It is alleged that around 1pm a small white tanker carrying pet food waste ran into a small white truck from Victoria carrying water, local Highway Patrol Sergeant Stephen Pidgeon said.

It is believed the water truck was driving slower than the pet food tanker in the left-hand lane heading south, Sergeant Pidgeon said.

The collision caused the tanker to veer off the road and head into bush and scrub on the left-hand side of the highway.

The tanker was majorly impacted at the front and those on scene described it as a lucky escape for the drivers.

Neither drivers sustained serious injuries, although the driver of the tanker had some bruising.

Police won't be pressing any charges, Sergeant Pidgeon said.

Emergency services first thought the water tanker was carrying fuel and firefighters from Fire and Rescue Yass Station 511 and Yass Support Rural Fire Brigade were quickly on scene. However, they left as soon as it was identified there was no threat of fire.

One of the southbound lanes has been closed and is slowing traffic.

Police remain on scene and are waiting on tow trucks to remove the damaged trucks.

"This acts as a timely reminder ahead of the public holidays for people to maintain their vigilance on the road," Sergeant Pidgeon said.

Operation Tortoise, the state's Easter long-weekend road-safety operation, will start at 12.01am on Thursday, April 18 and run until 11.59am on Monday, April 22.

Double demerits will be in place from 12.01am Wednesday, April 24 until 11.59pm on Sunday, April 28 as part of Operation Go Slow across the Anzac Day public holidays.