alt Hacker NewsUm, ackshually, real civil/structural engineers—at least, those in the global north—design bridges, roads, and buildings with huge tolerances (multiple times the expected loads) because unexpected shit happens and you don't want to suffer catastrophic failure when conditions are just outside of your typical use case and have a Tacoma Narrows Bridge type situation on your hands.
We might be arguing semantics, but safety margins aren't considered 'overbuilding' but part of the bare minimum requirements for a bridge to stand. They aren't there "just in case" they are there because it is known for a fact that bridges in the real world will experience degradation and overloading.
If you build a bridge that is rated to carry 100k lbs of weight, and you build it to hold 100k lbs, you didn't build it to barely meet spec -- you under built it -- because overloading is a known condition that does happen to bridges.