We shall talk about the average city bus.
Average bus -> ~13000kg. I checked multiple sources, not only the one given. Passengers' weight is neglected considering the strong rounding on the bus weight either way.
Let's consider multiple probable cases.
- Bus crashes into something stationary in front of it. Bus probably tried to stop beforehand.
- Bus crashes into something moving. E.g. A car that suddenly came from left/right.
- A light car crashes into the bus from left/right. In the front part of the bus.
- A light car crashes into the stationary bus from behind.
From multiple searches I might put the average car weight to ~2000kg
I believe the bus speed doesn't really matter for the sake of the question, since it doesn't change the safest spot. But I might be wrong, so let's consider speeds of 60km/h in town and 110km/h on a high road. Or whatever speed you find to be relevant.
Nobody wears seatbelts.
- The people in the bus are average weight. Let's say 70kg (~55kg for women, ~82kg for men)
- By "safest" I consider the situation where a human sitting in specific place hits his head on the seat in front of him mugh/slightly lighter than the man sitting in the most dangerous place.
Also would be nice to have a statictics about bus crashes, which crashes happen more often etc. I shall add it later on.
I understand that the question might be a bit out of the scope of the physics SE. Let's just make sure that those of the human species who care about little things, feel safer on the public transport.