FOUR in every five crashes between cars and bicycles are caused by the driver of the car, police statistics show.

The study by Adelaide University's Centre for Automotive Safety Research could end the long-running debate between drivers and cyclists about who is to blame for accidents.

Researcher Tori Lindsay studied the cause of bicycle accidents from police statistics after a large increase from 12 per cent of all crashes resulting in hospital admission in 2001 to 17.4 per cent in 2010.

The study focused on the most serious injuries - 61 patients at the Royal Adelaide Hospital who were the victims of collisions with cars from 2008-2010.

"More than 85 per cent of the cyclists in the study were identified as travelling straight on a single carriageway with the intention of continuing straight at the time of the crash," Ms Lindsay said.

"Drivers of vehicles, however, were more likely to be turning, with more than 64 per cent of all drivers undertaking a turn manoeuvre into or out of another roadway at the time of the crash."

Bicycle SA chief executive Christian Haag said the results showed a need for greater education and compliance, mainly for drivers.

"It is also important for cyclists to educate themselves and not just jump on a bike when they turn 45 because their doctor has told them to do some exercise," he said.

Cyclist Jurgen Klus said motorist behaviour improved during the Tour Down Under but quickly returned to normal afterwards.

"You don't keep statistics when you are riding but you see plenty of near-misses in which the driver doesn't even know they have almost caused an accident."

The most serious injuries incurred by cyclists were fractures, followed by those who sustained internal organ injuries. Close to a third of cyclists experienced a loss of consciousness following the crash.

By far the most crashes, four in every 10 of the crashes in the study, involved an oncoming vehicle turning right across the path of a cyclist who was continuing straight.

In six out of 10 crashes, the vehicle driver was crossing two or more traffic lanes while turning right.

In two in every 10 crashes, cyclists ran into cars that were turning from the stem of a T-junction.

Collisions between a vehicle and a cyclist travelling in the same direction were the third most-common movements leading to crashes in the study, totalling one in every 10 crashes.

T-intersections were the most dangerous locations for crashes, followed by straight roads, and signalled intersections.

Drivers were at fault in 79 per cent of crashes and cyclists 21 per cent.