Sydneysiders may take some small comfort in the fact that it is not just their train route that is overcrowded during the morning peak, almost all of them are, new data has revealed.

The Bureau of Transport Statistics considers trains operating at 135 per cent of capacity to be "uncomfortable" and "behind schedule".

But dozens of peak hour trains are running at well over 135 per cent capacity, with one — the Northern Line from Hornsby — reaching 180 per cent.

The Western and Illawarra lines are above 170 per cent.

On average, five of the 14 CBD lines are over capacity in the morning peak (between 8-8:59am), but they are all below the 135 per cent threshold in the afternoon peak (from 5-5:59pm).

All the intercity lines — the Blue Mountains, Newcastle and Central Coast, and South Coast — were under capacity in both the morning and afternoon peak.

Government needs to act 'super quick'

Transport Minister Andrew Constance said the increase in commuters was unprecedented.

"Over the last 12 months it's off the charts in terms of increased patronage," he said.

"The Government is going to have to act super quick.

"We are going to have to acquire new trains very, very quickly in order to cater for the growth that we've seen."

Mr Constance said the Government was working on easing congestion.

"We're going to see the first Metro train in 2019 — Metro North West," he said.

"We are doing everything we can to deliver that as quickly as possible. In the meantime were are going to deliver more trains, more services."

Opposition transport spokeswoman Jodi McKay has called on the Government to outline a plan for the overloading of trains.

"The Government needs to look at signalling, it need to look at what capacity is on the Western Line in particular," Ms McKay said.

"We know that right across the network there is congestion, now we've said this to the Government, they know this.

"But they are moving too slowly to fix this."

Ms McKay also asked for more clarity around the newly announced Metro lines.

"At the moment we have two conflicting plans that are on the table — we want to know how those are going to work together and how it's going to ease congestion on the Western Line," she said.