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Abstract

To improve road safety and to reduce accident costs, roadway geometries are frequently modified based on the relationship between deficient geometric elements and the recorded accidents. This remedial approach requires fatalities and injuries to occur before the needs and priorities of roadway improvements may be identified. Rather than adopt this approach, the present research took a preventive initiate in highway geometric design stage to detect, quantify and correct hazards prior to their being constructed. Highway geometric design is proposed to be performed in relation to vehicle dynamics. This is a major contribution from this research. The methodology was a reliability-based highway geometric design, similar to "limit state" design in structural engineering. It used probability of non-compliance with design criteria to identify drivers' behaviour responses to different design alternatives. This research focused on the development of a more correct representation of the driver-vehicle-roadway interaction - the Moving Coordinate System Design (MCSD) model, the establishment of an evaluation process for the safety level of an entire highway, the application of the "racing car model" as the upper operating limit, the development of VHVIS.PAC algorithm to utilize photolog data as the geometric design input for reliability analysis, and the incorporation of the growing knowledge of human factors into highway geometric design. The research applied reliability theory to geometric design for an entire highway by incorporating vehicle dynamic characteristics, operational experience, human factor consideration and the ultimate limit of road-vehicle interaction. It provides the designers with opportunities to visualize as quantitatively as possible how the design will be experienced by individual drivers under the range of speeds and other operating conditions that will occur when the highway is actually built and put into use. The resulting safety performance measures from all available design alternatives could eventually lead to a cost-effective geometric design process. The following questions are addressed by this research: • How do different groups of drivers, such as design drivers, normal drivers and expert drivers operate on the same roadway? What kind of safety performance can be expected from each group? • Is the difference in the margin of safety among different driver groups significant? • What is the cost-effectiveness associated with each modification of a particular design? • What is the connection between design and traffic operation criteria? How does every design criterion reflect the anticipated operation of the highway? How does the proposed model fit into the existing geometric design process?