It is believed the vehicle left Portland-Nelson Road, a Victoria Police spokeswoman said.

The male driver, who is yet to be identified, has died at the scene. The exact cause of the crash is being investigated.

Victoria's road toll now stands at 122, compared to 105 at the same time last year.

Anyone who may have information is urged to contact Crime Stoppers on 1800 333 000 or file a confidential report at www.crimestoppersvic.com.au.