Coordination of Freeway Ramp Metering and Arterial Traffic Signals
On-ramp metering at freeway bottlenecks is an effective method of preventing capacity drop and reducing a freeway system’s delay. However, arterial traffic signals that facilitate access to freeway on-ramps operate independent of the traffic conditions on the freeway on-ramps. Consequently, the traffic signals employ long signal cycle lengths and thus long green durations to maximize capacity at the arterial signalized intersections. This often causes queue spillback on the freeway on-ramps and the surface street network. Queue override, a function that terminates or significantly relaxes the on-ramp metering rate whenever a sensor placed at the entrance of the on-ramp detects a potential queue spillover of the on-ramp vehicles on the adjacent surface streets, has become a widely accepted method of resolving queue spillback on the freeway on-ramps and nearby surface streets. Unfortunately, queue override releases the queue into the freeway and negates the benefit of ramp metering during the peak hours with recurrent freeway congestion. Recently, there has been significant interest in integrated corridor management (ICM) of facilities comprised of freeways and adjacent arterial streets. Significant benefits can be realized by preventing queue override and effectively storing the queued vehicles on the nearby arterial surface streets if the arterial traffic signals can account for traffic conditions on freeway on-ramps and avoid sending long platoons to the freeway on-ramp. A signal control strategy has been developed and tested through simulation. Field implementation is currently under preparation. This project is funded by Caltrans and joint work with Prof. Alexander Skabardonis and Dr. Xiao-yun Lu.
David Kan received his B.S. in Civil Engineering from the University of Illinois at Urbana Champaign in May 2013. He received his M.S. and Ph.D. in Civil Engineering from the University of California at Berkeley in May 2014 and August 2017, respectively. He has worked on the simulation phase of Coordination of Freeway Ramp Metering and Arterial Traffic Signals, as well as the FHWA sponsored project: Using Cooperative Adaptive Cruise Control (CACC) to form High-Performance Vehicle Stream.