A 17-year-old boy died in Whitehorse General Hospital last night after driving his all-terrain vehicle through a stop sign and into the side of a truck.

Chase Savoie, a resident of the Marsh Lake area near where the collision occurred, wasn't wearing a helmet at the time, said Const. Paul Thalhofer, an RCMP crash reconstructionist who was called to the scene Monday evening.

The 17-year-old was riding a 1984 Honda three-wheeler when he drove up the South McClintock subdivision access road just south of the McClintock River Bridge onto the Alaska Highway.

The southbound Suburban towing a camper trailer was on a long straight-stretch when the ATV drove into the side of it at about 6 p.m., said Thalhofer.

An ambulance crew was the first of the emergency personnel on the scene. The young man was taken to the hospital, where he later died from his injuries.

Savoie died from massive head injuries, injuries Thalhofer believes would have been considerably less if he'd been wearing his helmet.

'That was a major factor in the degree of the injuries,' Thalhofer said, though he added he doesn't know if the young man would have lived if he'd pulled on the helmet.

'Had he been wearing a helmet, it would have lessened the degree of injuries.'

With this as the second fatal incident in two days involving Yukoners out enjoying the summer weather, the RCMP are sounding the reminder to take the safety precautions necessary to enjoy the outdoors safely.

The young man would have had nearly 70 metres of clear sight-line on the access road before he came to the stop sign, the constable said.

'There was no reason for him not to see the stop sign,' said Thalhofer.

The ATV is being examined today to determine if there were any mechanical problems such as brake failure that led the 17-year-old to go right through the marked stop sign.

The mechanical inspection is the last part of the traffic analyst's investigation before he writes up a report for the Yukon coroner's office.

Alcohol is not believed to be a factor in the collision.

After striking the Suburban carrying a Whitehorse family on their way Outside, the three-wheeler spun and hit the trailer before rolling several times. It came to a rest on the Alaska Highway.

Two witnesses estimated the Suburban driver was travelling at about 90 kilometres per hour in the 100 km/h zone.

The teen had been riding alone.

Thalhofer said marks on the road left behind after the crash didn't allow him to calculate speeds for the Suburban and ATV.

A tourist called police about the crash at 6:02 p.m. Passersby stopped after the crash to lend a hand.

Three-wheeled ATVs haven't been manufactured in years after they were found to be too unstable, Thalhofer said.