Only a quarter of speed cameras in West Yorkshire are switched on, police have admitted.
West Yorkshire Police has revealed that only 98 of its 396 fixed speed cameras are actually catching offenders.
West Yorkshire has one of the lowest rates of active cameras (25%), a Freedom of Information request by the Press Association (PA) found.
The county has one of the highest amount of fixed cameras in the country, according to the data – more than twice as many as the whole of Scotland (173) or Greater Manchester (177).
The PA probe found that across the UK only about half of fixed speed cameras are on.
The figures cover all police fixed speed cameras, but not the mobile devices forces also use.
Other areas where a quarter or less are switched on are; Kent (25%), South Yorkshire (24%), Greater Manchester (24%), Cheshire (17%), Staffordshire (5%).
The forces which said none of their fixed speed cameras were active were Cleveland, Durham, North Yorkshire and Northamptonshire.
The Northamptonshire force said it turned its cameras off in April 2011, but has left the structures in place to deter speeders.
Staffordshire Police have 272 fixed cameras across their patch, but just 14 of them are active, while the Derbyshire force operates 112 cameras with just 10 of them catching speeders.
Huddersfield based road safety charity Brake described the figures as concerning and called for all cameras to be switched on, while AA president Edmund King said the high number of inactive cameras was down to pressure on budgets.
A spokeswoman for the National Police Chiefs’ Council said the decision to use cameras was “an operational matter”, adding that “all forces have individual responsibility for their use of speed cameras”.
Jason Wakeford, director of campaigns for Brake, said: “A staggering 1,800 people lost their lives on British roads last year and speeding is a factor in thousands of crashes.
“Speed cameras are a proven, cost-effective way of reducing deadly collisions and so it’s critical they are operational.
“We are concerned to see figures which suggest so many are switched off and would urge they are urgently put back into action.”
Edmund King from the AA, said: “Many of the empty yellow cases are due to cuts in road safety grants and the fact that digital cameras, although more effective, are very expensive.
“It is also reflective of the fact that proceeds from cameras are no longer allowed to be ring-fenced to be reinvested into yet more cameras as now all the money goes to the treasury.”
But he warned motorists against gambling on a camera being inactive.
He said: “Drivers who play Russian roulette with fixed-site speed cameras are playing a dangerous game. Our advice is stick to the limits rather than gambling on the yellow boxes.”
Claire Armstrong, co-founder of lobby group Safe Speed, which campaigns for more traffic police officers rather than speed cameras, said the investigation “proves police forces don’t believe in cameras”.
She said: “Forces are conning the public into thinking cameras are there for road safety because, if they really thought that, every single one of them would be on.
“They are a flawed road safety policy and the only way to truly improve that is with more traffic police officers on the roads.”
She added: “I am glad there are only 52% working – we’d actually like to see less.”
Neil Greig, spokesman for the charity IAM RoadSmart, which campaigns to make roads safer by improving driver and rider skills, said it believed all speed cameras should be active.
He said: “Drivers should be in no doubt that every yellow box they pass is active and police forces and safety camera partnerships should all be aiming for their cameras to be vigilant 100% of the time.”
Steve Gooding, director of the RAC Foundation, said: “It would be a dangerous and foolish driver who was tempted to speed because they thought they’d get away with it.
“Not only are cameras routinely moved between housings, police also use mobile cameras, while several hundred miles of British roads are now being monitored by average speed check systems.
“The majority of the public back the use of speed cameras, but the location and effectiveness of the devices should be the subject of regular scrutiny.”
The Department for Transport was contacted for comment.