Police are investigating the death of a motorcyclist who hit a traffic light at Ovingham in Adelaide’s inner north overnight.

The man’s death came after another rider sustained life-threatening injuries on Thursday, and a driver died in hospital following a separate collision at Nuriootpa on Monday.

Emergency services were this morning called to Ovingham about 2:30am following reports “a Harley Davidson motorcycle had collided with a traffic light”, police said.

The 40-year-old rider, from Para Hills West, died at the scene at the intersection of Park Terrace and Torrens Road, and Major Crash investigators are examining the circumstances of the incident.

Yesterday, a 50-year-old Naracoorte man was flown to hospital with life-threatening injuries following a separate motorbike crash on Bower Boundary Road at Brownlow near Eudunda north of Adelaide.

Police this week appealed to drivers ahead of Easter, citing last week’s fatal crash near Birdwood in which three people were killed.

“That investigation is ongoing and once we fully understand the exact circumstances of what happened in that case, that’ll progress in relation to an outcome,” Superintendent Shane Johnson, officer in charge of the SA Police Traffic Services Branch, said on Wednesday.

The scene of an Adelaide Hills crash involving a truck and a car.

Three people died last week in a crash near Birdwood. (ABC News)

Superintendent Johnson said police were conducting three road safety operations during the long weekend.

“We’ll be targeting drivers who speed, drivers who drive distracted, drivers who drink and drug drive, and drivers who are driving dangerously and taking risks on our roads,” he said.

“We know that even a few kilometres over the speed limit can have devastating consequences.

“Twenty-five per cent of lives-lost collisions this year have been attributed to speed.”

On Monday, a crash between a truck and a ute at Nuriootpa left three occupants of the ute — a 47-year-old Greenock man, a five-year-old boy and a three-year-old girl —  with serious injuries.

Police today confirmed the man had since died in hospital.

The truck driver suffered only minor injuries, despite the truck catching fire at the scene, at the intersection of the Sturt Highway and Old Kapunda Road.

This week, a pedestrian was killed when she was hit by a bus in Adelaide’s CBD.

Police said the 39-year-old North Adelaide woman could have been retrieving something from the road when she was fatally struck.