Several research efforts indicate that rural intersection lighting reduces nighttime crashes and is a cost-effective crash mitigation strategy. However, many Minnesota agencies do not routinely install streetlights at rural intersections. This study evaluated the effectiveness of rural street lighting in reducing nighttime crashes at isolated rural intersections to provide more information to Minnesota agencies in making lighting decisions. A comparative analysis was used to evaluate 3,622 rural lighted and unlighted intersections from the Mn/DOT intersection database (US or Minnesota trunk highways). A linear regression model indicated relevant variables affecting the ratio of nighttime to total crashes are presence of street lighting, volume, and number of intersection approaches. The expected ratio of night to total crashes was 7% higher for unlighted intersections and was statistically significant. A before-and-after study was also used to evaluate the impact of lighting at 48 intersections. A 13% reduction in night crash frequency and a 36% decrease in the ratio of night to day crash rate occurred after lighting was installed. A Poisson regression model evaluated the change in night crash rate after installation of lighting. Only 33 of the 48 intersections were used in this analysis since initial results were not conclusive when intersections with fewer than 3 years of before or after crash data were included. Final results indicated that the night crash rate was lower after lighting was installed and was statistically significant. The expected night crash rate before lighting was installed was 59% higher than after lighting was installed. (Author/publisher)
Abstract