Unwell driver flips car in Sydney tunnel

A man who flipped his car in the Sydney Harbour Tunnel causing traffic chaos around the city during a wet morning has said he wasn't feeling well, police say.

The accident occurred at about 7.30am on Thursday when a driver in his 50s tried to move left into the breakdown lane.

The man misjudged the move and drove up a safety wall, about 200m from the southern exit, flipping the car onto its roof, police report.

The crash forced the city's centre into near-lockdown during the morning peak, with major traffic jams stretching 10km.

A doctor, in a nearby vehicle, assisted the man until emergency services arrived.

The driver was not seriously injured.

The tunnel was closed until 9am while emergency services removed the car, and minor damage to the wall was repaired.