Pretty sure those are old signs when they had speed camera vans.
There's wreckless speeding and then there's setting up a speed camera van at the bottom of a hill and catching everyone going 10km/h over the speed limit. When it's more of a cash grab than anything to do with safety. Which is the major reason people hated them.
I think the thinking on announcing speed traps is that it will help slow people down. Is that effective? Who knows.
And I personally find aggressive drivers to be more of a problem than just out right speeding.
RCMP Traffic Services:
http://traffic.bc.rcmp-grc.gc.ca/Vie...1&contentId=-1