Origin/reason for the expression “on the bus” instead of “in the bus”
I'm an EFL (English as a foreign language) teacher and I haven't been able to come up with a good principle for which preposition to use after get when referring to transportation.
- Get in:
- a car/taxi/van/truck, etc.
- Get on:
- a bus/plane/bike/truck, etc.
How can one choose whether to use in or on? Note that in some cases, such as the example with truck, either preposition is possible but the choice affects the meaning.
I've been telling my students that there is no rule, so they just have to memorize which preposition to use, but I'm really hoping I'm wrong.