A major road tunnel will be closed for four hours when it is used to test how emergency services cope with a disaster.

Experts plan to create a realistic accident inside the Southwick tunnel on the A27 near Shoreham.

Operation Parris will involve closing the tunnel between 8pm and midnight on Monday.

The scenario, which will be played out by the fire brigade, ambulance service and the police, will involve the crash of a minibus packed with foreign students after a tyre explodes.

Behind the minibus will be a petrol tanker which jackknifes, spilling fuel with other vehicles piling up behind it.

Bill Howkins, a senior divisional officer for West Sussex Fire Brigade, said: "There will be people with head injuries, whiplash, cuts and bruises. It is a major exercise and we want it to be as realistic as possible."

The exercise will involve the Highways Agency and the Environment Agency which will use it to test the tunnel's drainage system.

Michael Dennis, the West Sussex Cabinet member for public s afety, has apologised to road users for any delays and inconvenience.

He said: "It is vitally important we regularly test our procedures and the inconvenience of closing the tunnel for four hours is vastly outweighed by what we hope to learn.

"You cannot put a price on the knowledge which is needed to save human lives."

During Operation Parris there will be diversions for traffic involving Kingston, Old Shoreham Road and the A293 Hangleton Link.