A study has shown that more than 50% of fixed speed cameras in England and Wales are not operational at any given time.
Speeding motorists' chances of being caught were more in Sussex, with all of its 60 cameras working, but much less in Lancashire where only one in ten cameras is operational, a study by Which? magazine found.
Overall, fewer than half (47%) of all cameras in England and Wales were in operation at any time, according to the study, which also found that many of the yellow boxes did not actually have cameras inside them.
Under the Freedom of Information Act, the magazine questioned all 43 police forces in England and Wales on how many fixed cameras they had installed and how of many of those were in good working condition.
Dorset, Hertfordshire, Merseyside, Norfolk and Suffolk refused to answer, but the available results showed counties had between 10% and 100% of their cameras in operation.
Durham said it used a single mobile camera because there was no need for fixed cameras anywhere in the county, while Cleveland, North Yorkshire and Wiltshire also did not operate any fixed sites.
A spokeswoman for Durham constabulary told the magazine: "We're a largely rural constabulary and the mobile camera is an approach that seems to work for us."
Elsewhere, Cumbria Police had just 12 fixed cameras - one of the lowest totals in the investigation - but all were operational.
Staffordshire Police had 263 speed camera housings but just 11% were in operation, while Avon and Somerset had 54 sites of which 94% were operational.
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