Police believe a truck carrying sheep was travelling on Gisborne Road near Darley when the driver lost control about 11.25am.

An Ambulance Victoria spokeswoman said the driver, a 55-year-old Huntly man, was airlifted to hospital in a stable condition.

The front passenger, a 17-year-old Huntly woman, was airlifted to The Alfred in a serious condition also with upper body injuries. Both patients were stable last night.

Police investigations will continue. Anyone with information or with dashcam footage should contact Crime Stoppers.

The crash in Darley comes after a statewide police operation focusing on key causes of road trauma, including drink and drug driving.

Operation Amity took place over the Australia Day weekend and saw police members detect more than 4800 offences.

They included 2649 speeding offences, 371 instances of signs or signals being disobeyed, 299 mobile phone offences, 234 drink drive offences, 179 seatbelt offences and 141 drug drive offences.

Police also found 544 unregistered vehicles being driven, 133 disqualified or suspended drivers and 200 unlicensed drivers behind a wheel. Police also impounded 106 vehicles.

Road Policing Command Assistant Commissioner Libby Murphy said it was disappointing to see people continuing to make poor decisions on the road.

"No one is invincible, and that's unfortunately the hardest lesson people learn," Assistant Commissioner Murphy said. "Until the message sinks in for everyone, we'll continue educating the community and enforcing where possible."

Operation Amity coincided with the National Day of Action which saw police from across the country combine their efforts into enforcing positive driver behaviour and lessening the incidence of trauma on our roads.

Assistant Commissioner Murphy praised those who took the road safety message seriously.

"For each person who looked after their mate and stopped them making a poor decision, or who simply considered their own actions before driving, this is what saves lives," she said.

"I sincerely thank you for the part you have played in road safety."