Roadway network productivity assessment : system-wide analysis under variant travel demand

2008PDFTech ReportFHWA-HOP-09-019DTFH61-05-D-00002Travel demand managementTraffic congestionPerformance measurementUnited States. Federal Highway AdministrationJung, SoojungWunderlich, KarlNoblis, Inc.United States. Federal Highway AdministrationNTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic FlowNTL-OPERATIONS AND TRAFFIC CONTROLS-CongestionFederal Highway AdministrationThe analysis documented in this report examines the hypothesis that the system-wide productivity of a metropolitan freeway system in peak periods is higher in moderate travel demand conditions than in excessive travel demand conditions. The approach in this effort characterizes system-wide productivity by aggregating link-level speed and traffic volume (count) data. The study utilized 2007 Los Angeles and Chicago traffic data (both flow and speed) archived as part of the Urban Congestion Report (UCR) databases. In addition, an extensive archive of incident, work zone and weather data were available to identify the underlying conditions related to congestion patterns and bottleneck locations in the network. System-wide travel demand, delay and productivity were estimated for two Mondays in September-October 2007. One day was the worst congested Monday (September 10 2007) during the two-month period and the other Columbus Day (October 8 2007). Our a priori expectation was that travel demand on Columbus Day would be lower than on September 10 2007 since government and other workers receive a paid holiday on Columbus Day. Several measures of productivity based on a combination of flow and speed data were developed to capture system-level efficiencies of the freeway networks. The study suggests that higher system-level productivity and efficiency can be observed when travel demand is observed to closely match overall system capacity, resulting in less frequent onset and reduced duration of freeway breakdown conditions. By reducing demand and preventing congestion from taking hold, demand management through pricing or other mechanisms could recover the daily waste of time and drop in freeway system productivity that occurs on congested highways when traffic flow breaks down