I'm on the road for the next couple of weeks so don't have access to the library but for a down under perspectrive, I think the old Manual of Land Warfare (MLW) The Rifle Platoon or The Rifle Company had tables for infantry movement across a variety of terrain types.

Uncontested movement over relatively flat or undulating firm ground with no signification foliage obstacles would probably be midway in that 15-30 mile range.