Work-Zone Traffic Operation and Capacity

In assessments of the impact of expressway lane closures on traffic flow, current practice generally involves an assumption of the nominal capacity per lane which varies, in some cases significantly, by jurisdiction. Situations have been observed by the Ministry of Transportation of Ontario (MTO) where application of such a simplistic guideline, particularly in the absence of specific consideration of the effects of heavy vehicles in the traffic stream, has led to significant congestion issues and negative public reaction. Preliminary research, conducted on behalf of MTO with respect to overnight lane closures on MTO’s 400-series expressways in the GTA, suggests the existence of two operational regimes. The first regime, found where the demand is insufficient to result in queue formation at the lane closure and merging from the closed lanes is orderly, suggests a capacity in the order of 1,750 veh/h/lane, towards the higher end of the range of currently assumed values. The second regime, found where demand is such that a queue has formed, suggests a much lower capacity in the order of 1,100 to 1,300 veh/h/lane, towards the lower end of the range of currently assumed values. This research also looked at the equivalency of heavy vehicles in a work-zone, lane closure context. These results were based on relatively limited data and further data collection and analysis is recommended to verify these preliminary findings.