Hey, I was curious as to why my school bus is shaped so uniquely.
Being 16, and without a car I need to take one 5 days a week…
Anyway, you know what I mean, it looks like someone messed up and didn’t put another set of wheels in the rear end! I see the 2 wheels in the front end, for stering and another set of wheels a little off center. Why is this?
Why aren’t the wheels all the way back? Is there not a chance of tipping if the load gets to great on the rear?
Everything about your school bus is set out in Standard CAN/CSA D250-00, published by the Canadian Standards Association. The standard is extraordinarily stringent - school buses are probably the safest vehicles of any kind in North America. A kid is probaby twenty times likelier to be killed getting to the bus than to be killed in an accident riding the bus.
The weight of the part of the school bus beyond the rear wheels simply isn’t significant. The fattest students in Canada could be carrying barbells back there and they still wouldn’t tip the weight of the engine and the fuel tank, both of which are well forward. The rear wheels have to carry most of the weight of the body, so they’re relatively centred.
Before anyone asks the other usual question, “Why don’t school buses have seat belts?”, it’s because they don’t need them. It isn’t worth the effort for the minimal safety impact it would have. In fact, it’s believed kids would probably suffer more injuries as a result of being whacked with the buckles and strangled with the belts by their peers.
I suspect you’re right. I further suspect that if the wheel were further apart the bus would need a stronger, hence heavier and more expensive, frame to prevent excessive flexing.
As far as the seatbelt thing goes, it depends on how you look at it. Yes, the school bus safety record is excellent. But if you take a look at the relatively few serious injuries and deaths on school busses, and then ask what could have helped prevent them, then compartmentalization shows its weaknesses.
In a frontal impact, compartmentalization works fairly well, but the distance the children travel before they smack into the padded seat in front of them is problematic. Rear facing seats would be a significant improvement, as would three-point seatbelts. Would kids be content to sit facing the rear, or would they wear the belts, or could belts be installed to fit the wide range of child sizes? Your guess is as good as mine.
But unfortunately, busses do roll over. When they tip over on their sides, compartmentalization often fails. Kids become spam in a can, as they fly through the coach and eventually slam into something, or fly out the windows. That’s where most of the deaths, dismemberments and severe head injuries arise. The benefits of compartmentalizetion are lost when the kids fly out of their compartments, and in as much as three point restraints could keep them in their compartments, then three point restraints could save lives that otherwise would be lost, if a particular design could be made that would not focus too much force from the belts on small areas of the children.
A good place to start digging about for information on this sort of thing is the US National Safety Transportation Board’s report on Bus Crashworthiness Issues. I’d suggest reading through Appendix F prior to delving into the report.
To expand on that. The seats on a school bus will tilt foward during an accident. The is, if something hits them from behind with significant force they will give (as opposed to staying rigid) to absorb the force.
Keep in mind the old law of unintended consequences.
Put in belts, and buses become significantly more expensive. School districts may then buy fewer of them and have many students walk to school instead.
