Prepositions with Transport

• Use "on" for public transport that you can walk on: bus, train, ferry, plane, coach.
• Use "in" for forms of transport which you sit in, but can't really walk in: on a plane/on a train/on a bus; in a car/in a taxi/in a small boat. 

However, This rule sometimes works, but other times it can be misleading you and others into believing that there is some kind of a grammatical rule about prepositions and modes of transport. Well, there are no rules. There is nothing wrong with "in the bus." It is used less frequently than "on the bus."

As regards means of travel, "by" is used when the reference is to a general means (e.g. We shall go by car/bus/train/by helicopter, etc.), but when a specific vehicle is referred to, then appropriate preposition for that vehicle must be used—usually either "in" or "on" (in my car, in his own aeroplane, in a taxi, on my bicycle, on the ‘Mauretania’).

If the vehicle or means of transport is identified merely by the time at which it starts or arrives, either "by" or "on" may be used.

• I shall go by (or on) the 10:30 train.