A DRIVER spotted attempting to join the M4 down an exit ramp caused traffic chaos this afternoon.

Wiltshire Police were alerted to the car on the slip road at junction 17 near Royal Wootton Bassett by a member of the public at 2.30pm.

“The risk of a serious accident was very high, so police and Highways Agency made emergency efforts to slow the traffic using a rolling roadblock and setting the matrices to 20mph,” said the force in a statement.

“The vehicle was never located, it is possible that the driver realised their mistake and turned their vehicle around, thankfully without incident.”