Figures show 12% of Thames Valley speed cameras work
Only 12% of Thames Valley Police's 238 fixed speed cameras are operational at any one time, an investigation by consumer watchdog Which? has found.
Oxfordshire's fixed cameras were switched off in July after the county council withdrew £600,000 due to cuts.
Thames Valley Road Safety Partnership - made up of police, fire and councils - said speed cameras were designed to slow drivers down, not to fine them.
Across England and Wales 47% of cameras work at any one time, the figures said.
Police forces across England and Wales released the figures to Which? under freedom of information laws.
The study also highlighted big regional differences, with all 60 cameras in Sussex working compared to just 10% of Lancashire's 287 sites.
Which? said most areas rotated the working part of their cameras at random or in response to speed levels or accident statistics.