A week after opening, Sydney's newest piece of public transport is already sometimes too crowded for all the people who want to use it.

The tram that runs from Central Station into the inner west was once a boutique line, almost always offering a seat to the relatively few commuters catching it between Lilyfield, Pyrmont and Central.

Chockers: a city-bound light rail at 8.30am on Wednesday morning. Credit:Ben Rushton

But after the extension of the line from Lilyfield to Dulwich Hill opened last Thursday, the trams are filling up so much it can be difficult to fit everybody on.

On Tuesday the driver of at least one morning tram had to ask people to get off and wait for the next service. The crowds were also thick on Wednesday morning, despite limited marketing of the new service.