Assessment of non-recurrent traffic congestion caused by freeway work zones and its statistical analysis with unobserved heterogeneity

Freeway work zones with patching, paving, lane marking, debris removing, and weeding cause temporary capacity reduction in the freeway and may lead to non-recurrent traffic congestion. Such non-recurrent traffic congestion amounts to 10% of total traffic congestion in the U.S. and 31% in Germany. Non-recurrent traffic congestion has been estimated by using the capacity and the number of closed lanes in work zones and the upstream traffic demand of work zones. However, the number of the closed lanes may be insignificant due to operational strategies such as using the shoulder area and composing additional lanes by temporarily reducing the existing lane width to mitigate traffic congestion. Therefore, the objective of this study is to develop a method to quantify non-recurrent traffic congestion caused by freeway work zones based on traffic flow data and spatio-temporal work zone information. In addition, to demonstrate the efficacy of the developed method, a case study is conducted based on one-year historical traffic data and work zone data on major freeways in Korea. Then, multivariate statistical analysis with unobserved heterogeneity is performed to describe factors of non-recurrent traffic congestion caused by work zone activities. Due to the fact that a work zone project is usually implemented according to schedule, such negative impact as non-recurrent traffic congestion is inevitably produced. Thus, the results can be practical for the performance evaluation of congestion management programs for work zone by quantifying non-recurrent traffic congestion. Additionally, the results from the statistical analysis can be potentially useful in developing a forecasting model for providing travelers with traffic information such as an alternative route to escape non-recurrent traffic congestion by freeway work zones.