Exploring Traffic End-of-Queue in a Temporal Spatial Diagram and Applications for Work Zone Safety Analysis

Vehicle queue presence and the location of the end-of-queue as a result of work zones and incidents is important for traffic management and can be acquired from inspecting each vehicle’s actual trajectory in a time-space diagram. Since tracking individual vehicle’s trajectories continuously requires a significant effort in data collection and processing, especially for a work zone with high traffic demand, this study applies speed contour maps generated from analyzing detector data around a work zone site to examine traffic at a macroscopic level and obtain queue information. Analysis techniques for identifying queue observation space (QOS) and work zone impact time on speed contour maps are proposed and assessed. Moreover, instead of counting collision events to evaluate work zone safety, an index considering end-of-queue and prevailing traffic conditions was presented. This safety surrogate is advantageous to be able to assess the safety of work zones during the planning phase, rather than after-the-fact, based on crash data. Applications of the proposed techniques on speed contour maps from a solid experimental simulation design revealed beneficial results related to QOS, average shockwave speed and safety impacts when work zones were scheduled at various times of the day with prevailing traffic conditions for freeway management.