Roadworks expected to cause major delays on Melbourne's West Gate Bridge

Victorian motorists are being warned to brace for extreme traffic delays over the next two weeks, with road works to take place on one of the state's most critical thoroughfares.

Three of five citybound lanes on the West Gate Bridge will close from 9pm tonight until the evening of January 4.

The Department of Transport has warned there will be significant delays for motorists heading into the city due to annual maintenance works.

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Last year the same bridge works sparked nightmare delays.

"Motorists are advised to plan ahead and allow extra time for their journey, with only two citybound lane open during this period," a spokesperson from the department said.

"Delays of up to 30 minutes are expected."

People travelling to the city from the western suburbs for work, shopping or to attend events are strongly encouraged to use public transport.

The works will replace the waterproofing membrane on a section of the bridge as well as resurfacing and line marking.