A roadsweeper vehicle was hit by a Transit van causing it to flip on its side. The council roadsweeper was travelling down Harwood Lane in Great Harwood at 10.20am on Friday when the crash happened.
Police said the van ran into the back of the roadsweeper after coming round a sharp corner on the 60mph road.
The collision caused the transit van to career off the road into a grass verge which caused significant damage to the front end of the vehicle.
Nine firefighters from Hyndburn Fire Station spent half an hour cutting the 39-year-old van driver out of the vehicle using hydraulic cutters.
He was taken to Royal Blackburn Hospital with suspected spinal injuries and also lost some of his teeth in the crash.
The 41-year-old roadsweeper was also taken by ambulance to hospital with back injuries.
Accident investigators attended the scene on Blackburn Old Road for around four hours and the road was closed from the junction with Wilpshire Road to the junction with Goldacre Lane.
A police spokesperson said: "An investigation into the road traffic collision is being carried out to look into the circumstances of the accident. No arrest have been made."