Three people have been taken to hospital after an accumulation on the M4.
The rescue services were called at 13.35 on Sunday to a collision with several vehicles, which led to the eastbound lane being blocked.
Motorists faced severe delays in London between junctions 4 and 3 near Heathrow Airport.
Emergency services, including National Highways traffic officers, arrived at the scene and the westbound route was blocked to allow the air ambulance to land.
A spokesman for the London Ambulance Service said: “We were called at 1.35pm today (Sunday) for reports of a road traffic collision on the M4.
“We sent a number of resources, including three ambulances, a doctor in a fast emergency vehicle and an operations manager.
“Our crew treated patients on the spot and took three people to the hospital.”