A 16-year-old boy has died after crashing his motorcycle in Adelaide's northern suburbs over the weekend, in what has been a horror week on South Australian roads.

Key points: There have been six deaths since Thursday on South Australian roads

There have been six deaths since Thursday on South Australian roads The deaths include a passenger from a collision on Thursday morning

The deaths include a passenger from a collision on Thursday morning There were two serious crashes this morning involving trees

The boy, from Parafield Gardens, was rushed to the Royal Adelaide Hospital in a critical condition on Saturday night after his blue Honda motorcycle hit a stobie pole in Pooraka.

He died from his injuries overnight.

Major Crash Investigators are appealing to the rider of a blue Kawasaki motorcycle that was travelling west on Maxwell Road at the same time as the boy to contact police, as he may be able to assist in the investigation.

They are also calling for any other witnesses to come forward.

The boy was one of multiple deaths on South Australian roads over the weekend.

Just before 11:00am on Sunday, emergency services were called to a crash at Nepabunna, near Leigh Creek, in the state's far north.

A 57-year-old local man, who was the driver and sole occupant of the station wagon, was found dead at the scene.

A passenger involved in a crash last week near Port Wakefield, also died over the weekend from his injuries.

Just before 10:30am on Thursday, emergency services were called to the intersection of the Copper Coast and Augusta Highways after a crash between a car and a truck.

A passenger has died following a crash at the intersection of the Augusta and Copper Coast highways last week. ( ABC News )

The driver of the car, a 72-year-old woman from Henley Beach South, died at the scene.

Her passenger, an 82-year-old man, also from Henley Beach South, died at the Royal Adelaide Hospital from his injuries on Sunday morning.

The driver of the truck was not injured.

Fatal crashes at Hindmarsh Valley and Kudla

A woman also died this morning following a crash at Hindmarsh Valley, when her car struck a tree.

A man died in another similar crash at Kudla, north of Adelaide, this morning.

About 7:10am, emergency services were called to Dalkeith Road, near Stebonheath Road, where a car had crashed into a tree and burst into flames.

The dead man was the only person in the car and police believe that speed was a factor.

A man died when his car crashed into a tree at Kudla. ( ABC News: Helen Frost )

'We need to stop this carnage'

The state's road toll is 96, compared to 63 at the same time last year.

Police described the mounting road toll as unacceptable.

"If six people got murdered in the state of South Australia in the last five days, can you imagine the community outrage?" Superintendent Bob Gray asked.

"There just seems to be this total lack of concern and empathy within South Australia and we need to take responsibility for our behaviour on the roads and we need to stop this carnage."

"People need to understand the devastation that six families are feeling as a result of what's occurred since Thursday. It's not just simply a number, and there should be no toll for using our roads."

Superintendent Gray said that he believed more than 40 per cent of fatalities this year were as a direct result of inattention.

"Probably about 17 per cent of fatalities as a direct result of people behaving recklessly on the road," he said.

"Unfortunately, my people have to attend the scene, as do other emergency services and passers-by. And they have to deal with what's left that is the families, and the communities and the people that are broken. And some people never recover from this."