As a non geocaching muggle, I thought very little about guardrails. Perhap I would notice when they were between me and a fairly percipitous drop, or when they kept another vehicle at bay. Now that I've been involved in the sport, I SEE GUARDRAILS EVERYWHERE!!!! Miles of them! Along highways! At the approaches to bridges! Down the street from my house! The possibilities are endless! I now see what I never did before. Guardrail caches are my calling, my siren song.
Granted, the view is mostly industrial, but there is a certain beauty to the cranes that unload the ships at this working port, and with this comes traffic. Rush hour in the morning and afternoon means this place is high in muggle activity, so keep this in mind when going after this cache. An ideal night cache.