I’ve been in Paris for the past few weeks, and one of the road-related things that I’ve noticed is that road signs are three dimensional, in that the side of the sign is wider than the metal used to make the sign. The edges have been drawn out somehow, as you can see in the no parking sign below.
Is there an engineering reason behind this difference? Or is it mostly a question of tradition and aesthetics?
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi65.tinypic.com%2F2eqexb9.jpg&hash=f493951e67992e68224ef100c181ec7b7212cddb) (https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi63.tinypic.com%2Fzx2lht.jpg&hash=204877099c963ab9d6ddcb9ba01909877c066b42)
I suspect mechanical stability of thin metal. So it comes down to cost of pressing the shape vs cost of thicker metal
That would be my guess as well. Especially on a round sign like this, that edging should provide a bit more durability should the sign be struck on the edge.
Nevada DOT tends to use extra bracing/stiffeners on signs to attempt to achieve greater durability. (example round post (https://goo.gl/maps/cJt6WexDZCFS1HXw9), example square post (https://goo.gl/maps/XzYCuqYJCNpMoHSk9))