Development of Comprehensive Crash Models for Four-lane Divided Highways in Heterogeneous Traffic Condition

Traffic safety is of prime concern worldwide. Highway geometry should be designed for vehicle safety and efficiency. Several researches have been carried out to identify the factors contributing to road crashes and for finding measures to reduce the crash rate. One of the critical gaps in the management of highway safety is the lack of a reliable method for estimating the safety of an existing roadway with, widely varying road geometrics and vehicle mix. The focus of this work is mainly to quantify the relationship between geometric design characteristics and level of safety of intercity highways under heterogeneous traffic conditions. Study was carried out in a four-lane divided rural highway in Tamil Nadu, India and a relationship was established using statistical modeling technique. Crash Prediction Models (CPM) were developed by Poisson regression, Poisson-gamma and negative binomial modeling approach for three categories, namely, current (ith) segment, with preceding (i-1th)segment and with succeeding and preceding (i+1&-1th) segments. Results showed the significance of identified variables and the effect of preceding and succeeding segments on the current segment in the case of CPM. Attempts were also made to develop operating speed models for curve and tangent elements. From the developed models, the effect of contiguous element on the operating speed could be understood.