Victoria’s Easter holiday road toll increased to four on Monday afternoon, after a man was killed in a crash north-west of Melbourne.

Police believe the man was driving north along Troups Road South at Mount Cottrell, near Melton, when his car left the road, hit a large boulder and rolled.

The man was the sole occupant of the vehicle. Victoria police are preparing a report for the coroner.

A woman was found dead in a car near Ouyen, in Victoria’s west, by passersby on Monday morning.

It appeared her vehicle had veered off the road and crashed into a tree, but it was unclear when the crash had occurred, police said.

In other deadly crashes at the weekend, a 73-year-old woman was killed and a 79-year-old man suffered life-threatening injuries after their car was allegedly struck head-on by another vehicle overtaking on a bend on the South Gippsland Highway at Lang Lang on Monday morning.

It is believed the couple, from Leongatha, were travelling home at the time.

The female driver of the overtaking vehicle was also seriously injured.

And a male motorcyclist died after crashing into a tree at Baxter, on the Mornington Peninsula, on Saturday night.

Police urged holidaymakers returning to Melbourne late on Monday to slow down and drive safely.

A VicRoads spokesman said nearly all major highways and freeways were congested on Monday night, as hordes of Melburnians made their way home after the long weekend.

Traffic was particularly slow on the Hume Highway southbound between Wallan and Kilmore about 6pm, while there were also delays on the South Gippsland Freeway and Highway due to minor crashes, the spokesman said.

The latest deaths bring Victoria’s provisional road toll to 76, two more than at the same time last year.