functional urban art?

I decided to take a road less travelled today, on my drive home from work. Sweeping down Dee Road (I think that's the name) I found myself on an unadopted track looping underneath a bridge spanning the river.

I was aware of a few suspecting stares from walkers-by whilst blipping this pic of some markings spray-painted by officials of some kind (workmen I presume), but managed to avoid feeling embarrassed. Less than a foot away, in a lighter tone of blue, was the tag of a proper graffiti-ist and a not-so-moral message to children on the merits of smoking weed.

Tomorrow should be a good day. newcamera arrives...