世界経済・社会統計 = World development indicators

Highway Capacity Manual改訂の動向--テイラ-教授の講演より

Generalized Linear Models (2nd ed.)

Gaining a better understanding of the factors that affect the likelihood of a vehicle crash has been an area of research focus for many decades. However, in the absence of detailed driving data that would help improve the identification of cause and effect relationships with individual vehicle crashes, most researchers have addressed this problem by framing it in terms of understanding the factors that affect the frequency of crashes - the number of crashes occurring in some geographical space (usually a roadway segment or intersection) over some specified time period. This paper provides a detailed review of the key issues associated with crash-frequency data as well as the strengths and weaknesses of the various methodological approaches that researchers have used to address these problems. While the steady march of methodological innovation (including recent applications of random parameter and finite mixture models) has substantially improved our understanding of the factors that affect crash-frequencies, it is the prospect of combining evolving methodologies with far more detailed vehicle crash data that holds the greatest promise for the future.

http://ceprofs.tamu.edu/dlord/Papers/Lord-Mannering_Review.pdf

The statistical analysis of crash-frequency data: A review and assessment of methodological alternatives

Artificial intelligence research is ushering in a new era of sophisticated, mass-market transportation technology. While computers can already fly a passenger jet better than a trained human pilot, people are still faced with the dangerous yet tedious task of driving automobiles. Intelligent Transportation Systems (ITS) is the field that focuses on integrating information technology with vehicles and transportation infrastructure to make transportation safer, cheaper, and more efficient. Recent advances in ITS point to a future in which vehicles themselves handle the vast majority of the driving task. Once autonomous vehicles become popular, autonomous interactions amongst multiple vehicles will be possible. Current methods of vehicle coordination, which are all designed to work with human drivers, will be outdated. The bottleneck for roadway efficiency will no longer be the drivers, but rather the mechanism by which those drivers' actions are coordinated. While open-road driving is a well-studied and more-or-less-solved problem, urban traffic scenarios, especially intersections, are much more challenging.

We believe current methods for controlling traffic, specifically at intersections, will not be able to take advantage of the increased sensitivity and precision of autonomous vehicles as compared to human drivers. In this article, we suggest an alternative mechanism for coordinating the movement of autonomous vehicles through intersections. Drivers and intersections in this mechanism are treated as autonomous agents in a multiagent system. In this multiagent system, intersections use a new reservation-based approach built around a detailed communication protocol, which we also present. We demonstrate in simulation that our new mechanism has the potential to significantly outperform current intersection control technology--traffic lights and stop signs. Because our mechanism can emulate a traffic light or stop sign, it subsumes the most popular current methods of intersection control. This article also presents two extensions to the mechanism. The first extension allows the system to control human-driven vehicles in addition to autonomous vehicles. The second gives priority to emergency vehicles without significant cost to civilian vehicles. The mechanism, including both extensions, is implemented and tested in simulation, and we present experimental results that strongly attest to the efficacy of this approach.

/pdf/a-multiagent-approach-to-autonomous-intersection-management-ndv1gqtnse.pdf

A multiagent approach to autonomous intersection management

This paper provides guidelines and tools for quantitative evaluations by means of fuel consumption and emissions for various vertical grade design conditions. Detailed vehicle operation conditions were represented by second-by-second speed profiles generated with the truck dynamic model and nonuniform acceleration and deceleration models. The rates of fuel consumption and emissions based on vehicle-specific power and speeds were extracted by using the recently developed Motor Vehicle Emission Simulator. The generated speed profiles were matched with the extracted rates and aggregated during a trip on the grades. As a result, the design vehicle consumed more than five times the amount of fuel on a 3,000-m graded segment when the vehicle had a speed reduction of greater than 20 km/h, as opposed to the vehicle with a speed reduction of less than 10 km/h. For emissions—carbon dioxide, carbon monoxide, oxides of nitrogen, hydrocarbons, and particulate matter of 2.5 microns or less—there were up to fivefold increases on the segment. Thus, controlling a speed reduction of less than 20 km/h can minimize adverse environmental effects from vehicle movements. In addition, this study shows that environmentally conscious vertical grade design is feasible and economically beneficial throughout the life of the highway. The provided guidelines and tools can reduce uncertainty for designing environmentally conscious highways and can be used as part of the highway design process.

https://ceprofs.civil.tamu.edu/dlord/Papers/Ko_et_al_Grades_Environment.pdf

Environmental conscious highway design for vertical grades

The research described herein documents an investigation into countermeasures that can be used to provide motorists with advance notification of traffic signals or queues from those signals that are located beyond the motorists' line of sight due to a crest vertical curve. Whereas standard roadway design ensures that stopping sight distance (SSD) is provided at all locations along a roadway, there is no standard established for when decision sight distance (DSD) is needed with respect to traffic signals. A "reduced decision zone" (RDZ) was identified in the research as the location along a roadway with a vertical curve and a traffic signal beyond the curve where SSD is provided but DSD is not. Essentially, motorists within the RDZ are provided with SSD for unexpected stopping but are not provided with the added decision-making and response time that DSD might otherwise provide as they approach the vertical curve and the downstream traffic signal. Contained within this report are techniques for determining whether an RDZ exists along an existing roadway or has the potential to exist in a proposed design. It is suggested that intersections not be located within the RDZ. In cases where a traffic signal or queue from a signal is located within the RDZ for an existing roadway, guidance is provided on both the type and location of countermeasures that can be used. Results of field tests conducted using both the suggested type and location of advance warning sign countermeasures are included within this report and its appendix.

Improving safety at signalized intersections near vertical curves

In accordance with the federally mandated Highway Safety Improvement Program, every state is required to "develop and implement, on a continuous basis, a highway safety improvement program which has the overall objective of reducing the number and severity of crashes." As part of this program, the Texas Department of Transportation (DOT) uses a formula known as the Safety Improvement Index (SII) for identifying, ranking, and selecting eligible projects. The SII is used to rank projects for potential funding by giving priority to projects that have a high benefit-cost ratio. Because the SII has not been updated within the past two decades, there is a need to determine whether the current formulation should be revised or updated. The objective of this study was to evaluate the SII in its current functional form and in its usefulness to rank and prioritize projects for safety improvement. The evaluation procedure proposed in this study used sensitivity analyses to study the effects of input variables on the ...

Evaluation of Texas Department of Transportation Safety Improvement Index as a Prioritization Tool

The Government of Burkina Faso has recently been conducting important governmental and macro-economic changes, aiming at encouraging the economic growth of the country. In order to maintain this growth, the Government has put in place a transportation program to improve the efficiency and safety of the road network. This paper documents the study carried out in 2000 on the safety improvement of rural roads in Burkina Faso. The primary objectives of the study were to prepare an assessment of traffic safety problems and to propose several countermeasures to reduce the number and severity of collisions on rural roads. To accomplish these objectives, a large sample of rural roads were visited and evaluated; all accident data and important socio-economic variables were collected; and key staff members from various governmental and private agencies were interviewed. The results of the study have shown that traffic safety problems in Burkina Faso are multidimensional, involving inefficient traffic safety management and policy, inadequate road networks, untrained drivers and defective vehicles. Several traffic safety countermeasures have been proposed for immediate, short- and long-term application. The most important countermeasures consist of creating a new institutional framework with which to improve the management of traffic safety and to train the key personnel who will be responsible for implementing traffic safety countermeasures. In the short term, the proposed countermeasures are mainly related to roadway infrastructure improvements and better enforcement tools. In the long term, the proposed countermeasures include the review of current highway traffic laws, their application, the evaluation of countermeasures already in place, and the improvement of driver training.

https://ceprofs.civil.tamu.edu/dlord/Papers/CRT_Working_paper_02-06.pdf

Dominique Lord

Papers

Environmental conscious highway design for vertical grades

Improving safety at signalized intersections near vertical curves

Evaluation of Texas Department of Transportation Safety Improvement Index as a Prioritization Tool

Traffic Safety Diagnostic and Application of Countermeasures for Rural Roads in Burkina Faso

Crash-severity modeling