A car smashed into traffic lights in Talbot Road in Blackpool town centre, close to the Ramsden Arms pub, police said.
The accident happened at around 12.15pm, with the road closed as a result.
In the initial 999 call police were told the car, described by a witness as a dark Citroen C4, had collided with a motorbike, but the force have since said no bike was involved.
The car's driver is now understood to have fallen ill behind the wheel.
Motorists were being diverted round the back of the nearby Sainsbury's supermarket via Whiteside Street, a police spokeswoman added.
Paramedics were called to the scene and took the driver to hospital, but no information on injuries was immediately available.
Blackpool Transport said its bus services five, seven, nine, and 14 were being diverted via Caunce Street,Grovenor Street, and Cookson street, and said the road is expected to be shut for "at least two hours."
One witness said he saw the driver "on the floor with paramedics rushing to her, with the car smashed in at front and the traffic light on the ground."