In the first photo.
That is new, it has only been there for a couple years. Prior to that you could drive right down to the Arch, indeed people drove right across the arch. I never had it in me to try that in my jeep, but I saw a quad do it once.
The second photo you may have found, but if not trust me it is there, a memorial to a jeeper who went over the cliff. He was the uncle of a friend of mine. As it turned out he had neglected to put on his parking brake and the vehicle started to roll off the cliff. In an effort to save the valuable jeep he jumped back in, sadly failing to stop the jeep he and the jeep went over and it killed him (obviously).
I am not sure now, but you can see a road at the bottom of the canyon, you used to be able to drive right up to the base of the arch. LOTS of sand, but a very nice drive/ride as well. Someone told me that road was closed as well, so I have not been back to find out for sure since. The blockade of the top (first photo) was such a disappointment that we have not been back often at all. Just so you know beyond where the sign now is the road went over several large steps to get down to the arch, and it was a lot of fun to enjoy getting down there. Also when you are coming in from Moab there are several large steps that have been ground down my heavy equipment, presumably in an effort to make it more accessible to people who would then have to walk to the arch.