Speed cameras in one county which were switched off last year due to spending cuts have been switched on again.
Thames Valley Police said 72 fixed camera sites and 89 mobile sites in Oxfordshire are resuming operations.
They were switched off on August 1 2010 after Oxfordshire County Council cut the authority's road safety grant.
Superintendent Rob Povey, head of roads policing for Thames Valley, said: "We think this is important because we know that speed kills and speed is dangerous.
"We have shown in Oxfordshire that speed has increased through monitoring limits and we have noticed an increase in fatalities and the number of people seriously injured in 2010. We know that speed enforcement does work as a deterrent to motorists."
Data released by Thames Valley Police shows in the six months after they were switched off, 83 people were injured in 62 accidents at the site of fixed cameras.
The figure for the same period the year before (August 2009 to January 2010) was 68 injuries in 60 accidents.
Across Oxford, 18 people were killed in road traffic accidents in the period, compared with 12 people the year before. The number of people seriously injured rose by 19 to 179.
Mr Povey said the money for switching on the cameras came from cutting back office costs and funding diverted from speed awareness courses.
Professor Stephen Glaister, director of the RAC Foundation, said speed cameras are "controversial" but their research suggested they prevent 800 fatalities and serious injuries each year.