On my road running Altra Torins I ran 3 miles in intervals on the following surfaces:
+asphalt (has some spring, and impact absorption)
-concrete (almost zero spring or impact absorption, hell on joints, hell on eyes in bright sun)
-Ice under snow over asphalt (courtesy of JustDeb who says, “Don’t run on it!”)
+sandy clay (nice absorption, poor drainage, muddy)
+ground red granite gravel (best for all around drainage, absorption, nice on eyes in full sun)
+road base rock (good variety for lower extremity muscles, rougher on shoes)
+dried clay mud (variable, better absorption, sometimes hard / trippy, crackly / dusty)
+wild grass (variable, take a quick break or two to police for ticks – catch ’em early and tweak ’em off)
Can you guess which surface I do not recommend for running but which nearly every short-sighted developer and city planner in my area prefers as a trail building substance between subdivisions and open spaces, and in some cases, through open spaces? I’m sure you can.
Concrete has many positive uses. Running trails are not one of them.
Disclosure: I find it a pain to take photos while running so I cannibalized past photos of multiple surfaces…