Only one in five speed cameras in Scotland are actually working at any given time, according to new figures.
Scotland’s safety camera partnerships – which operate in conjunction with local police, councils and other authorities – run 169 of the roadside devices across the country.
But statistics released under freedom of information laws show only 20% are active at any given time.
The total represents a drop from the one in three cameras working in 2011.
Road safety campaigners said the figures were “disappointing” – but safety camera bosses insisted the “deterrence effect” remained even if the devices were not always working.
Scotland’s eight safety camera partnerships were asked to disclose how many were operational for a full week in June.
Four of the eight authorities – North East, Lothian and Borders, Strathclyde and Tayside – run fixed cameras, while the remainder – Central Scotland, Dumfries and Galloway, Fife and Northern – have only mobile camera vans.
The North East Safety Camera Partnership said it had five working devices across 25 sites.
Strathclyde reported 15 out of 63, Tayside three out of 14 and Lothian and Borders 11 out of 67.
Ed Morrow, campaigns officer for road safety charity Brake, said: “It is disappointing that safety camera partnerships in Scotland are not making full use of the resources available to them to stop speeding drivers putting lives at risk.
“Brake fully supports the use of speed cameras, which are proven to cut speeds and save lives.”
Neil Macgilivray, spokesman for Scotland’s safety camera partnerships, said: “The purpose of safety cameras is to deter drivers from risking public safety and breaking the law.
“Cameras have always been rotated on a regular basis and, as it is not possible for a driver to tell whether or not a camera housing contains a live camera at any particular time, it must be assumed that the camera housing is actively enforcing against speeding.”