Speed cameras were out for the first time today on the M40.

Thames Valley Safer Roads Partnership has started parking speed camera vans on bridges over the motorway in Oxfordshire.

But the roads partnership will not install signs warning drivers of the enforcement as it is too expensive.

Spokesman Dan Campsall said the signs would cost up to £25,000 each to buy and install.

The enforcement follows an increase in accidents and deaths on the M40 for the fourth successive year.

There have been five deaths and 39 serious injuries on the motorway in Oxfordshire this year alone.

Claire Benson, head of specialist units road policing, said: "We believe that as part of the overall package of road safety measures, speed enforcement will help to reverse the current trends and reduce casualties on the motorway."

Andrew Howard, head of road safety at AA, said signs should be installed to stop motorists’ claims that the safety partnership is out to fine drivers, not encourage them to slow down.

He said: "The idea should be to deter people from speeding, not to catch speeders.

"The first most people will be aware the motorway is being enforced is when fines land on their doorstep."

From tomorrow, anyone caught speeding on the M40 will face a £60 fine and three penalty points.