"Travel time reliability can be defined as consistency of travel time over time. The primary goal of SHRP 2 Reliability research is to improve the reliability of highway travel times by mitigating the effects of events that cause travel times to fluctuate unpredictably. Through this research, seven sources of unreliable travel times have been identified: traffic incidents, work zones, demand fluctuations, special events, traffic control devices, weather, and inadequate base capacity.
This guide documents the research of the L02 Project, Establishing Monitoring Programs for Travel Time Reliability. It also provides further discussion of how to develop and use a travel time reliability monitoring system (TTRMS). The Guide will be useful for system operators in determining what actions they need to take to reduce the variability of travel time and enhance reliability."