To punish them for building a cool bridge or?

Well, it's a good way to check their confidence level of their work

It's only a punishment if the bridge falls down. But if someone is making truck drivers drive heavy trucks out onto a bridge to "test" if it will stand up under the load it only seems fair to me that the engineers who designed and built it take the risk alongside them.

I'm positive those trucks are self driven. There is no need for draconian measures you hoped for. Spaceship engineers aren't forced to go into space.

If crossing the bridge you built is as dangerous as going into space, you've clearly done something wrong.

If you see it as a punishment to be the first to cross the bridge that you designed, then you should probably be increasing the factor of safety in your calculations and the number of site checks you conduct.

Key stone?