Brazen teenagers have filmed themselves breaking into guards’ compartments and dangerously playing chicken with moving trains on the Sydney Train network.

Last month, a group of trespassers narrowly escaped death after jumping onto the tracks at Petersham in the city’s Inner West.

The group were attempting to break into the rear crew cabin on a train heading to the City-Circle, when an express service from Richmond headed straight towards them. They were forced to run, only just missing getting hit by the oncoming train.

They are seen playing 'chicken' with oncoming trains and tunnels, moving inside just in time to escape getting hit. (9NEWS)

The driver stopped, thinking he had collided with one of the teens, and the incident saw two services cancelled and delayed 65 others for up to 40 minutes.

"The driver... he thought he had killed someone in that incident." Sydney Trains CEO Howard Collins said.

9NEWS has also obtained videos uploaded to social media platform Snapchat, where young boys hang out the doors of carriages, only ducking inside just in time as trains and tunnels approach.

In one video the group break into the guard's compartment, push buttons and play with the windscreen wipers. They also film themselves vandalising doors and walls with a black marker.

In one one, the group break into a guard's compartment and play with the controls. (9NEWS)

Fines for trespassing can reach up to $5,500 on the Sydney Trains network. (9NEWS)All of their faces are clearly shown in the unedited video.

"Not only are they idiotic, but they have gone and filmed it and left a digital footprint for them to be prosecuted," NSW Transport Minister Andrew Constance said.

A train's movements cannot be altered from the rear crew cabin.

There are more than 11,000 cameras across the Sydney Trains network and fines for trespassing can reach $5,500.