Sure but again, just like packing people onto a bridge like sardines, it's an unusual circumstance. While vehicles driving all day over a bridge is not unusual. And even vehicles getting stuck on a bridge due to some traffic issue is not unusual either.

One has to consider what is daily use, not just the exceptional cases.

> One has to consider what is daily use, not just the exceptional cases.

generally it's the exceptional case that it's designed around though

I'm not sure I understand that comment. "Well, yeah, the bridge collapsed but it was an exceptional case. It worked fine for typical daily use."

Here is how I understand the comment:

We have a car bridge designed to withstand exceptional load, and a pedestrian bridge designed to withstand exceptional load. The commenter assumes that on average, the car bridge's load is much closer to it's maximum load than the pedestrian bridge's load, and in consequence, the average wear on the car bridge should be higher than on the pedestrian bridge. As such, the pedestrian bridge should have a much longer lifetime, and the commenter assumes that this is the reason old Roman bridges are still standing.

Their question is: is this assumption correct?

It probably is not correct, because the pedestrian bridge max load is probably something like "what if an idiot drove a car down it" whereas the car bridge max load is "what if it was full of very heavy trucks and one burst into flame".

You also have to take failure modes into account, and how degraded the bridge can get before it's "unsafe".

Sounds good to me, ship it.