Estimating Work Zone Capacity from Point Sensors: Challenges and Lessons Learned

In recent years, federal and state-level policies on work zone mobility have placed an emphasis on performance monitoring of significant freeway work zones. With new requirements for assessing work zone impacts on the traveling public, agencies face important challenges with instrumenting and evaluating work zones. Traditionally, agencies have relied on custom instrumentation or person-based monitoring of work zones, which can be very resource-intensive. In an effort to overcome the need for custom data collection in work zones, this paper explores the use to existing roadside radar sensors that are commonplace for many agencies across the US. The method uses detailed work zone diaries completed by the contractor to identify location and temporal extent of work zone activities, and uses that information to query an existing sensor database. The paper presents the approach, shows results, and discusses challenges associated with this automated data collection approach. The method is ultimately geared at estimated work zone capacities for use in the freeway facilities analysis method described in the Highway Capacity Manual 2010. The findings show some promise, but are oftentimes impacted by inadequate placement of the sensors. The paper concludes that a targeted instrumentation may in the end allow for more reliable and efficient data collection, despite the additional resource needs.