Thames Valley Police will check ravers as they arrive and leave the Summer Sound System open-air event at an airfield in Turweston, near Buckingham.

About a dozen officers will check for dilated pupils, and monitor co-ordination and judgment.

If motorists fail or refuse the test, they can be arrested and have a blood sample taken to check for drugs such as ecstasy or cannabis.

Blood tests

Five people have died in car crashes in two years, after leaving the annual event organised by Gatecrasher Live Limited.

Inspector Peter Downing said: "We have to do something to address the issue of people driving under the influence of drugs and to prevent further tragedies occurring in the future.

"We're not looking to spoil people's fun.

"We want them to enjoy themselves, but in a safe environment.

"We also want them to get home safely from the event."

The tests include requiring a driver to walk in a straight line, turn and continue walking without losing balance.

Original trials for sobriety testing were carried out by the Strathclyde and Northamptonshire police forces.

The event is being held on Saturday, 22 June.