Following about 40 years of successful deployment of coordinated traffic-responsive ramp control, a new generation is being developed for Minnesota's freeways based on density measurements, rather than flow rates. This was motivated from recent research indicating that the critical value of density at which capacity is observed is less sensitive and more stable than capacity, thereby allowing the opportunity for more effective control. The main goals of the new approach are to delay the onset of the breakdown and accelerate system recovery when ramp metering is disabled due to the violation of maximum allowable ramp waiting times. This is obtained by a dynamic zone partitioning of the freeway network to identify critical bottleneck locations and coordinated balancing of ramp delays, which aims to avoid mainline breakdown. The effectiveness of the new control strategy is assessed by comparison with the currently deployed version of the stratified zone metering algorithm through microscopic simulation of a real 12-mi 17-ramp freeway section. Simulations show a decrease in delays of mainline and ramp traffic and an improvement of 8% in overall system delays while avoiding maximum ramp delay violations.
|Original language||English (US)|
|Number of pages||11|
|Journal||IEEE Transactions on Intelligent Transportation Systems|
|State||Published - Dec 2011|
Bibliographical noteFunding Information:
Manuscript received November 10, 2010; revised April 27, 2011 and July 26, 2011; accepted August 8, 2011. Date of publication September 8, 2011; date of current version December 5, 2011. This work was supported by the Intelligent Transportation Systems Institute of the Center for Transportation Studies, University of Minnesota. The Associate Editor for this paper was M. Chowdhury.
- ramp metering
- traffic congestion
- traffic control