A simulation study modeled the impacts of a weather-responsive traffic signal timing system in Waterloo, Canada and estimated the system can reduce total intersection delay up to 20 percent.
A journal article highlighting the results of a university research.
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Region of Waterloo:

Effects of winter weather on traffic operations and optimization of signalized intersections

Summary Information

This research focuses on measuring how traffic can affect signal related traffic parameters and exploring how to modify pre-timed signal control under adverse weather conditions.


A field study found that saturation flow rates were 17 percent and 25 percent lower on slushy and snowy road surface than on normal road surface, respectively. Also, the study showed that road surface condition had limited impacts on start-up lost time. Free flow speed is 16.9 percent lower on slushy surface than on dry surface and it is 23.3 percent lower on snowy surface than on dry surface. Using these results as inputs, the research team developed weather-specific signal plans with aid of Synchro for one uncoordinated intersection and one coordinated corridor for adverse weather conditions. Inter-green time, cycle length, green split, and offsets were adjusted accordingly.

Subsequently, these plans were evaluated using both Synchro and VISSIM. The general patterns in terms of the benefits achieved by implementing weather-specific plans found in the VISSIM results agree to those found in the Synchro results. Total network delay in one hour, which is the expected sum of delays experienced by all vehicles traveling within the network (the coordinated corridor) in one hour, was used to quantify the overall traffic performance.


  • The evaluation results show that the efficiency benefits of implementing weather-specific plans on a coordinated corridor are significant, especially for coordinated directions.
  • The magnitude of benefits is much larger compared to implementing weather-responsive plans on an uncoordinated intersection. I
  • n snowy conditions, the weather-responsive plan has the potential to decrease the total delay experienced by road users by up to 20 percent (implementing the optimal plan at medium traffic demand on snowy road surface condition).
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