So....

You must not have been very attentive, the movie actually states that a couple of bikes on the track will NOT cause the trail to derail. It was a faulty memory of Peter's as part of his repression of what actually happened.

Towards the end of the movie they actually showed very clearly what caused the derailment, did you miss that??

..*.. TxMike ..*..
Sometimes I think we're alone in the universe, and sometimes not.

*SPOILERS*

The part with the bikes derailing the train is a figment of Peter's imagination, as we learn at the end that the derailment was actually caused by the girl pulling the lever for the switch.

As for the car, it was an older model, wasn't it? So it might make sense for it not to have that safety feature. Are you referring to an escape latch that opens into the car itself (my car has this) or something you pull that opens the trunk from the inside?

Baran_erik, did you even watch the whole movie?! They blatantly said that's not why the train detailed. It's because the girl was getting raped and grabbed the switch that changes the rails, which made the train go into a turnout at a high rate of speed...which then made the train derail. Duh.