A crash involving a Royal Mail lorry in Braywick Road, Maidenhead, caused traffic delays this morning.
Firefighters, police and the ambulance service were called to the scene at about 6am.
Maidenhead White Watch crew manager Marcus Lewis said it appeared that the lorry was coming from the motorway down the slip road towards the Braywick Road carried on to the roundabout and went down the ditch into the roundabout's central island.
Firefighters had to free the driver, a man in his 50s, whose legs were trapped.
He said: "We used cutting equipment and a ram to cut the doors off and ram the dashboard back and get the driver onto a medical board and taken away by ambulance.
"He had leg injuries, I don't know how serious."
Fire crews from Maidenhead and Windsor and a heavy rescue unit went to the crash and were there for nearly two hours.
A police spokesman said recovery of the lorry is estimated to take place at about 10am and 'may cause some delays'.
The injured driver was taken to Wexham Park Hospital by ambulance.