Incorporation of Travel Time Reliability into the HCM

October 2013

The objectives of SHRP 2 Project L08 are twofold. The first objective is to incorporate nonrecurring congestion impacts into the HCM procedure. The second objective is to expand the analysis horizon from a single study period (typically an AM. or PM peak period) to an extended time horizon of several weeks or months to assess the variability and the quality of service the facility provides to its users. Travel time reliability aims to quantify the variation of travel time. It is defined using the entire range of travel times for a given trip, for a selected time period (for example, the PM peak period on weekdays), and over a selected horizon (for example, a year).