Road traffic crashes are a major cause of death and injury, especially in low and middle-income countries. Worldwide, each year over a million people are killed and some ten million people are permanently disabled in road traffic crashes. Furthermore, it is estimated that road traffic injuries will have risen from ninth to third in world disease burden rankings by 2020, and will account for 2.3 million deaths each year globally.
Street lighting has been suggested as a relatively low-cost intervention with the potential to prevent traffic crashes. Street lighting may improve a driver's visual capabilities and ability to detect roadway hazards. However, it is also argued that street lighting could have an adverse effect on road safety; drivers may 'feel' safer because lighting gives them improved visibility which could result in them increasing speed and reducing concentration.
This systematic review was conducted to assess how street lighting affects the occurrence of road traffic crashes and associated injuries. The authors searched for all controlled trials comparing the effects of new street lighting with unlit roads, or improved street lighting with the pre-existing lighting level. They found 17 controlled before-after studies, all of which were conducted in high-income countries. Twelve studies investigated the effects of newly installed street lighting, four the effects of improved lighting and one investigated both new and improved lighting. Five of the studies compared the effects of street lighting with a separate area control, while the remaining 12 used data from a day-time control. The authors were able to pool crash or injury data from 15 of the studies. The risk of bias in these studies was judged to be high.
The results indicate that street lighting can prevent road traffic crashes, injuries and fatalities. This finding might be of particular interest to low and middle-income countries where the policy on street lighting is less developed and the installation of suitable lighting systems is less common than in high-income countries. However, further well designed studies are needed to determine the effectiveness of street lighting in middle and low-income countries.