Examination of the Effect of Driver Population at Freeway Reconstruction Zones

This paper presents an investigation into the effect of the driver population factor on the capacity of long-term freeway reconstruction zones. A major reconstruction project in Ontario, Canada provided an opportunity to conduct this investigation. Comprehensive data on traffic, weather and work activity were used. Three different analyses were conducted which compared mean capacity flows during different times of day and days of week to estimate the effect of the non-commuter driver population during weekdays and weekends. The study found that the effect of the driver population factor on the capacity of the reconstruction site was highly significant. Based on a factor of 1.0 for commuter traffic, a driver population factor of 0.93 was estimated for the afternoon peak period and 0.84 for weekends. Also, the driver population factor is likely responsible for a capacity reduction on weekends when compared to weekdays. This capacity reduction was 12 percent in one direction of travel and 17 percent in the other direction. Both the driver population factors and the capacity reductions on weekends found in this study are considered conservative given that these data were collected in April and early May, and that there is a higher proportion of tourist drivers during the summer season at this site. Nonetheless, the numbers are consistent with empirical observations from previous studies and provide further guidance for using the driver population factor that appears in the current HCM procedures.