Development of Guidelines for Work Zone Diversion Rate and Capacity Reduction

Project summary:

This project developed a comprehensive guideline to estimate the traffic diversion rates and capacity reduction for work zones. The analysis of the traffic diversion patterns with data from past work zones in the metro freeway network in Minnesota resulted in a set of diversion-estimation models that relate the diversion rates at freeway ramps with the travel times and speed levels on a freeway and alternative routes during construction. The interrelationship between diversion and work-zone traffic conditions has led to the development of an iterative process, in which a freeway simulation model interacts with the diversion-estimation models until a convergence is achieved between diversion and resulting freeway delays. Freeval was adopted in this research as the simulation tool for freeways. The test results of the iterative process with the work zone data showed promise in determining both the diversion rates and freeway delay for a given work zone. Because of the types of work zones used in developing the diversion models, the iterative process developed in this project can be applicable to only two-to-one lane reduction cases in estimating the diversion rates for the mainline exit flows, while the diversion rates at entrance ramps can be determined without such restrictions. The capacity analysis of the lane-closure sections performed in this study has also resulted in a set of suggested capacity values for the work zones with two-to-one lane reduction.

• OST-R summary report for this project (PDF)