Identification of Black Spots and Urban Interchanges Safety Rating Using Analytical Hierarchy Process (AHP)

The main objective of this study was to identify the type of accidents and black spots, as well as the amount and severity of accidents at urban interchanges. Assessment of prevailing traffic crashes are based on the crashes involving 10 interchanges that has been occurred over 3 years in the state of Virginia in America. Analytical Hierarchy Process is used for ranking the safety level of the interchanges based on competent and qualified experts and data were analyzed. In analyzing the results, researches conducted in the United States using the TRIS database and studies in the field of safety in Iran for interchanges were used. The economic assessment of the costs of accidents, the figures provided by the Safety Council of America has been applied. Finally it was concluded that major share of accidents in cloverleaf interchanges are for the entrance and exit ramps and crossover region and more than 50% of accidents in partial cloverleaf and single point interchanges occur at the crossroads. Also rear end accident is the most common type of accident in interchanges and there is no significant difference between the percentages of accident occurrence. While experts and engineers express that directional interchange as the safest interchange and because it can be different ways of passing vehicles and the lack of crossovers.