Rocks and mud were thrown from a railway bridge and hit a car which was travelling on the road beneath.
Police are appealing for witnesses after the incident in Epsom Road North in Tadworth, Surrey.
The green Vauxhall Corsa, being driven by a 22-year-old man, was badly damaged by the stones and rocks.
The man, who was driving home from a night in Kingston in the early hours of the morning, said he felt lucky he did not have a serious accident.
'Reckless behaviour'
At least £1,000 damage was caused to the car after the rocks dented and scratched the roof, wing and bonnet and smashed a headlight.
It is believed youths were responsible for throwing the rocks, the latest in a series of incidents where items have been thrown from bridges onto traffic.
In one incident in March a lorry driver was killed when a brick was thrown through his windscreen.
Pc Helen Rickshaw said: "We are treating this incident very seriously.
"The reckless behaviour of whoever is responsible could easily have resulted in a nasty accident on the road below.
"I cannot believe that anyone thinks that throwing objects at a moving vehicle is just a laugh, especially after the death of the lorry driver on the M3 after a brick was thrown through the his windscreen earlier this year."