A man has died and another been critically injured after the shopping trolley they were riding crashed into a car as they reached 80 miles per hour in Sydney.

The unnamed men, both 28 years old and originally from Sweden, are believed to have ridden the trolley down Coogee Bay Road, Randwick, in the Australian capital at around 12.20am on Tuesday.

Sydney police said the accident occurred after the men found the abandoned trolley, deciding to ride it - with one on the back and the other inside it - until they crossed to the wrong side of the road and struck the vehicle.

"The estimate is that the men were travelling about 80km/h in the trolley, so they had certainly gathered some speed," Chief Inspector Chris Stiles told The Sydney Morning Herald.

Both men were treated at the scene, first by the 45-year-old motorist (who was not hurt in the crash) and a passing cyclist, and then by police and paramedics. One of the men died on the scene, while the second was taken to the Prince of Wales hospital where he remains.

"It sounds like they might have had a bit of fun together, resulting in this terrible incident," the chief inspector added.

Local reports indicate the first man had been studying and working in Australia, until he was joined by his friend roughly a week ago. Officers are continuing to investigate the crash.