Motorists in Maidenhead can expect some delays after a crash on the sliproad to join the M4 London-bound.
A silver Ford Transit van and a Ford Saloon were involved in a crash after 5pm between junction 8/9 and junction 10.
Police were notified at 5.28pm. A police spokesman said the accident had caused some damage to the cars and no injuries had been reported.
There are reports of one lane being blocked on the M4.
One motorist who saw the scene of the accident after it had just happened, said: "There is a lot of debris on the road and it looks like one car has gone into the back of another."
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