A motorist crashed into a barrier on a Cape Town highway after his vehicle was stoned.

The man was driving along the N2 highway near the Cape Town International Airport on Thursday when his car was hit.

Western Cape emergency health services spokeswoman Keri Davids said the unidentified man was taken to hospital.

A passing motorist Ray Wright said he was driving from the airport after 2pm when he saw two men on an overhead bridge holding a rock and dropping it on the freeway.

"It hit a white car and it skidded all over the road before crashing into the barrier. The car got hit quite hard by the rock," Wright was quoted as saying.

"I could not see what happened to the driver but he hit so bad on the barrier I don't think he is still alive."

He stopped to check but a group of men emerged from the bush and started attacking a delivery truck.

The truck driver escaped unharmed.

Wright said he tried phoning police but could not get through.

According to the report, two delivery trucks were stoned and set alight in the vicinity on Thursday, amidst wage talks in the transport sector.

Provincial traffic chief Kenny Africa said the strike stoning reports could not be linked to the accident involving the white car.