Assessment of the Effect of Freeway Posted Speed Limit Reduction on Vehicular Delay at a Work Zone

The reduction of posted speed limit at a freeway work zone plays an important role in ensuring safety of transportation system users and construction workers. However, it increases vehicular delay. The length of the work zone, the number of lanes closed, and the traffic volume further lower available capacity and cause disruption to the traffic flow. The effects of the reduced speed limit along with the aforementioned factors need to be quantified for better operational performance and system maintenance. This manuscript presents an evaluation of these effects at a freeway work zone using Vissim traffic simulation software. Only the delay experienced by the motorist in the queue while driving through the work zone section was considered to assess the effect on vehicular delay. Outputs from multiple Vissim simulations using different seed numbers were used to compute the average vehicular delay and the total vehicular delay, and, assist in examining the effects. The results obtained indicate that both average vehicular delay and total vehicular delay increase with the increase in speed reduction at the work zone. The queue length increases considerably for both 10 mph and 20 mph speed reduction scenarios when one lane is closed. However, for the case of two-lane closure, the queue length remains similar for both speed reduction scenarios. The average vehicular delay and total vehicular delay increase by 650 seconds and 850 hours with an additional lane closure, respectively.