Why do drivers change route? effect of graphical route information panels

Studies that explore drivers´ decision behaviour under the graphical route information panels (GRIPs) via the discrete choice models have rarely been reported. In this paper, drivers´ route choice response to the GRIPs is quantitatively analysed by using the discrete choice models through a case study of a real-life GRIP in Shanghai, China. A logit model for predicting the route choice probabilities is developed to capture the relationship between the route choice probability, the driver attributes and the GRIP messages, respectively. The modelling results show that the drivers who have a larger annual driving mileage, access the traffic information via the electronic message signs in daily life highly value the GRIPs and drive their car mainly for the commuting purpose are more likely to divert from the original route to the alternate route under the GRIP; a driver´s perceived delay of the original route has a positive effect on his diversion decision under the GRIP; there exist differences in the GRIP response behaviour; the drivers are more likely to divert when the GRIP displays `red´ to indicate severe congestion on the original route; the female drivers are more sensitive to `red´ and more likely to divert.