Sometimes I think it is strictly for insurance reasons that signs are erected.
I believe that this road closure is to prevent over-weight vehicles (mostly farm tractors and wagons) from suing the municipality if they fall through a bridge designed for lighter weights.
But then they post the signs for all vehicles - which regular passenger cars and trucks ignore!
All photos and signs are from the same road and bridge.
The road and bridge are fine - even I use them occasionally!