This paper deals with an investigation on whether the change in the viewing environment at dusk has a connection with the occurrence of traffic accidents by statistical analysis of data on traffic accidents in Japan. In this paper, dusk is considered to be a time period of civil twilight which is about 30 minutes in Tokyo. The target area is limited so that the time period for dusk would be basically the same time. As a result, the author could not recognize a tendency for traffic accidents to occur with especial frequency in the period of dusk. In addition, there was analysis in terms of the ages of the drivers (drivers in their 20s, 40s and 65 years or over). Judging from data on traffic accidents, the author could not confirm a tendency toward more frequent traffic accidents at dusk in any of the age groups, including drivers of advanced age.