Haha, I imagine that's either a cross between a load limit and speed limit (4.8T on a low limit sign?) or a really bad unit conversion. It's not enough a round number of kph. Submit it to TDWTF.
I'm assuming that is for diggers and heavy machinery and stuff. Most cars speedos don't even go lower than 10 I think.
http://www.chroniclelive.co.uk/nort...s-bemused-by-9-5m-speed-limit-72703-29101258/ Hmm... seems like it could be a clever psychological technique to make people pay more attention (which would seem to work ). Cheeky. In this case probably just an inappropriately precise conversion of 3mph into kph though