But the three hours that 160 passengers spent trapped inside a train midway between Hallam and Dandenong on Tuesday was, the chief executive of Metro Trains concedes, excessive.

An overhead wire in Dandenong broke and came down on top of a running Metro train early in the morning, taking out rail services for the outer south-east during rush hour.

Metro Trains passengers were left frustrated, but were at least able to catch a bus.

Less fortunate were the 160 passengers aboard the 4.36am V/Line service from Traralgon.

Stuck between Hallam and Dandenong stations, they had expected to arrive at Flinders Street Station about two hours after they left Traralgon.

"They got in [to the CBD] about 11am," Metro Trains chief executive Andrew Lezala said at a press conference on Tuesday afternoon after he was called upon to explain what had happened.

Among the V/Line commuters was Andrew Winsall, who boarded at Pakenham just before 6am. Three hours later, he was still sitting on the train between Hallam and Dandenong. "Love ya work Metro," he posted on social media.

Mr Winsall later told Fairfax Media that he was stuck on the train so long his boss had "told me to not bother coming into work". He said it could mean he would lose a day's pay.

The V/Line passengers, Mr Lezala conceded, had been caught in the middle of a problem of Metro's creation.

Mr Lezala explained that, after the overhead wire came down, power to the train affected was automatically cut.

He said Metro had to instigate a procedure called "wrong line running", to reverse two trains - the V/Line service and another Metro train caught in the breakdown.

To keep everyone safe, including car drivers at a level crossing affected by the wire collapse, the operation had to be done with extreme care, Mr Lezala said.

The latest maintenance issue for Metro Trains comes at an unfortunate time - as it prepares its bid to run the rail network for another seven years to the Andrews government.

The rail operator's contract expires in November next year, and Metro will hand its offer to Public Transport Minister Jacinta Allan by the end of this year.

A spokesman for Public Transport Victoria, John Lindsay, said that, if "appropriate terms" could not be reached with Metro, the "government may pursue alternative options".

The union representing rail workers said a lack of proper maintenance had led its members to call for a return of the previous train operator, Connex.

"There are sections of track that require urgent maintenance," said Rail Tram and Bus Union state secretary Luba Grigorovitch​.

She said instead of fixing the problem, Metro routinely applied speed restrictions to avoid maintenance as long as possible.

"The government and the public would be mortified if they knew how often these cost-cutting measures were occurring," she said.

But Mr Lezala said, in Tuesday's case in Dandenong, ageing infrastructure was not the issue. The overhead wire that had broken was "not particularly old. We have been upgrading the overhead system".

And he said that, under Metro, overall performance had improved immensely since it took over from Connex in 2009.

Ms Allan held a press conference on Tuesday morning - while the 160 V/Line passengers were trapped in Dandenong - to announce improvements the government was making to V/Line .

Asked about these passengers, she said there had been "some challenges getting some passengers off" amid concerns over live electrical wires.

The passengers aboard the V/Line service could have avoided the three-hour hold up had they alighted at Pakenham - as proposed by a public consultation group set up by Infrastructure Victoria.

It recommended creating a "Gippsland/Pakenham rail shuttle" in order to ease congestion on city trains.

Ms Allan on Tuesday poured scorn on the idea, saying Infrastructure Victoria's "Citizen Jury" process that had devised the idea "didn't even have a representative or someone who came from Gippsland".

"This is certainly not part of the government's thinking on how we want to deliver improved services," she said.