I have some familiarity with public transit...
The Nova artics jackknife like it's their job with any type of snow or ice on the ground. I imagine most manufacturers' artic buses do this if similarly designed. They have to be pulled from service an replace with another bus when it starts to snow, unless the route they're on is dead flat and the it's piloted by a decent driver. They'll even jackknife on a wet concrete floor when going slow pulling into a parking lane. The driver will be applying the brakes and the center axle will lock but the idling engine has enough power to keep the rear wheels pushing bus. The only solution is to brake harder to stop the rear wheels, but this is counter-intuitive for most drivers. Releasing the brakes completely might also work but it might not, and you're usually closing in on a wall, pole, or another bus anyway, so you don't want to fully release the brakes...
In the US, you can't really find high-floor buses anymore. This is for customer convenience (no steps except in the very back) and for customers with disabilities. This means the engine has to be pushed to the rear, powering the rear axle. If the middle axle was powered, jackknifing wouldn't be an issue. Manufacturers are saying they're working on bringing a electrically powered middle axle to market in a few years. It's not clear if this will be the sole driving axle or just as part of a computer controlled traction control system meant to preventing jackknifing.
Older buses used a "pancake" engine (horizontally opposed cylinders I believe, or maybe just a straight 6 on it's side) in front of the center axle. I'm sure they were harder to work on but they probably didn't need as much attention since there was hardly any emissions stuff on them. And things were a little more lax back then... (if a Detroit 6V-71 wasn't leaking, it wasn't running!)
Also, most manufacturers now use super-single tire in the center axle instead of traditional duals. Those wide tires ride on the snow instead of slicing through it. And with low-floor buses there's not enough room for chains, and those cause massive damage when they break.
There's no way to lock the artic joint to keep it from jackknifing, but once it's jackknifed the bus locks out the accelerator so can't be moved until a mechanic overrides it. This is to protect the (very expensive) artic joint. And it's also good for snarling traffic since the jackknife usually occurs in the middle of an intersection.
They're pretty slow on acceleration. And engine power is limited in turns to protect the articulation joint. Engine power might also be limited in first gear as well.
We have a bunch of buses, both artics and 40-footers (New Flyers), equipped with Allison's parallel hybrid drive system and a Cummins ISB. They work well. Maintenance is virtually the same as it is on the non-hybrid (Cummins ISL equipped) buses. The hybrids are quiet and smooth.
Scott
