A local delivery truck driver stunned even the most seasoned police and medical professionals on Tuesday when a breathalyzer test revealed a blood-alcohol level more than five times the legal limit.

"That's way up there. You don't get much higher than that. Those levels would usually kill someone," said Dr. Robert Baker, an addictions medical professional based in Kamloops.

But not only was the 42-year-old Kamloops man still alive, he was driving a five-tonne cube truck.

He came to the attention of police at around 3:45 p.m. Tuesday when a witness noticed the truck bearing the name of a nearby business rolling unoccupied through a parking lot in the 800 block of Notre Dame while a man staggered towards it. The driver eventually caught up, got in and took off.

Police were a minute away when a call came in of a rear-ender at the corner Notre Dame Drive and Summit Drive.

A woman in a 1996 Acura Integra had been in the right hand lane waiting to turn onto Summit Drive when the truck driver plowed into her.

Other than a stiff neck and back, the woman was uninjured.

The driver was taken to the RCMP detachment where a test indicated a blood alcohol level of 0.42 per cent, according to police.

He was held until sober "and could care for himself," said RCMP Staff Sgt. Grant Learned, and was released on a promise to appear to face charges of drunk driving.

The severity of his drunkenness wouldn't affect his charges, said Learned.

Learned assured media that the breathalyzer result was accurate but he understood any incredulity.

"Like he should be dead? Yeah," he said.

Baker said 0.42 per cent could be in the top 10 per cent of blood alcohol levels ever recorded.

The fact that the man could still function shows he drinks copious amounts on a daily basis.

"The more alcohol you drink the more your body tries to resist it and the more enzymes it will develop in your liver to break down alcohol," he said.

In most other people, that level of alcohol would lead to death because just as the brain forgets simple tasks like speaking when drunk, extreme inebriation can lead the body to forget life-sustaining activities like breathing, said Baker.

British pop star Amy Winehouse registered more than five times the legal limit of alcohol in her system when she was found dead due to alcohol intoxication in her apartment in July 2011.