Using Archived Data to Systematically Identify and Prioritize Freeway Bottlenecks

Bottlenecks are critical components of freeway systems and are of increasing importance as congestion worsens in major urban areas. In the U.S., the Federal Highway Administration has launched a new initiative aimed at identifying key bottlenecks in each state. In Oregon, a freeway data archive has been established that stores vehicular count, occupancy, and speed data from over 600 locations at 20-second intervals. Performance measurement tools are also available and report on travel time, delay, vehicle miles traveled and vehicle hours traveled. In addition, basic statistical tools are included that can report on travel reliability across days, weeks, months and years. The Portland, Oregon metropolitan region is known for its innovative transportation planning and multimodal transportation system. This paper describes procedures used to develop an automated system to identify freeway bottlenecks using historical data within an archived data user service environment. Efforts are aimed at identification and display of active bottleneck features using graphical tools. This research aims to detect bottleneck activation in real time and to expand the use of reliability techniques. Efforts are aimed at improving the prioritization of improvements and implementation of operational strategies. With the availability of archived data, new analysis tools are possible at relatively low cost, with no new data collection.