Conclusion

This case study presents a high-level, data-driven approach for measuring work zone mobility performance using NPMRDS data. The case study project team used a simple methodology without complex modeling approaches and data analysis techniques. Two different analysis tools (Excel and the R statistical analysis tool) were used to illustrate choices that agencies may make in conducting the analyses. State DOTs and other agencies can follow this simple process to measure and manage work zone mobility performance and determine when and where work zone delays occur, what causes those delays, and how those delays can be mitigated or eliminated. The NPMRDS provides a rich foundation of travel time and speed data, which can be used to measure basic travel time and speed impacts of work zones, conduct variability analyses (e.g., temporal, spatial), calculate travel time reliability metrics, and estimate delays and road-user cost impacts of work zones. NPMRDS data can also be used to model work zone queues, but this case study does not calculate queue lengths. The performance measurement data can be used to manage work zone mobility performance across all aspects including policy, process, planning, design, traffic analysis, engineering, contracting, construction, and post construction.

When combined with additional contextual information such as incident, crash, weather, and special event data, work zone performance metrics can be used to further assess cause and effect, draw correlations, and appropriately take systematic and programmatic actions to better understand and alleviate work-zone-related congestion.

Key takeaways from measuring work zone mobility performance using the NPMRDS include:

• The NPMRDS can be used for work zone mobility performance management purposes. Usable data are important to work zone performance management. With free access to the NPMRDS, transportation agencies can use these data for work zone impact analysis and performance management. The NPMRDS can be used for analysis of congestion patterns and delays, as well as travel time and its variability. Such analyses can provide critical information toward identifying the spatial and temporal patterns of work zone delays (i.e., where and when work zone delays occurred), as well as the extent of the delays (i.e., how much delay road users experienced due to work zone activities).
• Simple analysis of NPMRDS data can inform work zone impact analysis and performance management. Complex modeling approaches sometimes discourage transportation agencies from using mobility analysis tools and datasets. However, simple analysis of NPMRDS data that does not require sophisticated technical and data analysis skills has the potential to provide meaningful insight into work zone mobility impacts and performance management. Such simple analysis is practical and implementable with limited agency resources.
• Work zone mobility performance management information from the NPMRDS can be used to develop optimal traffic management strategies for work zones. Quantifying work zone mobility impacts does not necessarily address adverse mobility effects of work zones unless the analysis is coupled with developing a traffic management strategy to mitigate the impacts. Work zone mobility impact performance management using the NPMRDS can be the basis for transportation agencies to identify and implement optimal traffic management strategies for work zones (e.g., limiting road closures during selected hours of the day, providing alternate routes to road users, and delivering more targeted public information campaigns).
• Combining NPMRDS data with other data can enable richer work zone performance analysis. Combining NPMRDS data with other work-zone-specific contextual data (e.g., type of work zone activity, weather, incident, enforcement, and traffic volume) can enable a more comprehensive assessment of work zone impacts.
• The NPMRDS does have its limitations. The NPMRDS does not cover non-NHS roads, which is a limiting factor. NPMRDS roadway segment lengths can be very long, especially in rural areas, which can lead to an over generalization of performance data over a long roadway segment. NPMRDS data are not available in real-time, which rules out its applicability for real-time use cases. One way to overcome some of these limitations is to purchase more granular probe vehicle data from any of the commercial providers of such data. Different providers offer different packages, including real-time data, extended roadway coverage, and more granular road segment coverage. The NPMRDS does not provide hourly volume data, which is essential for drawing the context between congestion and traffic volume and for estimating road user costs. Agencies can either use the NPRMDS AADTs and convert them to hourly volume estimates or rely upon their own regional data to fill this gap.