Drivers are being advised that the B488 between Horton and Ivinghoe is closed at the canal due to damage on the bridge.
The bridge was hit by a vehicle at about 2am on Monday morning, Thames Valley Police were at the scene and Transport for Buckinghamshire have since taken over and checked the full extent of damage to the bridge.
A spokesman for the Canal River Trust, who own the bridge, said: “The vehicle has damaged the whole parapet of the bridge and the driver had to go to hospital.
“Our team has been onsite today trying to make the bridge safe and the police have closed the road off.”
A Transport for Buckinghamshire spokesperson said: “The bridge damaged in the crash on the B488 between Horton and Ivinghoe belongs to the Canal and River Trust.
“The crash resulted in damage to the bridge parapet and has rendered the bridge unsafe for vehicular traffic at this moment in time.
“As a consequence the bridge has been closed and a diversion route has been sign posted via Cheddington.
“TfB’s engineers will be working with the Canal and River Trust to ensure that the road is opened to traffic as soon as possible.”
Drivers will be able to follow a diversion route via Cheddington.