The Ontario Ministry of Transportation has 27 CMSs installed strategically upstream of Express-Collector transfer locations on Highway 401 in Toronto, Canada. Motorists are informed by the CMSs of traffic conditions downstream of the transfer location to help them decide whether to take the next transfer. Loop detectors are installed at the transfer locations to measure traffic flow. This paper evaluates the dynamic impacts of CMS messages on traffic diversion using 3 years of loop detector data from 2003 to 2005. Based on time-series plots of aggregated diversion rates, we find that the initial transient response to the message change is quite significant, suggesting the message changes (rather than simply the messages themselves alone) play a vital role in influencing downstream diversion. Aggregate diversion rate plots also reveal that CMSs react to diversion rate changes in many occasions and close a feedback control loop that effectively regulates the downstream diversion rates. A three year comparison study suggests a slight decreasing trend in drivers reliance to messages displayed on the signs. Statistical significance, however, is low and further workis required to verify this trend.
Abstract