There is no clear scientific evidence that increased outdoor lighting deters crimes. It may make us feel safer, but has not been shown to make us safer. A 2015 study published in the Journal of Epidemiology and Community Health found that streetlights don't prevent accidents or crime, but do cost a lot of money.

Do street lights prevent accidents?

Three trials compared street lighting with an area control on total crashes; pooled rate ratio (RR) = 0.45 (95% Confidence Interval (CI) 0.29 to 0.69). ... Authors' conclusions: The results from this systematic review suggests that street lighting may prevent road traffic crashes, injuries and fatalities.

Does lighting improve safety?

Appropriate lighting, without glare or shadows, can reduce eye fatigue and headaches; it can prevent workplace incidents by increasing the visibility of moving machinery and other safety hazards.