Abstract:
This paper presents an investigation into the effect of darkness on freeway capacity at long-term reconstruction sites. It is part of ongoing research to examine the factors that affect freeway capacity at work zones. Capacity data from two work sites in Ontario, Canada were examined. At each site, capacity observations during the PM peak period were recorded on weekdays before and after the change from Eastern Daylight Time to Eastern Standard Time. Data from video records were then processed using 5-min intervals. Heavy vehicles were converted to passenger car equivalents using the "Highway Capacity Manual" equivalency factors. Study results suggest that darkness has a significant effect on freeway capacity at freeway reconstruction work zones. However, darkness affected capacity differently at the two sites investigated. At one site, the decline in freeway capacity due to darkness was found to be 7.5% while this decline was found to be only 3.25% at the other site. The study linked this difference to the effect of grade at the second site. This, in turn, suggests that the compound effect of two or more variables on freeway capacity at reconstruction sites is interactive rather than additive, which is consistent with findings from previous stages of this research.
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