Use of speed signs

Hi! Ever since RS came out, all routes have had speed signs, and signs showing approaching speed changes. Is the use of these signs a UK/Europe situation, or as my limited observation of real North American railroads indicates, they do not use speed signs. For the simulator, for speeds to show only on the HUD, I am tempted to place the appropreate sign, then bury it so that it does not show beside the track. Could someone please post as to wheather speed signs are actually used on NA railroads? Cheers; Chuck F.