The decision has met opposition among ACT RFS brigades, which say it forced crews to wait in traffic on the way to fires, potentially slowing response time.

ACT RFS chief officer Joe Murphy said he made the decision for safety reasons.

The territory's RFS members were not trained to drive under lights and sirens, or "urgent duty driving" in which regular road rules can be ignored, Mr Murphy said.

"Urgent duty driving is a dangerous undertaking, and ACT Emergency Services Agency need to consider firefighter and community safety," he said.

The restriction stayed unchanged in last weekend's extreme conditions, when temperatures hit a record high of 44 degrees for Canberra and the territory was in a state of alert.

In contrast to the ACT's rural fire service, NSW RFS vehicles were able to pass through the territory on Saturday while driving under lights and sirens when responding to fires in southern NSW.

The ban has frustrated ACT RFS brigades, said a source familiar with the situation who did not want to be named.

"Not only does this mean a slower response time, it means that vehicles on the road are not aware that the RFS is heading to an incident and can't move out of the way," the source said.

ACT RFS strike teams had been unable to respond using lights and sirens when called to urgent duty in surrounding fires in NSW, the source said.

Mr Murphy said the Emergency Services Agency was not aware of any recent incident when ACT RFS crews were delayed by traffic when responding to fires.

"Strike teams were deployed as requested by NSW RFS, and travel in convoy under normal road rules," Mr Murphy said.

"There have been no concerns reported by ACT RFS members about delayed response times."

More than one ACT RFS tanker responded to grass and bushfires in the territory, typically from different locations, Mr Murphy said.

"This is a contingency to allow for potential traffic congestion in one area."

The suburban-based ACT Fire & Rescue, which trained its members in urgent duty driving, supported ACT RFS in responding to grass and bushfires, Mr Murphy said.

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The standing order not to use lights and sirens marked a change in ACT RFS policy starting in September.

"The direction was to address the fact that ACT RFS do not and have not provided urgent duty driving training to members, and there is no currency of skill maintained", posing greater and future risks, the chief officer said.

The Emergency Services Agency and ACT RFS were committed to giving the training needed to reintroduce urgent duty driving, Mr Murphy said.

Both organisations had discussed the issue of urgent duty driving with brigade captains and presidents, he said.

For the ACT RFS brigades, the issue was trust, the source said.

While rural firefighter crews were trusted to manage a fire once they arrived, they weren't trusted to use their experience and judgment to drive under lights and sirens, the source said.