Originally Posted by
wphamilton
Well "hard" as opposed to "soft" is pretty much a given. Most everything causing an impact or sharp acceleration will have a surface impact. "Flat" possibly refers to sidewalks and roads which are leading locations for falls. Along with residences for which falls are mostly bathroom, may or may not be flat. Or it may be from his helmet researches which do show that impact on flat surfaces are the most likely to result in TBI. I don't know that it's worth arguing about, or the trouble to source.
Most residences have stairs. Stairs have little relevance to cycling. Holding up simple falls as the leading cause of TBI and thus heralding the bicycle helmet as the cure without considering why those falls happened (and further posting about it as if the assumption is fact) is a bit misleading, but not surprising. And then there's the whole severity thing.