Development of Speed-Flow Curves for Highway Work Zones with Speed Limit of 45 mph and 55 mph

摘要

This paper develops speed-flow curves for highway work zones with speed limit of 45 mph and55 mph. Out of ten data sets, the research team could obtain two data sets with congestedconditions and eight data sets with free flow conditions to establish the curves for ideal and non-ideal work zone conditions. Ideal conditions refer to a work zone with ideal geometriccharacteristics and no other speed reducing factors such as work activity and police presence.The non-ideal speed-flow curves for speed limit of 45 mph and 55 mph are respectivelyassociated with police presence and speed monitoring display in the work zones.It turned out that the shape of the 45-mph curves is different than that of the 55-mphcurves. Especially, regression analysis of the eight free flow data sets (three with speed limit of45 mph and five with speed limit of 55 mph) showed that the slope of the free flow lines issignificant for speed limit of 45 mph. On the other hand, a horizontal line can be considered forspeed limit of 55 mph since most of the slopes are statistically insignificant.In addition, the paper develops a methodology to estimate capacity and operating speed.The methodology considers the effect of non-ideal conditions as reductions in free flow speedand establishes a curve based on the reduced free flow speed. To establish the curve, one can usethe look-up tables provided in this study without going through the curve fitting process. Anexample problem was solved to show how to use the look-up tables.