There are some partially tarmacked military access roads on the moor just above Okehampton. They have deliberately been allowed to decline into a rather rough and potholed state and most local visitors only use them to get to the top of the hill above Cullivers Steps where nice views can be had and there is space to park off the road. You could back when this photo was taken, still drive around the narrow little ring road which will take you into the heart of the moor but a 4x4 or maybe a Citroen which can raise its suspension is advised as there are deep holes in the road and a rather steep and perilous ford half-way around.
The road to the right past the gate alongside the river that parallels Army camp only goes as far as the saddle on the side of West Mill Tor and very badly eroded half way up the hill (2019 they have repaired it); and has little parking space up there. You can however stop at the bottom of the hill and walk on the stone paths from there. Private vehicles are not permitted to drive or park on the moor off the roads and there are signs prohibiting vehicular access beyond certain points. The Ranger will not take kindly to people who think they can take their private 4x4's up the rough stone tracks which are for military and farmers vehicles only.