Eight-mile queues have gathered on the M62 after "medical episode" led to the road being shut.
Both carriageways were closed - but have since re-opened - as an air ambulance landed on the motorway at junction 20 near Rochdale around an hour ago, police said.
A car crashed into the central reservation and the driver needed to be taken to hospital.
There are still long delays between junction 15 and 20, according to Highways England.
A Greater Manchetser Police spokeswoman said: "At around 4.10pm police were called to junciton 20 of the M62 to a report that a car had gone into the central reservation.
"The driver was taken by air ambulance to hospital for treatment."
North West Motorway Police tweeted: "Patrols dealing with a medical episode J20 M62...both cways being closed to assist Helimed....hopefully get you moving soon."
But Highways England said there were approximately eight miles of queues.
In a statement, the agency also said: "The M62 in Greater Manchester is experiencing long delays in both directions between J22 and J21 following an incident. The Air Ambulance has attended and North West Motorway Police Group have now re-opened all lanes in both directions but long delays remain which should start to ease shortly."
It is understood the incident occurred on the westbound carriageway but the ambulance landed on the eastbound carriageway.