TECHNIQUES FOR MANAGING FREEWAY TRAFFIC CONGESTION

Urban freeway congestion is categorized into 2 types, recurring congestion and non-recurring congestion, and their causes are noted. Recurring congestion management techniques are of two types. (1) Supply management techniques consist of entrance ramp control, exit ramp control, mainline control, priority control, and corridor control. (2) Demand management techniques include work rescheduling, ridesharing, park-and-ride facilities, and transit service improvements. Geometric improvement techniques are another approach to managing recurring congestion. Non-recurring congestion may be managed by freeway surveillance systems (motorist call systems, citizen-band radio, police and service patrols, aerial surveillance, closed-circuit television, detector-based surveillance, cooperative motorist aid system), and freeway incident management systems. Integrated motorist information systems (IMIS) designed to encourage mainline motorists upstream of the incident to use an alternate route to bypass the incident site) are also described.