Safety Impacts of Auxiliary Lanes at Isolated Freeway On-Ramp Junctions

摘要

This article presents a two-part study to quantify the safety impacts of auxiliary lanes at isolated on-ramp junctions on freeways. In the first part of this study, the safety performance of on-ramp junctions with auxiliary lanes was compared with isolated on-ramp junctions without an auxiliary lane. Sixteen sites with auxiliary lanes and 19 sites without an auxiliary lane were selected in Texas. Two thousand and twenty-six crash records from 2003 to 2008 were analyzed in terms of total crash rate, crash severity, and major crash types. The results show that isolated freeway on-ramp junctions with auxiliary lanes have a significantly lower average total crash rate and average rear-end crash rate. In the second part of this study, regression models were developed to relate crash rate with influencing factors for on-ramp junctions with auxiliary lanes. The best regression model shows that the crash frequency is positively proportional to the number of lanes on the freeway and the average daily traffic per lane on the freeway, but negatively proportional to the length of the auxiliary lane and the percentage of heavy vehicles on the freeway.