Abstract
It is now well established that crash occurrences at roadway segments or intersections are associated with a large variety of factors. Safety Performance Functions (SPF) are statistical models developed to predict crash frequencies for various design variables. In Jordan, almost half of all road crashes occur at intersections, mostly in urban areas. There is a significant number of roundabouts throughout Amman which is increasing without evaluating their safety performance. To assess safety benefits of this kind of intersections, transportation professionals need the powerful statistical tool; the SPF. This study aims to develop SPFs for roundabouts in Amman. The models consider the crash frequency, traffic volume and geometric features of all the studied 20 roundabouts. The developed SPFs were statistically significant (R^2 = 0.91) .The findings of the study revealed that crash frequency has a strong relation with the AADT, roundabout entry angle-degrees, entry path radius, splitter radius, pedestrian crossing structure, inscribed diameter, central diameter, circulating width, entry width, number of circle legs. The developed SPFs are evaluated through a comparison with others from developed countries.
Highlights
Road traffic safety has become an intensively researched topic with the aim of enabling the road authorities to identify safety improvement projects more efficiently
According to statistics released by the Jordan Traffic Institute (JTI) Jordan had 685 fatal crashes in 2017 with 76% of these crashes occurring in Amman of which 35% occur at intersections (JTI 2017)
This study provides an objective and unbiased method of measuring future safety for Amman roundabouts by developing Safety Performance Functions (SPF) to predict their crash frequencies
Summary
Road traffic safety has become an intensively researched topic with the aim of enabling the road authorities to identify safety improvement projects more efficiently. According to statistics released by the Jordan Traffic Institute (JTI) Jordan had 685 fatal crashes in 2017 with 76% of these crashes occurring in Amman of which 35% occur at intersections (JTI 2017) These facts calls for the need to establish a goal of reducing traffic related fatalities and severe injuries along the Jordanian roadway network (segments or intersections). Achieving this goal requires developing statistical models, referred to as Safety Performance Functions (SPFs) which provide realistic predictions of crash frequencies as a function of traffic volume and roadway geometries over a roadway network. Roundabouts have become increasingly popular in recent years leading to an increase in research into their effectiveness and safety performance
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