Time Gaps in Work Zones Based on Follower-Leader and Under Various Temporary Traffic Control Methods

Time gaps are microscopic flow characteristics related to driver behavior, traffic safety and capacity. Knowing time gap characteristics enables monitoring of traffic flow and taking appropriate safety measures, particularly in work zones. The objective of this study is to explore how mean time gaps change based on vehicle type and traffic control treatment in single-lane work zones. For this purpose, thirteen data sets that involved over 8250 vehicle observations were collected from six Interstate work zones in various traffic control conditions.

In terms of vehicle type, trucks exhibited significantly greater mean time gaps than cars, possibly due to longer stopping distance they require compared to passenger cars. Besides, in nearly half of the data sets, the mean time gaps of trucks following cars were significantly greater than trucks following other trucks. Hence, the time gap preference of the truck drivers differed significantly based on the vehicle type of their immediate leaders. On the contrary, such driving behavior was generally not observed in the car drives.

Next, it is also essential to identify the effects of work zone traffic control treatments on time gaps. In this study, the effects of flagger and Police presence were explored. According to the results, the mean time gaps of all vehicle types increased significantly due to flagger presence. However, the mean time gaps of only cars following cars and trucks following cars increased significantly due to Police presence. So compared to Police presence, flagger presence had a more pronounced effect on spacing out vehicles, which led to a “safer” environment, but reduced number of vehicles processed.