[bombcar]

The problem comes when those type of bridges don't collapse the first time someone overloads them; then people start using it because "eh it works" and eventually it fails.

[pmontra]

Is there some well established way to make some very visible but not structural part of a bridge to collapse after an overload, to scare people and make them report the problem?

[bombcar]

You probably could, but the amount of engineering and cost required would be simpler to just replace the bridge with a stronger one.

Often these "car only" country bridges are just some large wooden beams over a creek; even a simple concrete culvert replacement would be truck-proof.

Some of them do things like this: https://www.alamy.com/stock-photo-small-car-suv-crossing-the...

[yonaguska]

A really simple catch all, that isn't quite accurate for all cases would be to put a sign over the top of such a bridge,that limits the height of vehicles crossing, excluding trucks with the tall trailers. Would not work for loads that aren't tall though.

[mannykannot]

I would have thought a few strain gauges, maybe some logic to filter false positives (if that's a risk) and a light would do a reasonable job.

[bombcar]

Wait until you see the known issues and reports on bridges in the US that did collapse. Nobody monitors this stuff even on important ones.