Street lighting

Impact on crime
Evidence quality 4
Effect
How it works
cog full Evidence quality 3
Mechanism
Where it works
where full Evidence quality 2
Moderator
How to do it
what empty Evidence quality 0
Implementation
What it costs
cost full Evidence quality 0
Economic cost

What is the focus of the intervention?

Improved street lighting is a form of situational crime prevention that involves increasing the levels of illumination on the street or in other public spaces.  It is intended to serve many purposes, including accident prevention, marketing and the reduction of crime. This review covers crime reduction only.

This narrative is primarily based on one systematic review covering 13 studies.

EFFECT

How effective is it?

​Overall, the evidence suggests that the intervention can reduce crime. Across the 13 studies reviewed, both violent and property crime was reduced by an average of 21 per cent in areas with improved street lighting compared to areas without.

There were no studies for which a statistically significant backfire effect (where crime increased) was reported.

How strong is the evidence?

​The review was sufficiently systematic that most forms of bias that could influence the study conclusions can be ruled out.  However, it is worth noting that the comparison areas used to estimate the impact of improved street lighting in the primary evaluations were sometimes adjacent to the areas in which street lighting was improved.  The authors of the review note that this could have affected the estimates of the impact of intervention. There may, for example, have been a displacement effect or a diffusion of benefits.​

MECHANISM

How does it work?

​The review provides a description of some of the possible mechanisms through which street lighting might reduce crime, and the testable predictions generated from them.

Specifically, improved street lighting might reduce crime by –  

  • increasing visibility and the number of people that use the street.  This could lead to increased - or more effective - natural surveillance that may ​deter crime.  If this mechanism explained how improved street lighting reduced crime in the studies considered, then the effects of street lighting should be greatest during the hours of darkness.  However, in the case of the studies reviewed, for those that only examined the impact of improved street lighting on levels of crime at night (four evaluations), there was no evidence of an impact on crime.  In contrast, those studies (9 in total) that examined changes in levels of crime during the day and night found a statistically significant impact on crime in the areas with improved street lighting, which suggests an alternative mechanism (see below).

  • demonstrating investment in the neighbourhood.  This has the potential to improve community conditions that could plausibly lead to residents caring more about their neighbourhood and consequently being more likely to take actions that might reduce​​ crime in them.  The finding that improved street lighting did not have an impact on crime solely after dark is consistent with this explanation. 

However, further systematic evidence is required to demonstrate that improved street lighting does influence community pride in a neighbourhood, which in turn​ stimulates resident activity or investment in their neighbourhood.  The review authors provided some evidence consistent with this explanation, but only for the UK studies conducted in Dudley and Stoke-on-Trent (see page 19 of the systematic review).  In Dudley, for example, evidence suggested that improved lighting contributed to an increase in residents' quality of life, and appeared to encourage them to obtain substantial government funding to pay for further improvements in their neighbourhood.​​

MODERATORS

In which contexts does it work best?

​The review discusses the possibility that reductions are likely to be greater if the existing lighting is poor and if the improvement in lighting is consi​​​derable.

The review authors conducted a basic analysis that compared outcomes in all reviewed studies from the UK and USA, by crime type and for crimes that occurred at night or throughout the day/night.  Using study data where available, they report that compared to similar comparison areas, for every 100 crimes:

(Country​ effects)

In the UK, an av​erage of 38 fewer crimes were observed in areas with improved street lighting (based on 5 studies).

In the US, an average of 7 fewer crimes were observed in areas with improved street lighting (based on 8 studies).

(By crime type)

For property crime, an average of 17 fewer crimes were observed in areas with improved street lighting (based on 9 studies).

For Violent crime, a​n average of 9 fewer crimes were observed in areas with improved street lighting (based on 9 studies).​​

(Time of day)

Looking at crime committed over 24 hours (day and night), an average of 30 fewer crimes were observed in areas with improved street ligh​ting (based on 9 studies).​

For night-time crime only, no fewer crimes were ob​​​served in areas with improved street lighting (based on 4 studies, all conducted in the USA).  

IMPLEMENTATION

What can be said about implementing this initiative?

The review provides little information on how to implement street lighting improvements although the authors suggest that a ‘marked improvement’ in lighting conditions is important.​​

ECONOMIC CONSIDERATIONS

How much might it cost?

The review does not mention costs (and/or benefits) and no formal economic analysis is provided.  However, the authors note that in the Dudley (UK) and Stoke-on-Trent (UK) studies, conducted by Painter and Farrington (2001) “the financial savings from reduced crimes greatly exceeded the financial costs of the improved street lighting installed” (see page 19 of the review).  A formal Economic Analysis is required to assess the costs of improved lighting more generally, however is should be kept in mind that costs will depend upon the types of lighting chosen, electricity prices and repair and maintenance costs – all of which can vary over time. ​​​​

General considerations

  • As the​ review states, improved street lighting is more likely to have an effect where lighting is initially poor.  ​

  • If impr​oved street lighting impacts upon crime by influencing community pride, it may be most effective in stable but underinvested communities (see pages 5 and 19 of the review).

  • Although none of the 13 studies included in the systematic review found a statistically significant backfire effect, it is possible that incre​ased visibility through improved street lighting could increase crime by enabling offenders to make better judgments of the vulnerability and attractiveness of potential targets.

  • In the overall review, it was not possible to examine geographic displacement or the diffusion of benefits to nearby locations.  However, in one study (see page 16 of the review) the findings suggested that crime was statistically significantly red​​uced in the areas nearby.

  • The studies in this review did not consider the impact on crime of recent changes in lighting technology such as the introduction of LED lamps, or changes in lighting schedules such as part-night lighting.

  • Improvements in stre​​et lighting levels can be criticised for adversely affecting light pollution, sleep (including of animals) and energy efficiency. 

  • Improved lighting levels m​​ight be necessary to the effective deployment of other crime prevention initiatives such as CCTV.

None of the UK studies covered in the review separated daytime crime from night-time crime in assessing effect. It is not, therefore, possible to conclude whethe​r or not it was street lighting improvements that reduced crime, or whether these improvements facilitated other mechanisms such as community cohesion (as is suggested by the four US studies).

Summary

Overall, the evidence suggests that improved street lighting can reduce crime. Crime (violent and property) reduced by an average of 21% in treatment areas where street lighting was increased, relative to comparison areas without increased street lighting. Exactly how this effect is achieved remains currently unknown.

Ratings for Individual Reviews

Review 1

How it works
cog full Evidence quality 3
Mechanism
Where it works
where full Evidence quality 2
Moderator
How to do it
what empty Evidence quality 0
Implementation
What it costs
cost full Evidence quality 0
Economic cost

Resources

Welsh, B., and Farrington, D.F. (2008). Effects of Improved Street Lighting on Crime. Campbell Collaboration Systematic Review. Campbell Collaboration: Norway. 

 

This narrative was prepared by UCL Jill Dando Institute and was co-funded by the College of Policing and the Economic and Social Research Council (ESRC).  ESRC Grant title: 'University Consortium for Evidence-Based Crime Reduction'.  Grant Ref: ES/L007223/1.

Uploaded on 19/02/15

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