The crossing, in an industrial part of Williamstown, closes for just 11 minutes in the two-hour morning peak but has been fast-tracked for removal by 2019 as part of the Andrews government's $6 billion level crossing removal project.

The crossing will be removed by building a new rail bridge over Kororoit Creek Road - a miniature "sky rail" in the west.

Residents who attended an information session held by the Level Crossing Removal Authority this week say they were told the line might be shut down for months during removal works.

"They did say that it would be up to two to three months that we would have no train," Jennifer Williams, an Altona Loop Group member who attended the session, said.

"And we would have to use buses. Now that is an awfully long time to have a replacement bus service."

The government said no final decision had been made on how the project would be delivered, including the duration of line shut-downs.

"While there will be impacts as a result of the level crossing removal, no final decisions on the timing and duration of rail and road closures have been made," Jacinta Allan, minister for public transport, said.

"These decisions will be determined through the tender process, and be informed by the planning and community consultation currently under way."

The rail line will also be straightened as part of the works, the Level Crossing Removal Authority said in an information brochure.

A rail bridge has been deemed the likeliest option, to minimise disruption to the nearby Mobil refinery and underground pipelines.

"Initial analysis indicates the most likely solution to remove the boom gates is to build a rail bridge over Kororoit Creek Road," the authority said.

The single track Altona Loop is one of the Metro network's biggest bottlenecks, but will remain a single track after the new rail bridge is built.

Single track sections reduce rail capacity and Altona commuters rely on a sparse rail service of a train every 22 minutes in the peak, and every 20 minutes between peaks.

Passengers were told by Labor that services would improve after the Regional Rail Link opens but a timetable upgrade has been deferred until later this year, despite the link being open since June.

Altona commuters are also among the most frequent victims of station skipping. Metro services occasionally bypass the Altona Loop when there is a disruption, stranding passengers at Laverton or Newport stations. There were 370 Altona Loop bypasses in 2014-15.

There are long-term plans to duplicate the Altona Loop to improve services but no firm commitment or date for when.

Ms Williams lamented that the level crossing removal would not facilitate an improvement to the sparse rail service.

"They're not going to do duplication, so our train service will be the same, pre and post-removal," she said.

The Kororoit Creek Road crossing was ranked 151st on a 2008 Department of Transport priority list for removal.

Kororoit Creek Road is used by about 20,000 vehicles a day and is the main road connection between Williamstown, Altona and the Princes Freeway.