, which leads to extensive delays, driver frustration, and increased accidents. The planning techniques described herein include the use of video-logs to create a computer file documenting existing highway conditions and a two-lane highway simulation model. The TRARR (traffic on rural roads) simulation model was used to determine the impact of proposed passing lanes and turnouts on level of service. The use of the simulation model allowed the evaluation of a range of passing lane alternatives (including length and location) for a wide range of traffic, vehicle, and driver characteristics. In total, 117 new passing lanes and four turnouts were recommended for the 560 km (350 mi) of State routes that were evaluated.

This paper presents a mathematical model for computing the path of any one point on a wheeled vehicle, which may be a bus, an articulated truck, or a wheeled robot, and the steering angle necessary for a reference point to travel a specified curve. This problem arises in applications that require determination of the swept space of a vehicle and in the automatic control of a mobile robot while the reference point on the vehicle moves along a specified path. The mathematical model is applicable to any dimension of a rigid vehicle or vehicle combination. It can be shown that the widely used Western Highway Institute (WHI) formula for highway design is a special case of the mathematical model presented in this paper. Based on this model, some inherent characteristics of wheeled vehicles, such as curvature, radius of instantaneous rotation of a point on the vehicle, and their relationship; and the independence of vehicle's orientation angle, steering angle, curvature, and radius of instantaneous rotation to its velocity, are also analyzed. The analytic solutions of two typical motions, circular and straight-line motions, have been developed, and the comparison of the simulation results with the existing standards has been conducted.

An experimental and analytical study was conducted to develop an effective method for determining realistic thermal-load induced stresses in concrete pavements. Temperatures throughout the concrete slabs were measured over an extended time period. Resulting critical stresses were then analytically derived following the procedure developed in this study. To verify these analytical stresses, load-induced strains and deflections were recorded at numerous locations on the test slab at various time periods, using the falling weight deflectometer as a loading device. The findings confirmed the importance and the need to account for the thermal gradient in the design and analysis of concrete pavements. The temperature data indicated that the temperature distributions were mostly nonlinear and can be represented fairly well by a quadratic equation. In addition, theoretical analysis of the induced stresses suggests the consideration of the total temperature distribution throughout the concrete slab depth rather than the temperature differential between the extreme slab fibers. Finally, the measured strains were close to the computed ones, showing the appropriateness of the analytical model used in this study.

Permanent deformation (rutting) in bituminous pavements is treated as a linear viscoelastic flow phenomenon and is calculated using the linear elastic layered pavement model VESYS, reported by Kenis in 1978, supplied with equivalent viscous material properties. After an initial compaction period, the model predicts that the permanent deformation per wheel pass is proportional to the static axle load and inversely proportional to the vehicle speed. The predicted permanent deformation field is realistic and independent of the material elasticity. To determine the viscosity of asphalt mixtures operating under a wide range of environmental conditions, a simple new theoretical method is introduced which is based on routine test data and requires only one parameter to be fitted to experimental data. Published wheel-tracking tests were used to determine this parameter. Rut depth predictions are compared with experimental data from a recent full-scale test in France. Agreement is generally good, indicating the applicability of this linear rutting model.

The method presented studies the real behavior of a buried pipes system and its interaction with the surrounding soil. A mechanical system is used to apply a nondestructive loading from the inside of the structure, allowing a parametric model of the complex soil-pipe structural behavior to be developed. The principle of the first inspection step is to apply a cyclic loading to the pipe and to measure produced displacements. Data obtained are investigated with a finite-element theoretical model, which provides the pipe's real behavior in its real state. The resulting model allows a theoretical analysis. By this analysis, we refine and explain deteriorations and stress distribution in each tested section of the network. This theoretical model can be used for installations in trench, embankment, or tunnel. In this paper, we present different assumptions and steps used to analyze the real structural behavior of buried pipes in operating conditions and the method to determine the safety factor. Upon this factor, we can distinguish areas with high risks and normal risks. This evaluation permits one to optimize investments of buried pipe rehabilitation.

A historical case study is made of the technological innovation and operating practices used by a large transit operator during the first half of this century. This survey can benefit present-day planners, engineers, and operators in that it illustrates the inherent flexibility of the rail mode and methods by which a given investment in a fixed plant and rolling stock may be maximized. It also shows historical precedent for many practices (e.g., joint operation of transit with freight and zone scheduling) that are currently being reintroduced or undergoing feasibility evaluation.