Modeling Impacts of Access Designs on Injury Severity at Midblock Segments of Urban Multilane Highways Using Heterogeneous Choice Regression

This paper presents results of a study that developed a statistical model to evaluate impacts of six types of access design on crash injury severity at midblock segments on urban multilane highways. A heterogeneous choice model was developed in this study to identify the significant factors contributing to crash injury severity and to quantify the impacts of access design on crash injury severity at midblock segments on urban multilane highways. For model development, a total of 153 access points with different access design were selected from Florida state roads and 1830 crashes occurred in these access points for three years (2008-2010) were collected for modeling. Results of this study shows at four-leg access points, changing full median opening to directional median opening will decrease the probability of severe injury or fatality by 2.44% and that of no-capacitating injury by 8.5%. And at three-leg access points, replacing full median opening with direction median opening will not influence crash injury severity significantly. Closing median opening will decrease injury severity compared to other access designs. Other significant factors contributing to injury severity at access points were also identified as crash type, left-turn storage space on major roads, pavement surface width, outside shoulder width, median width, speed limit, AADT, high density residential area, day light condition, age of driver at-fault, and truck involvement. The results are expected to assist transportation agencies in implementing proper countermeasures to improve safety performance at midblock segments of urban multilane highways