Lane Bias Issues in Work Zone Travel Time Measurement and Reporting

Work zones are a major source of nonrecurrent congestion. Because travel time is harder to predict in nonrecurrent congestion, accurately measured real-time information on travel time in and around work zones is a critical component of traveler information systems. State departments of transportation have been seeking to provide more accurate travel time information in and around work zones. This study investigated the accuracy of technologies for the collection of work zone travel time data and identified bias in resulting travel times by comparing the data with manually collected travel times. Two technologies that provided direct measurement of travel times, Bluetooth and automatic license plate recognition, were selected for evaluation. The two systems were deployed in metropolitan Atlanta, Georgia, and the travel time data from both were compared with travel time data collected via manual license plate matching from observational data. Although the selected technologies reported reasonably accurate travel time data in free-flow conditions, their travel times were found to be significantly biased toward the slower travel times or the nearest lanes during congested traffic conditions. This paper discusses the issue of bias and presents recommendations for future implementations.