Chapter 4 of the 1985 Highway Capacity Manual uses weaving and nonweaving speeds as measures of effectiveness (MOEs) to evaluate the quality of service in freeway weaving sections. However, recent research suggests that speed may not be a reliable indicator of traffic performance. Speed and conflict rates (in particular, lane change (lc) and rear-end (re) conflicts) are tested in terms of their sensitivity to geometric and flow variables. The testing environment is a microscopic simulation model developed for FHWA named INtegrated TRAnsportation Simulation (INTRAS), which has been extensively validated on freeway segments throughout the country. For simple one-sided freeway weaving sections, proposed conflict rates were found to be potentially more effective than speeds as an MOE. This finding is demonstrated by a higher sensitivity of the conflict rates moe compared with the speed moe to several geometric and flow variables at the weaving section. Lc and re conflict rates were sensitive to changes in the volume-to-capacity ratio (vc), reaching their maximum level for vc in the range 0.9 to 1.0. Lc and re conflict rates were also sensitive to changes in the volume ratio (vr), reaching their maximum level for vr in the range 0.3 to 0.5.
Abstract