Until Tuesday, testing had only been done on the section between Gungahlin and Antill and Mouat streets. It's now heading to the Alinga Street terminal, in the first day of final tests.

It is unclear how long this last testing will continue, though Transport Canberra deputy director-general Duncan Edghill told ABC Radio there was now some doubt as to whether operations would begin in early April.

If testing is further delayed, it may delay the government's plans to have a new bus network operating from early April, putting parents of school children particularly in doubt as to the long-term schedule for public transport.

The start date has been repeatedly delayed over the past 12 months, though the tests of vehicles on the track beginning on Tuesday represents the final phase of testing before passengers can actually begin using the long-awaited service.

The testing will include some night-time tests after 9pm and before 5am, though initially trams will travel at low speeds, building up to the 70km/h speeds it will operate at.

Mr Edghill said while he hoped it would be operating by the end of April, he could not guarantee it, given third party certification was needed, but he would not 'put the house on' an April start date, he told ABC Radio.

Asked when it would start operating, a Transport Canberra spokesman said it was expected to start from April 27, along with the new integrated bus network, but he would not answer questions regarding when testing would finish.

Testing of the final leg of stage one, from Flemington Road to Civic, is expected to continue for weeks as Canberra Metro looks to ensure it meets technical and safety standards, but the consortium and government have refused to put a completion date on it.

"Light rail vehicles have now travelled under their own power to Dickson," the directorate spokesman said.

"They are currently expected to travel all the way to Alinga St by mid-February."

Transport Minister Meegan Fitzharris has encouraged all users of the light rail corridor to stay alert throughout testing. They should take particular care around traffic intersections, not run red lights and pay attention to any traffic control workers' directions.

She said the trams were quiet and took longer to stop than other road vehicles. She urged drivers not to queue across intersections and wait for the path to be clear before driving across the tracks.

"Traffic light patterns at intersections are changing as the light rail integrates with the road network," she said.

Workers on the track were also clearing debris, largely dirt and leaf litter from the track during testing on Tuesday, but the directorate sopkesman said that was largely due to vehicles not previously being tested on that section of the track.

Vehicles have previously been tested on that section of the track, though not at such a technical level.

The spokesman said the track would be periodically cleaned for debris once it was operating, but it was expected wind from the passing vehicles would clear most of the debris.