Assessment of Link Reliability as a Function of Congestion Components

Abstract

Travelers’ perception of reliability of a road network is typically based on factors contributing to both recurring and nonrecurring congestion. However, literature documents little research to integrate, estimate and assess congestion using both these disparate congestion components. Integrating recurring and nonrecurring congestion components to estimate congestion helps address questions such as “How reliable are roads in the transportation network?” “Which path is more reliable to reach the destination from an origin within an on-time window during a certain time of the day?” The focus of this paper is to develop and illustrate the working of a methodology to estimate travel time and its variations, travel delay index due to crashes and their severity, congestion score and reliability of each link in the network. Traffic volume, link capacity, travel speed, crashes and their severity, and estimated time taken for normal traffic conditions to restore after a crash are used in the computations. Temporal variations in travel time and crashes for each link are also studied as travel demand and crash occurrence depend on the time of the day. Sensitivity analysis is also conducted to examine and assess reliability of links based on variations in weights to integrate recurring and nonrecurring congestion components. Data collected for the city of Charlotte in Mecklenburg County, North Carolina are used to demonstrate the methodology.