Safety and Operational Effects of the Interstate 66 Active Traffic Management System

Abstract

An active traffic management (ATM) system was activated on Interstate 66 (I-66) in northern Virginia in September 2015. The ATM system included advisory variable speed limits (AVSLs), lane-use control signals (LUCS), and dynamic hard shoulder running (HSR). This paper quantifies the operational and safety effects of the ATM system on I-66 using approximately 2 years of crash and operational data following system activation. The operational analysis showed that off-peak hours experienced significant travel time improvement after the ATM system was activated, but peak periods in the peak direction of travel generally did not see improvement. Further analysis revealed that most of these improvements occurred on the HSR sections. The safety evaluation results showed 4%, 4%, and 6% reductions in total (all severity), multiple-vehicle (all severity), and rear-end (all severity) crashes, respectively, across the entire corridor. Segment-level analysis again showed that the most safety benefits were observed at locations with HSR (31%–38% crash reductions), and no significant reductions were found on the sections with only AVSLs and LUCS.