Table 2.

Studies with roadway and environmental factors.

Study	Authors (year)	Roadway characteristics	Environmental characteristics
12	Abdel-Aty and Abdalla (2004)	Curvature, existence of barriers, median width and type, pavement surface, ramps, shoulder width and type	–
13	Kashani and Mohaymany (2011)	Shoulder type	Lighting conditions, Pavement conditions (function of precipitation), Weather conditions
14	Jung et al. (2016)	Curvature, lane width, number of lanes, pavement surface, shoulder width, speed limit	Lighting conditions, rainfall intensity, temperature, wind direction, wind speed
15	Shi et al. (2018)	Curvature, existence of barriers, pavement surface, road markings, traffic signs	–
16	Yasmin et al. (2018)	Median width, number of lanes, ramps, shoulder width, speed limit	Weather conditions
17	Ali et al. (2019)	–	Pavement conditions, visibility conditions, weather conditions
18	Wang and Prato (2019)	Curvature, gradient	Pavement conditions, weather conditions