A serious car and motorbike accident at the Sydney Harbour Bridge is causing a huge traffic jam.

This incident has lead to the 12-kilometer-long traffic jam for the commuters trying to cross the bridge. The crash occurred just before 6 a.m. on Wednesday opposite Milsons Point Station.

All lanes across the Sydney Harbour Bridge reopened at about 8:15 a.m. but motorists are still advised to stay away, a Transport Management Centre spokesperson told Sky News.

Motorists travelling from the north have been advised to use the Anzac Bridge and Victoria Road.

Three city-bound lanes and one northbound lane were closed because of the accident opposite Milsons Point Station.

A Crash Investigation Unit is currently on the scene to examine the crash site.

Buses are experiencing the delays of about 45 to 60 minutes.Passengers are told to board the train in order to reach their desired destinations.

All lanes have now been reopened, but major delays are still affecting the area, a spokesperson for Transport Management Centre confirmed.

“Southbound traffic approaching the bridge is queued 12k kilometres, back to the start of the M2,” she said to 9NEWS.com.au

An NSW Ambulance spokesperson said the motorcycle rider, believed to be a man in his 30s, was taken to hospital with a suspected fractured leg.

The 25-year-old female driver of the Volkswagen car was not injured, and is assisting police with their inquiries, according to Sydney Morning Herald.

In an effort to help solve Sydney’s traffic issues, the Baird government is pushing ahead with the $16.8 billion WestConnex motorway project. SMH reports

An updated business case for Australia’s largest motorway project is due shortly, and will take into account additions such as a western crossing of Sydney Harbour.

The company building Australia’s largest transport project said it needed additional funding from private investors, which two sources said would amount to more than A$1.5 billion ($1.1 billion).