Measuring Non Recurrent Traffic Congestion

Measuring Non-recurrent Traffic Congestion

Measuring Recurrent and Non-recurrent Traffic Congestion

The paper describes a methodology and its application to measure total, recurrent, and non-recurrent (incident related) delay on urban freeways. The methodology uses data from loop detectors and calculates the average and the probability distribution of delays. Application of the methodology to two real-life freeway corridorsone in Los Angeles and the other in the Bay Areaindicates that reliable measurement of congestion should also provide measures of uncertainty in congestion. In the two applications, incident-related delay is found to be between 13 to 30 percent of the total congestion delay during peak periods. The methodology also quantifies the congestion impacts on travel time and travel time variability.

Analytical Procedures for Determining the Impacts of Reliability Mitigation Strategies

"Reliability of transport, especially the ability to reach a destination within a certain amount of time, is a regular concern of travelers and shippers. The definition of reliability used in this research is how travel time varies over time. The variability can apply to the travel times observed over a road segment during a specific time slice (e.g., 3 to 6 p.m.) over a fairly long period of time, say a year. The variability can also pertain to the travel times of repeated trips made by a person or a truck between a given origin and destination. Agencies are increasingly aware of the issue of reliability, although the transportation industry as a whole as yet lacks a firm understanding of the causes and solutions to failures of reliability. As the agenda for the SHRP 2 research on travel time reliability took shape, it became clear a fundamental study was required to be able to talk about travel time reliability in a meaningful way"--Foreword.