טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentElias Zoher
SubjectAn Investigation of the Relationships between Travel Speed,
Road Characteristics and Traffic Accidents
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Shlomo Bekhor
Professor Shalom Hakkert
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract





The study deals with the examination of two main issues; the impact of infrastructure characteristics on travel speed, and the effect of infrastructure characteristics and speed on road accidents, taking into account roads that pass through both urban and rural areas. Therefore, the main question that this research is trying to answer is- how to create roads which serve traffic that passes through populated urban areas while simultaneously serving the local traffic and maintaining road safety. Accordingly, the study’s methodology attempts to address the problem through two approaches, an aggregate and a dis-aggregated approach.

Using the aggregate approach, a geographic information system (GIS) was used to enable extensive spatial monitoring of parameters and data related to road safety, in particular: speed, infrastructure and road accident data. The research is based on advanced technologies for collecting speed data that can be combined with road accident data. This cross-sectional analysis allows for an extensive investigation of the links between speed and road accidents and thus provides tools for broad and comprehensive speed management .

Using a dis-aggregated approach, the study focused on a specific type of road which runs through both urban and interurban areas. The main goal in selecting these types of roads is to examine the safety and mobility implications of highways which are highly ranked in the hierarchical ranking of non-roads but simultaneously run through populated areas.

The idea of investigating the data in different ways stems from discussions mentioned in the literature. On the one hand, an aggregate analysis makes it possible to draw conclusions for large areas. However, the dis-aggregated approach allows for a more focused analysis, with detailed variables that may better explain travel speed and traffic accident prediction.

The speed measures tested in this study are "speed excess" which was defined as the difference between the 85th percentile of travel speeds and the speed limit (which also expresses the difference between operating and target speed in the segment), and “average speed”. The rate of road accidents per unit distance traveled was chosen as a safety measure for the road segments, calculated as the total number of accidents observed in the segment during a specific time period, divided by the length and traffic volume in the segment.

It can be concluded from the research findings, that some infrastructure characteristics have a significant connection with travel speeds and road safety. During the planning stages of urban and interurban roads, a high uniformity of the design elements should be sought in order to create homogenous roads. This will enable continuous travel with low variability, which can contribute to reducing the number of traffic accidents, and especially severe accidents.

Furthermore, a policy should be adopted that will reduce the number of regional and main roads that cross urban areas so as to reduce the conflict between passing and local traffic. Highways and regional roads which cross urban areas must be adapted to the needs of local traffic. Therefore, on these sections, design elements that are appropriate for interurban roads should be avoided.