Study Details

Study Title: Safety Effects of Street Illuminance at Urban Signalized Intersections in Florida

Authors: Wei et al.

Publication Date: JAN, 2016

Abstract: Nighttime crashes are overrepresented in the nationwide and statewide roadway systems. Nighttime safety at signalized intersections in urban areas receives more attention because of frequent and serious vehicle-to-vehicle and vehicle-to-pedestrian/bicyclist traffic conflicts at night. Street illumination has been proven to be an effective countermeasure for increasing the visibility of intersection and reducing nighttime crashes. However, the safety effects of illuminance at urban signalized intersections were not well documented. This paper aims to investigate the impacts of illuminance on both nighttime crash occurrence and nighttime crash injury severity at urban signalized intersections. Illuminance data and crash data for a sample of 91 signalized intersections were collected from Tampa Bay, Florida. The negative binomial model and the probit model were developed to examine the safety effects of intersection illuminance in terms of crash frequency and the risk of fatality and severe injury, respectively. The models show that increasing intersection illuminance from low (< 0.2 fc) to medium (≥ 0.2 fc and <1.1 fc) can reduce nighttime crash frequency and night-to-day crash ratio by approximately 50%. If illuminance is kept at 0.9 fc or higher, the risk of fatality and severe injury significantly decreases, especially for pedestrian/bicycle involved 16 crashes, head-on crashes, and angle crashes.

Study Citation: Wang, Z, F. Wei, P. S. Lin, P. P. Hsu, S. Ozkul, J. Jackman, and M. Bato. "Safety Effects of Street Illuminance at Urban Signalized Intersections in Florida," Presented at the 96th Annual Meeting of the Transportation Research Board, Paper No. 16-6376, Washington, D.C., (2017).


CMFs Associated With This Study

Category: Highway lighting

Countermeasure: Improve lighting

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.158 -15.8 3 Stars Other All Not specified Urban

Countermeasure: increase intersection illuminance from low (< 0.2 fc) to medium (≥ 0.2 fc and <1.1 fc)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.47 53 3 Stars Nighttime All Not specified Urban
0.48 52 3 Stars Nighttime All Not specified Urban
0.519 48.1 3 Stars Other All Not specified Urban