What is the effect of reduced street lighting on crime and road traffic injuries at night? A mixed-methods study

Background: Some local authorities have reduced street lighting at night to save energy, but little is known about impacts on public health or about public concerns about impacts on well-being. Aim: To evaluate the effect of reduced street lighting on crime and road traffic injuries. Design: A mixed-methods study comprising a rapid appraisal, a controlled interrupted time series analysis and a cost–benefit analysis (CBA). Setting: England and Wales. Target population: Residents and workers in eight case study areas; road traffic casualties and victims of crime. Interventions evaluated: Switch-off (i.e. lights permanently turned off), part-night lighting (e.g. lights switched off between 12 a.m. and 6 a.m.), dimming lights and white lights/light-emitting diodes (LEDs). Outcomes: Public views about implications on well-being; road traffic injury data (STATS19: http://data.gov.uk/dataset/road-accidents-safety-data) obtained for the period 2000–13; crime data (Police.uk: data.police.uk) obtained for the period December 2010–December 2013. Detailed crime data were obtained from one police force for a methodological study of the spatial level at which Police.uk data are valid for analysis. Statistical methods: Road traffic collisions were analysed at street segment level. Regression models were used to estimate changes in daytime and night-time collision rates associated with lighting interventions. The ratio of night-time and daytime changes was considered the best estimate of change in night-time collisions following each lighting intervention. Police.uk crime data were found to be reliable when analysed at middle super output area (MSOA) level. For crime, the analysis used the proportion of total km of road in each MSOA with each lighting intervention. Regression models controlled for yearly and monthly trends and were fitted in each geographical region and police force. Effect estimates were pooled in random-effects meta-analyses. Results: Public concerns centred on personal security, road safety, crime, fear of crime, sleep quality and being able to see the night sky. Street lighting reductions went largely unnoticed or had only marginal impacts on well-being, but for a minority of people switch-off and part-night lighting elicited concerns about fear of the dark, modernity and local governance. Street lighting data were obtained from 62 local authorities. There was no evidence that reduced street lighting was associated with road traffic collisions at night. There was significant heterogeneity in the estimated effects on crime at police force level. Overall, there was no evidence that reduced street lighting was associated with crime. There was weak evidence for a reduction in crime associated with dimming [rate ratio (RR) 0.84, 95% confidence interval (CI) 0.70 to 1.02] and white light (RR 0.89, 95% CI 0.77 to 1.03). The CBA suggests that part-night lighting may represent a net benefit to local authorities. Limitations: The study did not account for the impacts of other safety/crime prevention initiatives (e.g. improved road markings; closed-circuit television), and so associations may be partly attributable to these initiatives. The CBA was unable to include potentially important impacts such as fear of crime and reduced mobility. Conclusion: This study found little evidence of harmful effects of switch-off, part-night lighting, dimming or changes to white light/LEDs on levels of road traffic collisions or crime in England and Wales. However, the public were also concerned about other health outcomes. Research is needed to understand how lighting affects opportunities for crime prevention and how these vary by context. Research is needed also on other public health impacts of light at night. Funding: The National Institute for Health Research Public Health Research programme