Two motorbike riders who died after crashing head-on at Lonsdale in Adelaide's south on Friday night had no lights on their vehicles, police say.
A 24-year-old man from Aberfoyle Park and a 33-year-old man from Happy Valley died after their trail bikes collided in the dark.
Police believe one man was riding on the road and the other on a dirt track before they crossed paths.
The only light was from the mining helmets on the men's heads.
The pair was found dead at the scene near their badly-damaged bikes about 12:45am.
Friends and family of the victims gathered at the site following the crash.
Inspector Andrew Thiele says a passing driver came across the scene.
"She saw some debris on the road, she went to drive around the debris and as she drove around she saw the bodies," he said.
"Despite constant community education programs, despite constant community messages... these men were undertaking dangerous riding practices, they were riding un-roadworthy bikes, there was no lighting, they didn't have any helmets on and it was just a tragedy waiting to happen.
"Last year it took us until the eighth of January to have our first fatality. We appeal to the community: road deaths are not inevitable."