Young Australians are getting their kicks in a dangerous way - climbing onto the backs of moving trains to take selfies.
The 'buffer riding' problem has gotten so bad, train bosses have asked engineers to redesign the carriages to make the practice impossible.
CCTV pictures obtained by Channel 7 News show it's an issue all across Sydney.
Youths climb onto the back of the train to take a selfie, then casually jump back across to the platform.
"Don't play on our trains because the consequences could be serious injury or death," says Sydney Trains spokesperson Howard Collins.
Last year more than 2400 people were reported for trespassing into the rail corridor - four were fatally struck by trains.