Crime Reduction Toolkit FAQs

Below are answers to some of the most commonly asked questions about the Crime Reduction Toolkit.  However if you would like any additional information, please email

What is the Crime Reduction Toolkit?
The Crime Reduction Toolkit summarises the best available research evidence on what works to reduce crime. It uses the EMMIE framework to present evidence from systematic reviews of research on crime reduction interventions in a format that helps users to access and understand it quickly.

How can the Toolkit help me?
The Toolkit can help you to understand what reduces crime (and what doesn't) according to the best available evidence.  You can also find out how and where interventions work best, how to implement them and what they might cost. Clicking on the intervention title provides a more detailed summary of the findings.

What is the difference between the Toolkit in table form and the Toolkit in bubble form?
Both formats draw on the same research evidence relating to the same crime reduction interventions.  The main difference between the two formats is the way in which the evidence is presented.  The bubble version allows you to access the evidence relevant to the crime problem you are trying to tackle and is designed to be more interactive. The table version presents a straightforward list of the interventions.

What is a systematic review?
A systematic review summarises the research evidence from a number of studies on a particular topic and uses strict criteria to exclude studies that do not fit certain quality and methodological requirements. Some systematic reviews include meta-analyses which use statistical tests to estimate the overall effect of an intervention by combining data from multiple studies. Only interventions that have been subject to a systematic review have been included on the Crime Reduction Toolkit.   

How were the studies coded?
Our method statement summarises the approach taken to create the What Works Crime Reduction Toolkit.  It can be broken down into 4 stages:

Stage One:  Searching for relevant systematic reviews
Stage Two:  Devising a system to capture and assess the quality of evidence from systematic reviews
Stage Three:  Coding the studies
Stage Four:  Translating EMMIE into a practical tool

What is EMMIE?
Evidence is presented using the framework EMMIE. EMMIE is a rating and ranking system which was developed by academics at University College London to help practitioners and decision-makers to access the evidence-base easily and quickly. EMMIE rates each intervention against the following five dimensions:

  • Effect
Impact on crimeWhether the evidence suggests the intervention led to an increase, decrease or had no impact on crime.
  • Mechanism
How it worksWhat is it about the intervention that could explain its effect?
  • Moderators
Where it worksIn what circumstances and contexts is the intervention likely to work / not work?
  • Implementation
How to do itWhat conditions should be considered when implementing an intervention locally?
  • Economic cost
How much it costs What direct or indirect costs are associated with the intervention and is there evidence of cost benefits?

For further information go to About the Crime Reduction Toolkit and EMMIE or see our Quick Start Guide to EMMIE infographic.

What is meant by the quality of evidence?
The quality scale shows you the quality of the research evidence. This ranges from no information (where we cannot comment on quality) to very good quality where we can feel confident in relying on the findings i.e. most forms of bias that could influence the study conclusions can be ruled out.

Read more about the quality scale

What is meant by the impact of an intervention on crime?
The effect scale shows you what the research evidence suggests about the effect of an intervention on reducing crime.  The scale ranges from interventions which show an overall decrease in crime to those which show an overall increase. 

Read more about the effect scale

Definitions of terms 

AdultInterventions that target adults and interventions where no reference is made to young people or children so it can be assumed the research relates to adults.
Young peopleGenerally applied to interventions where population is above minimum school leaving age but may be younger than 18 years of age (e.g. applied to driving interventions to include newly qualified drivers).  Also applied to young adult populations sometimes described by reviewers as delinquents.
​ChildApplied to populations of under 18 years.  Sometimes applied in conjunction with young persons, where the population is 17 and above.​
EnvironmentApplied to interventions where a location e.g. a car park or residential street, is the target.
PreventionInterventions focussed on preventing crimes from taking place.  Includes situational prevention and people-based interventions.
DiversionInterventions targeting 'at risk' groups to divert them from committing crime.
ReoffendingInterventions that deal with the offender after an offence has taken place to prevent repeat offending.

The factors filters (e.g. alcohol, drugs, gangs) are applied to interventions that are explicitly linked to that particular factor. Interventions can be linked to factors by the focus of the intervention itself (e.g. Policies related to alcohol sales – so are linked by 'alcohol') or by the outcomes the intervention has been tested against (e.g. the effectiveness of youth curfews has been tested specifically on gang-related crime).

Some interventions in the toolkit may also be effective at tackling factors related to crime, but if they have not been explicitly linked to such factors, the filter has not been applied.

Factor filters are always applied to Problem Orientated Policing (POP). POP is a problem solving approach to develop targeted interventions, rather than an intervention per se. Therefore, a POP approach can be applied to any crime and disorder problem.


If you have any questions about the Crime Reduction Toolkit, please email