The Bridge, which was made by Mazda, is different for each person depending on how wholesome and wonderful they were. Lead a good life and the bridge is wide. Lead a bad one and it's narrow, and possibly wobbly and slicked with irregularly spattered dog s**t. And here's a part we thought was wonderful: if you've lead a great life, you get a really hot chick (or dude if you're a woman) to accompany you. If you're a nasty person, your guide is dog-ugly and probably shouts at you as you try and get across.
So basically if you're a clumsy idiot, or have clubfoot, or are wheelchair bound and you've got a wobbly rear wheel, you can go tumbling off even a fairly wide bridge. Zoroastrian hell is probably filled with the souls of generous, caring people who just happened to have an inner-ear problem.
The other end of the scale isn't any better; if you've lead a bad life, the bridge is very, very thin (how thin, we're not sure, but let's imagine a sliding scale between the width of a small child's hips if you spent your youth taunting blind people, to the width of a standard dress loafer if you robbed a bank). Either way, if you're a capable balancer, or even have a modicum of control over your flapping extremities, you could probably get across that bridge with no problems.
Basically if you wind up in Zoroastrian heaven, avoid the tightrope walkers.