Improving Work Zone Capacity Models with Naturalistic Driving Study (NDS) Data (Project B2)

Orange barrels in highway construction zone as used in road maintenance and repair

As the National Highway System grows older, an increasing number of work zones have been implemented to address the growing needs of maintenance and construction. However, the reduced operating speed, narrowed lane width and shoulder clearance, and other construction activities, have not only resulted in crashes but also caused excessive delays.

Although the freeway work zone capacity methodology proposed in the latest edition of the Highway Capacity Manual (HCM) has been substantially improved over previous editions, it is still limited by the fact of the macroscopic model, which cannot account for various work zone configurations.

In order to understand how actual work zone layouts, traffic conditions, and driver behaviors affect work zone capacity, a one-year proof-of-concept study evaluated if existing Naturalistic Driving Study (NDS) work zone data collected by the second Strategic Highway Research Program (SHRP2) could be reused to develop new (or update existing) capacity and traffic flow models for work zones.

Results suggested that the capacities predicted by HCM are lower than that by NDS regression models, which implies the HCM might underestimate the work zone capacity or additional parameters (such as population factor), which should be included in HCM models. The results pertaining to headway selections by different types of drivers can also be applied to improve or calibrate work zone planning and simulation tools. More complete work zone NDS data that cover the entire work zone area should be collected to develop car-following models at work zones in the next phase.

The results, including a preliminary headway table for use in traffic simulation software, offer a unique opportunity to model actual driver behaviors negotiating different work zone configurations. Departments of Transportation (DOTs) and transportation agencies can use this information to improve the existing work zone planning and capacity analysis tools.

This STRIDE Project B2 “Evaluation of Work Zone Mobility by Utilizing Naturalistic Driving Study Data” was completed by Dr. Huaguo Hugo Zhou, Auburn University, Dr. Rod Turochy, Auburn University, and Dan Xu, Ph.D. student at Auburn University.

Learn more about the project and read the final report at