South-west police road safety adviser Senior Sergeant Chris Asenjo said the prime mover hauling two trailers of wood chips was travelling along the Macarthur-Penshurst Road when the driver approached a bend and lost control just before 5.30pm Thursday at Warrabkook, near Macarthur.

"The driver has failed to negotiate the bend, the combination has tipped over, spilling the load and trapping the driver," he said.

"The driver has unfortunately died following the incident.

"The single-vehicle collision is under investigation but initial inquiries indicate the heavy vehicle was towing a significant load, approached the bend too fast and the driver was not wearing a seatbelt."

Senior Sergeant Asenjo said drivers risked their lives when they involved themselves with any of five key major causes of fatal accidents - speed, seatbelts, impaired driving (alcohol and/or drugs), distraction and fatigue.

"Like we've said before, if you mix any of those five factors your life is at considerable risk," he said.

"Drivers need to really take notice of speed advisory signs when towing a trailer, caravan or when operating a heavy vehicle.

"Drivers need to be aware of road conditions, bends and other road hazards.

"There's a very fine line between a vehicle remaining upright and tipping over - it can be just a couple of kilometres an hour."

There have been four fatal road fatalities in the south-west during the past 14 days - at Macarthur, Noorat, Allansford and Woorndoo.

"We're staring down the barrel of six fatalities in two weeks. That's half of last year's south-west road toll in a fortnight," Senior Sergeant Asenjo said.

"Two people have also been transported to Melbourne hospitals in critical conditions, a cyclist involved in a collision with a four-wheel drive at Dennington last Saturday night, and Melbourne woman in her 20s who collided with a tree on the outskirts of Hamilton earlier this week."

Last year's south-west road toll was 12 while 10 people died on the region's roads in 2018.

"We had a shocking start to last year with five people dying on our roads during January and February and a sixth before the end of March," the road safety adviser said.

"Emergency services personnel are the people turning up to these collisions. We're the ones left to pick up the pieces of wrecked lives.

"And there have been other collisions where people have been seriously injured. Those people are in hospital and may never work again - their lives will be changed forever."

Senior Sergeant Asenjo said drivers needed to give due care and attention to controlling their vehicles.

"People are dying in our community. The fix is pretty simple - people need to consider the risks involved in their driving behaviour," he said.

"If you remove those risk factors you have a far greater chance of avoiding a collision and getting home safely," he said.

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