OPERATIONAL AND SAFETY EFFECTIVENESS OF PASSING LANES ON TWO-LANE HIGHWAYS

Passing lanes and short four-lane sections are installed to provide increased opportunities for passing slow-moving vehicles on two-lane highways. An operational and safety evaluation of these treatments was performed by using traffic operational field data collected at 15 sites and traffic accident data for 76 sites. It was found that passing lanes decrease the percentage of vehicles platooned on two-lane highways and that the magnitude of this benefit varies with passing lane length, traffic volume, and the level of platooning upstream of the passing lanes. Passing lanes increase the rate of passing maneuvers on two-lane highways but have only a small effect on mean travel speeds. Passing lanes and short four-lane sections do not increase accident rates above the levels found on comparable untreated two-lane highways; in fact, they probably improve safety.