Abstract
An accident risk is considered to be affected by a brightness change of the road, especially when a vehicle is travelling at twilight time or around tunnel sections. In this study, Poisson regression analyses are carried out to investigate the impact of the brightness change on traffic accident risk. The accident record and the traffic counts on expressways in Shikoku Island from 2007 to 2010 are used in the analysis. As a result, it is shown that traffic accident risk is significantly higher both when a vehicle travels at the night time and when a vehicle travels on the tunnel exit section at the daylight time or at the twilight time.
