Did you know that when we use the preposition в with means of transport, it means you are inside the car, bus, ship, plane, etc., and when we use на, it means we use this mean of transport to go somewhere. In both situations, the Prepositional case is used.
- Я читала газету в автобусе. I was readind a newspaper in the bus.
- Я ехала на автобусе. I was going by bus.