Thirteen people have been killed on South Australian roads so far this year — making it the second-worst start to the year in a decade.
The road toll was four at this time last year.
Assistant SA Police Commissioner Ian Parrott said distraction, including fatigue, had been responsible for at least five of the deaths.
He said police were investigating whether dangerous driving played a part in four of the crashes, whether excessive speed was involved in two and whether alcohol was a factor in one.
"They are absolutely preventable — there's a senseless loss of life on South Australian roads because these crashes are preventable," he said.
"People are speeding, people are letting themselves be deliberately distracted when they're driving, people are drinking before they drive and people are unbelievably not wearing their seatbelts while they drive."
Mr Parrott said police were "imploring everybody to do the right thing on the roads".
"The thing that concerns us the most is, that of the deaths that have happened so far this year, the drivers are the people who have died and our initial investigations indicate that they are largely at fault for their own demise," Mr Parrott said.
"What is the message that people are not getting here?
"This has to stop, and it has to stop now."
Four fatal crashes this week
This week has been particularly horrific in terms of lives lost on South Australian roads.
The most recent crash happened just before 11am today when a driver crashed a Toyota station wagon into a tree at the intersection of Irwine Street and Heritage Drive at Wallaroo.
The 48-year-old North Beach man died at the scene.
On Monday, an 18-year-old man from Naracoorte died when he crashed his car into a tree on the Riddoch Highway near Johnstons Road at Keppoch in the state's south-east.
On Tuesday, a 25-year-old local woman rolled her car on Port Wakefield Road and died the next day in hospital.
Last night, a 27-year-old from Leasingham in the mid-north was killed when his car crashed into a tree at Shea-Oak Log, north of Adelaide.
Major Crash officers have examined the scene and police are continuing to investigate the circumstances of the crash.
Earlier on Thursday, a 79-year-old ACT woman suffered critical injuries when the car she was driving collided with a truck at Two Wells.
The crash happened on the Port Wakefield Highway near Brooks Road, and emergency services were called to the scene just after 2pm.
The driver of the car remains in the Royal Adelaide Hospital in a critical condition, while a passenger — an 80-year-old Victorian woman — was taken to the Lyell McEwin Hospital with serious but non-life-threatening injuries.
