train and air travel in Europe

Locks are good for casual snoops trying to quickly get into bags, but if they just take the bag, or have it out of sight in an airport, it only indicates if the bag was tampered with. I have never had a problem with leaving a bag at the end of a car on a train. Most of the time though my bag is small enough to fit above me at the seat. In the event that I do put my bag on the luggage rack, I try to do so that it is in my line of sight. If the train is crowded, at a stop, I may also get up and walk down by the bags to keep a closer eye on it, the most likely scenario is that someone would grab a bag as they get off at a stop and be gone. While the train is moving it is much less likely someone will try to grab a bag.