"I still think the steel looks lightweight."

Nope. It's fine but there is a "procedural" flaw, not a design flaw. This flaw is no where near the bridge. I have said since I was an engineering student over 30 years ago that weigh scale stations should have a "sizer", as I called it back then, thru which vehicles must pass. If they cannot pass thru, they have to park until they have the proper paperwork. This paperwork is REQUIRED to be obtained in EVERY jurisdiction in NA, Europe and beyond prior to entering a jurisdiction with any "overload". But, every now and then, some yahoo without a clue overloads or oversizes for whatever reason and serious shit happens.

My idea would add less than $6k to each set of weigh stations. Simplicity is beauty and safety is paramount to an engineer. One penny extra is ugly to a pencil pushing accountant or politician. Sad. Also, the modern weigh-in-motion stations would almost preclude provision of this simple device because some lawyer would file a law suit eventually.