Alley gates are lockable gates installed to prevent access by offenders to alleyways, such as those which run along the rear of older-style terraced housing in the UK. While normally a burglary prevention tool, alley gates can also prevent other crimes such as littering and anti-social behaviour by preventing access to alleys by non-residents and better controlling the space.
Alley gates are usually made of iron or steel, and are bespoke in relation to the requirements and specifications of an individual alley. The residents of homes adjacent to the gated alley are then left to operate the gates, either using keys or key-code combinations.
This narrative is based on one review of 43 studies. The outcome measured was a reduction in police recorded burglaries.
Overall, the evidence suggests that alley gating has reduced crime.
When the authors calculated an overall effect size using six studies with higher quality methodological designs, a statistically significant reduction in domestic burglary rates was found in comparison to control areas.
Four of the six individual studies included in a statistical meta-analysis reported statistically significant reductions in burglary, and none reported increases.
It is important to note that the review authors found no evidence of crime being displaced to surrounding areas, but instead a diffusion of benefits was found. That is, burglary rates in the areas surrounding the gated areas showed a decrease, though this decrease was not statistically significant.
The review was sufficiently systematic that most forms of bias that could influence the study conclusions can be ruled out.
The review considers many elements of validity, conducting relevant statistical analyses and using multiple coders to ensure the accuracy of information collected. It considered the possibility of publication bias, as well as ensuring that only studies of comparable quality were pooled to create an overall effect size. The authors also conducted analyses of possible displacement and diffusion of benefits following the intervention.
The review identified a number of different ways in which alley gates may reduce, or increase crime. However, information was not available from the primary studies to test whether these mechanisms were responsible for the outcome patterns observed. Specifically these were:
Within the review, a variety of contextual factors, which could impact upon the effectiveness of alley gates were discussed, as listed below. The absence of data in the primary studies meant that these could not be tested.
The review authors suggest a number of combinations of contexts and mechanisms which may be favourable (or not) to reducing crime:
The review noted a number of important factors which must be considered to successfully implement alley gates.
There must be full consultation with residents leading to their consent to the scheme. The proportion of residents who need to agree to gates being installed may vary depending on the area. This ties into the importance of resident commitment to the implementation and usage of the gates. Residents must agree to the rules about how the gates are to be used, and accept responsibility for implementing these rules.
Early consultation with local authorities is highlighted by the review, so that local services such as refuse collection and the emergency services are not compromised by the implementation of the alley gates. The status of the alley is also important – who owns the alley may affect the installation of the gates. If the alley is a public right of way it is potentially more complicated to get permission to install the gates. If the alleys are owned by the home-owners, it may also require all owners to agree, which may be complicated in areas with high levels of rented properties. Finally the features of the gates themselves are important – the gates and the locking mechanisms must suit the users. If keys are to be used, then everyone who requires access to the alley must have a key.
The review synthesised information about the costs of alley gates from the primary studies where provided, and conducted a cost-benefit analysis of the 5 studies which provided enough information to do so. The cost per gate for the alley gates ranged from £158 to £1453.21 across 6 studies, with an average cost per gate of £728. The costs of the gates varied significantly due to the different requirements for the gates in different areas. Only one of the studies showed a negative cost benefit ratio, and conservative estimates of the benefit to cost ratios ranged from minus £2.79 for each £1 spent, to £2.19 benefit per £1 spent. Where appropriate, the primary studies included not only the costs of the alley gates, but also those for other interventions implemented.
Overall, the evidence suggests that alley gating has reduced crime. A diffusion of benefits to surrounding areas has also been detected.
Alley gates work by reducing the access of potential offenders to the rear of houses, and while commonly a burglary reduction initiative, can also reduce other crimes that occur in alleys such as anti-social behaviour and littering. The residents of the alleys to be gated should be consulted and be willing to use the gates correctly in order for them to be effective. The gates were found to generally be cost effective, although the cost of the gates varied widely depending upon location and requirements.
Review: Sidebottom, A., Tompson, L., Thornton, A., Bullock, K., Tilley, N., Bowers, K. and Johnson, S. D. (2015) Gating Alleys to Reduce Crime: A Meta-Analysis and Realist Synthesis
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.