Analysis of accidents is essential to figure out the actual relationship between accident causes, severity and location with factors such as road geometry, vehicle characteristics and human behaviour and features that cause accidents. Some accidents may happen due to more than one reason for the same main cause. It is known that accident data depend basically on the police reports. Reported accidents are usually below the actual number and are not oriented towards future detailed analysis. To have a good data base for accident analysis may require a relatively long time. Existing records are neither accurate nor detailed enough for the purpose of data analysis. Combined with other data sets, the traffic conflict technique is an efficient tool for analyzing traffic safety problems at specific sites. The conflicts do not only reflect the number of accidents, but also their nature. The process for a conflict to occur is almost identical to that of a compatible accident. The observations of a conflict can therefore be used as basis for explaining how these situations occur. Conflicts are classified into three and these are: potential conflicts, slight conflicts and serious conflicts (potential accident). To improve the safety of existing road system and facilities, good understanding of the relationship between accidents/conflicts and geometry of the highway and other affects is required. The objectives of this paper are to identify the roadway variables that affect traffic conflicts at uncontrolled intersections in Greater Cairo, and to develop mathematical models of conflict rates with the road variable. Alternative statistical methods of analysis based on the general linear model framework are discussed. This framework provides a flexible range of statistical models for representing response of mean conflict rates on design variables of interest and for selecting the distribution of conflict rates within individual classification cells. A special field survey was launched to collect data required for model calibration. Provision of some significant countermeasures for improving road safety levels are presented. (A) For the covering abstract of the conference see ITRD no 207828. The reprints are also available at the web - http://www.vti.se/pdf/reports/K18APart1.pdf; http://www.vti.se/pdf/reports/K18APart2.pdf and http://www.vti.se/pdf/reports/K18APart3.pdf.
Samenvatting