If the radar cannot distinguish between a bridge with five meters of clearance and a "bridge"(trailer) with a single meter of clearance, then the radar simply l

If the radar cannot distinguish between a bridge with five meters of clearance and a "bridge"(trailer) with a single meter of clearance, then the radar simply lacks the angular resolution to be effective. It's the same exact issue as it being unable to distinguish objects on the side of the road and objects in the middle of the road. It's insufficient angular resolution for the application, no matter which way you slice it.