Evaluating the impacts of changeable message signs on traffic diversion

The Ontario Ministry of Transportation has 17 CMS installed strategically upstream of Express-Collector transfer locations on Highway 401 in Toronto, Canada. Motorists are informed by the CMS 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 impact of CMS messages on traffic diversion using 3 years of loop detector data from 2003 to 2005. We have found that on average a CMS message change can alter the diversion rate by up to around 5%, and can shift up to around 300 vph. These numbers depend strongly on the specific initial and final messages, and on the location of the CMS. Drivers' reactions to CMS messages tend to be higher in the afternoon than in the morning. The impacts of CMS messages on drivers appear to be diminishing over the years