Community speed-watch schemes have been endorsed by the Audit Commission as an example of cost-effective, co-production of local services.
Almost one-third of police forces in England and Wales are now training villagers to use speed guns, commission chief executive Steve Bundred told this week's Chartered Institute of Public Finance and Accounts  conference.
It follows the success of a scheme in Avon and Somerset, where speeding drivers reported by volunteers receive police letters warning of prosecution if they repeat the offence.
Involving users in the design and delivery of services offered a way to sustain improving performance as funding support levelled off, Bundred argued.