In this report, Texas Transportation Institute researchers identify key work zone safety and mobility performance measures that the Texas Department of Transportation (TxDOT) should target as part of a work zone monitoring program within a district, region, or across the state. Analysis methodologies and computational procedures are presented that will yield the recommended performance measures. For mobility-based measures, researchers recommend that TxDOT target the collection of queue length and travel time delay data caused by temporary lane closures, as the congestion and delays that result from those activities are the simplest to isolate and attribute to the work activities themselves. With regard to work zone safety monitoring, researchers developed procedures that aid a district or project engineer in determining which projects are most suitable for safety monitoring via a periodic review of crash statistics occurring before and during the project. Researchers developed graphs that indicate combinations of work zone length (or work zone segment length), average daily traffic, normal crash rate, and work zone phase or project direction that will most likely allow for reasonable inferences to be made regarding the relative level of safety being maintained within the project. Researchers also developed graphs to aid field or district personnel in quickly determining whether accident frequencies being experienced during a project are within, or above, tolerance limits for that type of project on that facility. (Author/publisher)
Samenvatting