Speed Limits can and should be added to the map using WME where applicable.
The instructions and technical details for how to enter speed limits in the WME is explained in the Speed Limits section of the Creating and editing road segments article.
Local country pages
Each local community may create a wiki page specific to their local usage and guidelines if they choose to.
The communities which have already created local pages are listed below, please visit the page for your community to see the local guidance for where and when to (and not to) add Speed Limits.