The link that I showed you above will help you. However I'll post here too. Trains and buses, as two examples, have a large space in which you can walk up and down. Therefore we say we are 'on' the train, or on the bus. Cars and smaller methods of transport (as the link suggests, hot air balloons, helicopters, small boats) do not have the walking space and therefore you are 'in' it.

Ride on a bus, ride in a bus, ride a bus, take a bus - it all means "to enter into a bus and to be transported somewhere".

On How do you get to school? I come on a bus/I come by bus How did you get to school? I went on a bus/I took the bus There are so many variations How are you going to get there? I'm going to take a bus(have not decided which one yet) I'm going to take the bus(the one that I know goes there) Unfortunately there are so many ways to say it and there are also regional variations which make it even more complicated. My mother would also say 'get in' or 'get on' when she was being impatient outside the bus or train in England.

https://www.quora.com/Why-do-we-say-on-the-bus-or-on-the-train-but-in-the-car This link has good information as to why those distinctions are made.