Dummy speed cameras on the A34 have been making a fool out of motorists because none of them contained any film.

The empty cameras watched over drivers between the Pear Tree interchange in Oxford and Weston-on-the-Green on the A34 since September while workmen dug up the road.

But not a single driver was caught breaking the reduced 40mph limit because none of the temporary roadside boxes ever contained cameras or film.

Similar fake temporary speed cameras were also installed during roadworks on Oxford's Northern Bypass.

Dan Campsall, spokesman for the Thames Valley Safer Roads Partnership, said: "We believe that the presence of the cameras did have an impact on vehicle speeds and are pleased to say that the safety record at the site was excellent.

"The Safer Roads Partnership and Highways Agency would like to thank drivers for their patience and co-operation through the period of the roadworks. In the event that future road works present similar issues, it is likely that mobile enforcement will be introduced to supplement the presence of fixed cameras."

Six speed cameras were put up on the northbound and the southbound carriageways of the A34 when roadworks began back in September 2005.

They were finally taken down when the road was fully reopened on Thursday ahead of the Easter Bank Holiday.

Signs warned drivers of the reduced limit from 70mph to 40mph and the threat of speed cameras.

But due to the variable changes in the speed limits and use of contraflow they were never able to be used.

Cash for the cameras was paid for by the contractors carrying out the roadworks and did not cost the taxpayer a penny, the spokesman added.

Empty cameras on Oxford's Northern Bypass during roadworks between Green Road Roundabout and Cutteslowe Roadabout in December also led to no fines or penalty points being issued.