A Cochrane review included 17 controlled before-after studies of street lighting, all reporting crash data. Seven trials included a designated control site; the other ten collected data at one site with the day-time data being used as the control. None of the included studies examined the effect of street lighting in either low or middle-income countries. The methodological quality of the trials was generally poor.
Three trials compared street lighting with an area control on total crashes; pooled RR = 0.45 (95% CI 0.29 to 0.69). Two trials compared street lighting with an area control on total injury crashes (all severities); RR = 0.78 (95% CI 0.63 to 0.97). No trials compared the number of fatal crashes with an area control. Eleven trials compared street lighting with a day-time control on total crashes; pooled RR = 0.68 (95% CI 0.57 to 0.82). Six trials compared street lighting with a day-time control on total injury crashes; pooled RR = 0.68 (95% CI 0.61 to 0.77). Four trials compared street lighting with a day-time control on fatal crashes; pooled RR = 0.34 (95% CI 0.17 to 0.68).
Comment: The quality of evidence is downgraded by indirectness (most studies located for inclusion in this systematic review were published before 1990).