For the curious, here are shots of the Hyde Park tract that will be gated and locked to keep pedestrians and cyclists from using 50th St. (clipped from Google's Street View). First, the overhead shot of the 50th St. entrance to the tract (the tract is on the left):
Next, the street-level view of the 50th St. entrance (sorry, just a jpeg -- you can get to the Google street view using the link immediately above):
50th Street, of course, is a public right-of-way. As you can see, there is already connectivity for cars as well as for walkers and bikers. The neighborhood plan, presumably, will require the developer to replace the chain-link fence with a lockable gate capable of blocking foot and bike traffic.