“Hours of Congestion” as a Transportation Measure of Effectiveness Under Capacity Constrained Conditions

ITE JOURNAL / DECEMBER 1998 THE TRANSPORTATION PROFESsion needs to respond to changing needs as major metropolitan areas across the country struggle to deal with increased levels of congestion. These unprecedented congestion levels not only call for innovative, cost-effective solutions to transportation problems but also new tools to evaluate the impacts of alternative improvements. Traditional measures of effectiveness (MOEs) that were effective in evaluating transportation system performance in the past are unable to predict performance under capacity constrained conditions. This is because most of the traditional MOEs evaluate peak-hour conditions. In the past, increasing transportation supply enhanced peak-hour operations. But with phenomena like peak spreading and latent demand observed under congested conditions, peak-hour operations are often unaffected as a result of transportation supply enhancements. Improvements, however, do affect peakperiod conditions. Therefore, an evaluation process aimed at peak-period analysis proves to be more effective under capacity constrained scenarios. Modifications and revisions of traditional evaluation tools are necessary to adequately address the impacts of congestion and related phenomena. This paper discusses how “hours of congestion” have been used as an innovative transportation MOE. This concept has been applied successfully to two major studies in the Washington, D.C., USA, metropolitan area: • the Capital Beltway Major Investment Study (MIS) (a freeway corridor); and • the Route 1 Corridor Study (an arterial corridor). The hours of congestion MOE is easy to understand and provides an excellent means for screening a large number of preliminary alternatives before more detailed analyses (such as simulation) is conducted for a smaller number of potentially viable alternatives.