text: The DPA impose a speed restriction "to minimise erosion, preserve tranquillity and ensure the safety of walkers and livestock," according to the bods at the DPA visitor centre. Somewhere on the notice board at Moorgate there used to be a "Take Moor Care" poster which mentioned it  - it's some years since I stopped to look at the board when driving up to Rowtor parking area but I presume it's still there. I vaguely recall that there is a sign on the gatepost at the cattle grid explaining the permissive nature of vehicular access which I think also mentions speed being restricted to 10mph. Presumably if there was no other restriction then by default, under the DPA rules setting a blanket limit on any moor road likely to be accessed by grazing animals, it would be 40mph as the military roads in whole or in part always have sheep or the odd pony on them when I go up there...?
  I'll concede your point on the vehicle access, though, as farmers and park rangers are also allowed access and have changed the affected roads accordingly. Original tagging was as a result of over-analysing the Wiki page and reading it as needing a "no" because ordinary folk couldn't ordinarily drive along it.