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Estimating accident frequency at signalized intersections as a function of traffic congestion
Abstract
The need for an effective way to measure the effects of changes in traffic volumes and volume to capacity ratios (v/c) on accident frequency at signalized intersections was the motivation for this research. Today, different methods are incorporated by various agencies for determining accident reductions, but no widespread or uniformly accepted method has been established. Many factors are believed to influence accident frequency. Some of these factors such as traffic volume and geometric and signal designs are easily observed, documented, and controlled while other factors such as regression to the mean, varying levels of accident reporting, and human behavior are not. A new technique which compromises the effects of the uncontrollable factors and emphasizes the effects of the controllable factors was introduced and implemented in this research. Accident frequency in this new technique is also related to the conflicting movements to which the colliding vehicles belong. For a given type of accidents, data sets including observed number of accidents, traffic volumes, and v/c ratios of the conflicting movements were sorted in ascending order by the appropriate parameter and then divided into groups of equal sizes. Average number of accidents, traffic volumes, and v/c ratios of the above groups were then used to develop series of least squares regression equations to predict the number of accidents in the a.m., p.m., and off peak periods. Equations were developed for the four most frequent collision types which included rear end, left turn leaving, left turn entering, and cross traffic collisions. These equations provided fairly good estimates when they were tested using an out of sample empirical data. This research concluded that these equations can be used to help identify sites with unusually high accident frequencies and as an effective tool in evaluating benefits and costs for intersection improvements.
Subject Area
Civil engineering|Transportation
Recommended Citation
Al-Turk, Motasem Ahmad, "Estimating accident frequency at signalized intersections as a function of traffic congestion" (1995). ETD collection for University of Nebraska-Lincoln. AAI9528817.
https://digitalcommons.unl.edu/dissertations/AAI9528817