The article implies that the driver didn't understand the sign. Unclear whether the writer thought that was the actual reason. An alternative reason would be

The article implies that the driver didn't understand the sign. Unclear whether the writer thought that was the actual reason. An alternative reason would be that the driver consciously disregarded the safety notice, perhaps thinking it overly conservative, or thinking that they could get through with only stress to the bridge that's not traceable to them.