Why is it 'get in a car', but 'get on' a train?     -Laura

First, there is often little rhyme or reason for why phrasal verbs work the way they do, and that of course is what makes them difficult for non-native English speakers.

When it comes to 'in' versus 'on'...my interpretation is when you are in a car you are in a car, which is to say inside of a car.

Of course, when you are 'on' a train, you are most likely also inside of an enclosed space, but the difference is that the train is like this one long board, kind of like a surfboard, that everyone gets 'on'to as it rolls along.

Planes are also like surfboards that just go along as people get on and off too.

But cars are like your own little personal space that you get 'in'to, as opposed to the one long public board that you get 'on'to.

Again, this is just my reaction to the fact that this is the way it's said in English. It will probably not be a great rule of thumb to use when predicting what prepositions to use in English in general. But it's the way 'in' and 'on' look when comparing the small enclosed space of a car versus the long board of a train or plane.