What Does This Sign Signify And Where Have You Seen It?

I found this lovely old bridge, in the area, by mistake taking a wrong turn - crossing the Rhine. One end of it is modern steel, probably a repair from WW2 damage. The rest of it is like the picture. Sometimes just have to get off the bike and make the effort to take some pictures !

 

Ah it was a few years back 2016 I went, it was quiet back then not many bikes.
I was on my VFR1200