This paper deals with the scheduling of trains so as to minimize train trip times while maximizing reliability of arrival times. The amount of risk of delay (RD) associated with a schedule is used as the reliability component of a constrained schedule optimization model. The paper outlines the model developed to quantify the risk of delays to individual trains, as well as to specific track segments and to the schedule as a whole. The risk model, which deals with single track operations, can be used to estimate the likely impact on reliability of arrival times, changes in train frequencies, and operating practices; track and station infrastructure investment strategies; and train technology upgrading. An application of the model to the optimization of schedules on a track corridor is described. The results obtained using the model are compared with the schedules used by train operations planning staff, in terms of overall delay and timetable reliability. The results highlight the significance of including a measure of timetable reliability, such as risk of delays, in the objective function for scheduling optimization.

This paper assumes that in an intelligent transportation system (ITS) traffic control environment, traffic control systems will be able to track vehicles individually in a traffic stream through automatic vehicle-specific identification (AVSI). As a vehicle passes an AVSI roadside reader site, it is assumed that the reader records the arrival time and type of detected vehicle. The reader sends the information received to a local microprocessor-based traffic signal controller. The controller's built-in signal control logic then uses the information to adjust traffic signal timing to reflect the present traffic stream's characteristics. Given this assumed capability, a simulation model is developed to evaluate the benefits of the use of AVSI. To make use of AVSI, a new vehicle-specific adaptive (VSA) traffic control logic is built into a simulation of an isolated intersection. Through the simulation, identifiable, measurable, and significant benefits are found from the use of AVSI in adaptive traffic signal control logic when the incorporated VSA control strategy is tested against the pretimed control system.

Investigated in this paper is the statistical precision of annual average daily traffic (AADT) estimates resulting from short period traffic counts (SPTC). A large number of automatic traffic recorder (ATR) sites located on Minnesota's highway system are studied. Effects of various factors on estimation errors are investigated. The appropriateness of volume adjustment factors is expressed in terms of assignment effectiveness, which reflects the degree of correctness with which a sample site is assigned to an ATR group. Among several other conclusions, it is found that AADT estimation errors are very sensitive to the assignment effectiveness. The study results suggest that highway agencies should put more emphasis on sample site assignments to correct ATR groups than on the duration of count, i.e., whether it be a 24-, 48-, or 72-hr traffic count. The main study findings are confirmed by analyzing ATR data from two Canadian provinces, namely, Alberta and Saskatchewan. It is believed that the material presented in this paper can be beneficial to highway agencies in the rationalization of their traffic volume counting programs.

The potential improvement in incident detection can be achieved by examining the major factors that may influence incident rates and incident detection rates. The subsections of the central I-4 corridor were grouped by geometric characteristics including horizontal alignment (straight or curved) and vertical alignment (upgrade, level, or downgrade); and also by presence of ramps (on-ramps, off-ramps, or none). It was found that subsections with off-ramps have significantly higher incident rate and incident detection rate than subsections with on-ramps or with no ramps. It was also found that upgrade subsections have significantly higher incident rate than level or downgrade subsections. However, no significant difference in incident detection rate was found between these subsections. Based on the study results and to improve performance of incident detection algorithms on I-4, the subsections were regrouped by two factors: horizontal alignment and presence of ramps.

The ability to predict the demand for rural intracounty public transportation has become increasingly important in recent years. In this study, an attempt was made to predict the future intracounty public transportation ridership demand in rural Nebraska. Existing and historical transit operating and socioeconomic and demographic data were collected for the counties and cities in Nebraska that have rural transportation services. This information was used to develop a series of equations for predicting the future ridership demand in rural areas with or without existing public transportation services. Two equations were developed for estimating the ridership demand for counties and cities that currently do not have any public transportation services. One equation for estimating ridership demand was developed for each of the counties and cities that currently have transit services. According to the ridership demand projections made in this study, it seems that the existing intracounty public transportation systems in rural Nebraska are providing sufficient services to meet the present and future demand in most rural areas.

The successful development of deterioration prediction models requires an adequate and reliable database. The task of preparing the database for developing refined deterioration models for Virginia's interstate pavements is described. At the onset, several problems challenged the modeling effort: a database containing nonhomogeneous sections unsuitable for use in model development; a user-unfriendly system incapable of efficient data manipulation; and missing and incorrect data. A computer-assisted methodology was devised to address these limitations. Following the compilation phase, the database was subjected to a three-stage screening process. This screening helped identify observation points that were likely to adversely affect the subsequent modeling stage. The problems encountered during this study suggest some desirable features that pavement management systems are recommended to possess in order to facilitate prediction model development.

This paper describes results of a full-scale load test program that was carried out on one section of rigid pavements of a newly constructed freeway in Taiwan. The pavement tested was instrumented with strain gauges and earth pressure gauges to measure the strain of the concrete pavement and the response (earth pressure) of the subgrade. The measured data were used to study the equivalent single-axle load factor (ESLF) for various single-axle and dual-axle vehicles. The values of ESLF obtained from the load tests were compared with those determined by the American Association of State Highway and Transportation Officials (AASHTO) method and the ILLISLAB code. The results obtained in this study indicated that in general, the AASHTO method yields a reliable prediction of the ESLF; in the absence of load tests, the results obtained through the ILLISLAB analysis may complement those obtained by the AASHTO method.

An experimental program was carried out to investigate the influence that a geogrid has as reinforcement for the granular base layer of a flexible pavement constructed on sand. Tests were performed using a model testing facility that allowed repeated passes of a tire across a section of pavement that was either unreinforced or reinforced with a geogrid. Measurements were taken of the surface deformations and of internal movements in the pavement and subgrade, and these were used as a means of assessing any improvement in pavement performance due to the inclusion of the geogrid. Two different mechanisms that reduced the permanent deformation of the pavement (rutting) were recognized. They were a significant reduction in the deformation of the base layer due mainly to the confinement and interlocking of the base material, and the improved load distribution on the subgrade layer that causes a reduction of subgrade deformation. Both singleand multiple-track tests were performed. It was found that in both cases, for a thin base layer, the least surface deformation was obtained with the geogrid at the center of the base layer.

Trucks transporting metal coils are known to have been involved in several serious incidents resulting in property damage as well as loss of life. Examples include the loss of two 9,072 kg (20,000 lb) coils on a flatbed trailer on I-94 in Chicago that resulted in two fatalities and $250,000 property damage, the loss of two aluminum coils from a U.S.-based motor carrier in Ontario, Canada that killed four U.S. residents in a passenger car, and the release of several 7,000 lb coils from a tractor trailer on I-190 near Buffalo, N.Y. that killed four passenger vehicle occupants. Due to a lack of consistent incident reporting, little is known about how often coil securement fails. When incidents are reported, it has been difficult to determine the causes of the securement failure. This paper details a research effort that observed steel coil securement methods and obtained data for the development of securement failure frequency statistics. Additionally, the research analytically and experimentally examines the current regulations for metal coil securement and makes recommendations for changes to the regulations.