I’ve just started to take the bus to work everyday, and I’ve noticed that the bus driver pushes a button when he reaches a bus stop that lowers the front of the bus. I don’t think it lowers the back of the bus. This makes is easier for someone to step onto the bus, but then as soon as the door closes I see the bus raise up again to its “driving height”. Next bus stop, he lowers it again, althought I’ve noticed that sometimes he forgets.
So what’s the deal? Why would the bus have to be higher when moving than when loading passengers? Can someone please enlighten me?
That’s a “kneeling bus.” It lets air out of the front suspension which lowers the front end of the bus down close to the curb to make it easier for seniors and the disabled to get on. You can’t be driving around with the suspension like that and bottoming out the front end of your bus though, so the front end is pumped back up when the person gets on.
Folks just explained it, the higher the bus body rides the more room you have for suspension travel. This allows the bus to ride over rougher terrain without throwing everyone in the bus into the ceiling.
Rough terrain? We’re talking about city streets here, not a motocross course. I’ll take it on faith that the benefit of this added clearance is worth the obvious cost of having a hydrolic suspension.
BTW, not all buses can do this, and the ones that don’t do it don’t bounce people all around.
Have you been out on city streets? They’re full of potholes. If the suspension weren’t giving enough, I guarantee everyone on those busses would have headaches after the ride. The ones that don’t kneel already ride high for the above mentioned reasons.
Most buses have plenty of compressed air to spare, (The brakes and doors are already air-powered) so the kneeling is done pneumatically. The “Pssshhhw!!” noise when the bus kneels is another good indicator.
An alternate to kneeling buses is what I can only describe as a low-deck bus. Not sure who builds them, but I’ve been on one or two of them where the floor is only about six inches off street level, instead of two feet. Seating behind the rear door is up a couple steps as the drive train has to be under the floor.
The main drawback is huge wheel wells up front taking up space that would otherwise be seats, and there must be some suspension considerations as well. As in how do they avoid dragging the body along when going through potholes? I suppose these buses are fine for transit agencies that don’t want to put out the money to buy kneeling buses or wheelchair-lift buses, or don’t have the maintenance ability to keep the things working. (The kneeling / lift functions are among the top five or so reasons that will keep a bus from running.)
They seem to work well in flat land, but in places like San Francisco where you need to be concerned with a vehicle’s approach and departure angles, they just wouldn’t be able to handle the hills. Trust me - it’s quite a jolt when the bus’ frame bottoms out against the pavement coming off a hill. :eek: