More than 400 cyclists were fined or cautioned for failing to wear a helmet during South Australia police's Operation Safe Cycling, while only three drivers were cautioned for failing to keep a safe distance from cyclists.

Changes to cycling rules introduced in late October require drivers to leave a minimum one-metre gap when overtaking cyclists when the speed limit is 60 kilometres per hour or lower, or 1.5m when the limit is above 60kph.

Police had been letting drivers off with a warning until late January, when they said the "three-month education phase" was over.

But over the three-week operation, only three drivers had to be cautioned.

The fine for failing to comply with the laws is $287 plus a $60 victims-of-crime levy.

The new laws also allow for cyclists to ride on footpaths.

Police said there were more than 800 incidents in total during the operation, which coincided with the Tour Down Under.

Hundreds of other cyclists were fined for ignoring traffic signs or signals and for riding without lights at night.

Drivers were also pinged during the period for parking or driving in a bike lane.

Police said more than 500 cyclists were injured in crashes in 2015, and four were killed.

Meanwhile, an 88-year-old man from West Lakes in Adelaide's western suburbs has died after coming off his bicycle at Henley Beach on the weekend.

The man was found lying on Cudmore Terrace early on Saturday and died in hospital yesterday.