Why is there such a huge discrepancy between yellow school buses and municipal public transportation buses? I don’t mean the disparity between the side exit preferred for public transportation and the rear emergency exit for school buses. Nor I am concerned with room for standees on public vs. seating only for schools. Not even the small sliding windows for yellow buses vs. A/C for public transportation. All of that makes sense.
My big issue is the location of the rear axle. Both bus types have the front axle located very close to the front of the bus. However, for city buses, the rear axle is located in the rear, while school buses have the rear axle typically located two thirds of the way back from the front for a long bus. And while were at it, city buses typically have a flat front, while school buses have the typical “Mac Truck” nose sticking out.
Now I’m no bus expert, but this seems like the primary function of either is to transport people from here to there, in tough to maneuver areas, safely and reasonably comfortably. But the current setup requires two distinctly different chassis. Why wouldn’t a bus manufacturer just figure out a common design that will work with both, and customize the finished bus to the public trans or school use?
The wheels in a city bus are in the back because city buses have the engine in the back. School buses usually have the engine in front with a driveshaft to the rear wheels. The rear axle is moved forward to carry more of the load, and I would guess that the shorter wheelbase makes it easier for coaches and schoolteachers to turn a bus on city streets.
There might also be a limitation that the driver must have a commercial drivers license for any bus with a longer wheelbase.
Most “city” buses are now rear-engine designs, so the whole engine and transmission package sits atop the axle, much like a typical front wheel drive car. The engine and trans need to be near the outside for serviceability. A mid-engine design would be difficult to work on, so it’s been pushed out to the tail. Having the engine under the seats also makes for a necessarily higher floor (more steps to climb) and more noise inside the bus, especially if some twit gets curious about what’s under the hatches in the floor and opens one.
The older front-engine school buses are also rear-wheel drive, and have a long driveshaft. Running the shaft all the way to the back end would involve added complexity in the form of support bearings and added segments and U-joints - a long shaft would tend to flop around - so they put the driven wheels about 2/3 back on a shorter shaft.
Nobody wants to spend much money on school buses, so they’ve used that classic front engine and driveshaft design for decades because it’s simple and fairly cheap. The newer rear engine and transaxle design is relatively new, a bit more complicated to engineer and a bit harder to work on, all of which makes it more expensive.
FWIW, most of the school buses here have switched to rear-engine designs in the name of safety. The engine out in front creates a huge blind spot for the driver. Our very own **Mr Bus Guy ** can expand on this and might even have stats on how many fewer kids are being hit by the bus when they cross in front of it and the driver can’t see them.
gotpasswords nailed most of it. Kids don’t weigh much, so the rear axle can be way forward. Due to weight-per-axle rules, builders get both axle to share the weight of the engine. In a rear engine rig, the front wheels are behind the passenger door.
Both kinds of buses also have pop-out emergency windows. Some buses also have emergency roof hatches for accidents where the bus turns over.
Could different road types account for differences? I think that city buses can expect to always run on (relatively) smooth, hard paved roads, while school buses may have to deal with a wider variety of roads, and road conditions. I grew up on gravel, and regularly spent 30 to 45 minutes (one way) on a bus route that was 50% or more gravel - and spring thaws aren’t all that nice to gravel. I never had to worry about the bus getting there (except for a week, some years, when a bunch of us had to get down to the hard surfaced roads because the gravel was too soft for anything more than a pickup), but I wouldn’t think a city-style commuter bus would do well at all under those conditions.
School buses are also built on a five-ton truck chassis, and city buses are a completely different animal. I expect an unbuilt-upon five-ton truck chassis is a lot cheaper than a city bus, and adding the frame and seats probably doesn’t cost much either.