SYDNEY suffered a major day of transport chaos after a massive pile-up on the Harbour Bridge caused traffic chaos and the rail network suffered massive delays after a man tragically died on train tracks.

The Sydney Harbour Bridge has now reopened after a major smash involving a empty petrol tanker and several cars caused lane closures around lunchtime.

A CareFlight helicopter took a woman who had been trapped in her car to hospital.

She was unconscious and had suffered a head injury. Fairfax websites reported that she was in a critical condition.

Emergency services treated three other people, two of whom were a serious condition.

All northbound lanes were closed and a water main burst as a result of the collision.



Motorists are urged to avoid the area Sydney Harbour tunnel, and expect significant delays and consider alternate routes.



Buses that cross the Harbour Bridge have now returned to their normal routes but there are extensive delays to services.



Trains are operating across the Sydney Harbour Bridge with no delays.

Meanwhile train services are starting to return to normal after a man who was tasered by police after stabbing himself in the neck died on the railway tracks at Central Station.



Emergency services were called to the country platforms of the station about 12.50pm (AEDT) today, following reports a man was threatening to harm himself with a knife.



Witnesses told police the man went onto the railway tracks and started walking towards Redfern.



Police also entered the rail corridor and tried to restrain the man, but he stabbed himself before police used a Taser on him.

Tragically, despite efforts by emergency services to save him, the man died at the scene.



* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14