Route familiarity has been found greatly associated with driver behaviour and road traffic safety. This study aimed to find a method for measuring route familiarity. We propose a route familiarity measurement based on previous research results on familiarity in the field of psychology considering the process of driver’s familiarity and forgetting value about the route. The first step is to initialize the value of route familiarity considering the factor of previous driving experience on routes similar to the studied route. The second step is to update the value considering the factors of driver's learning during the total travelling time on the studied route and forgetting value during the time interval. The more previous experience the driver has, the higher the value of driver’s learning of the studied route environment of the travelling will be. For the same amount of increase in the value of experience, the increase of route familiarity value is larger when the value of experience is little, and the increase of route familiarity value is smaller when the value of experience is great.

traffic safety;route familiarity;measurement;previous experience