Transport Canberra deputy director-general Duncan Edghill even emailed staff a photo of an empty office as part of a missive to work longer hours.

With the rail system due to start taking passengers in less than 20 days, staff have been urged to do hours outside those set out in their enterprise bargaining agreement to prepare for the launch.

Mr Edghill told staff while he understood they had obligations outside work and he trusted them to "manage their time accordingly", they needed to put in "a little extra desk time now" in order to avoid being "overburdened" in the lead-up to the launch.

He said the directive was "certainly not an instruction" but said past experience on the project had shown staff needed to "pace [themselves] towards the finish line".

The email was sent about 7.45pm on a Wednesday night, and was accompanied by a photo of the empty office.

According to the ACT Public Service enterprise agreement, non-shift workers must work their ordinary daily hours within the span of 7am to 7pm Monday to Friday.

That span of hours may be varied by an agreement between the manager or supervisor and a majority of staff in the workplace.

The agreement also states that managers, supervisors and employees have a responsibility to minimise the extent to which excessive hours are worked.

"While it is acknowledged that peak workload periods may necessitate some extra hours being worked by some employees, this should be regarded as the exception rather than the rule," the agreements says.

"In the circumstances where work pressures result in the employee being required to work, or is likely to work, excessive hours over a significant period, the manager, supervisor and employee together must review workloads and priorities and determine appropriate strategies to address the situation, including re-allocation of resources or considering time off in lieu or other recompense."

Asked about the email and photo, a Transport Canberra spokesman said it was not uncommon for senior leadership members to "encourage" public service teams to deliver on their commitments.

"The project has involved an incredible amount of effort being put in by the ACT government team over many years. In particular, a significant amount of effort is needed when large milestones approach," he said.

"There are still tasks to be finalised, including reviewing documentation from Canberra Metro, the preparation of internal reports and preparing for launch activities.

"The work will culminate in the launch of stage one of the light rail network in April. This requires significant coordination, as is the case for any major event, especially one of this scale."

He said staff had been "exceptionally dedicated and hard-working" throughout the project and had worked late nights and weekends at "key times".

Depending upon the staff member's particular circumstances and discussions with managers, staff are generally entitled to overtime or flex time, he said.

"The government is expecting significant public interest in the launch of light rail. We believe the Canberra community rightfully expects us to have the project delivered safely and as soon as possible," the spokesman said.