Headway Times on Urban, Multiple Lane Freeways

Abstract

Transportation departments commonly suggest following lead vehicles with headway times of two seconds or more. However, research has shown that headway times of under two seconds are common and that headway times vary across different roadway types. Here, we obtained and analyzed traffic video footage to measure headway times on four- and five- lane urban freeways in Los Angeles County. When a five second headway cutoff was applied, 58.3% of headway times were shorter than two seconds and the median headway time was 1.74 seconds. We performed a regression analysis to examine how speed, testing location, and travel lane were associated with headway times. Headway times were fairly consistent across testing locations. Speed was positively associated with headway times, and headway times were shorter in lane one compared to lanes three and four. These results demonstrate that headway times of under two seconds are ubiquitous on multiple lane, urban freeways.