This sign on Whitehall Terrace is attempting to communicate to drivers that they can take an immediate right onto the ramps to the Grand Central Parkway, but are not allowed to cross the striped-out median area to turn right onto the Clearview Expressway ramp.
What's especially weird about this situation is that vehicles heading west on Whitehall Terrace, like the car above, encounter no indications, other than this cryptic sign, that they're approaching the Grand Central Parkway and are about to be forced onto it. Whitehall Terrace is just a little local street where drivers unfamiliar with the area might end up while looking for something nearby. Hoping to stay in the neighborhood, they'd turn right at the stop sign — the only direction you're allowed to go — and suddenly find themselves having to decide within about 70 feet whether to take the eastbound or westbound ramp to a parkway they never intended to be on in the first place.
You almost definitely have more knowledge of the present condition of the streets of NYC than DOT. Maybe contact DOT with an email and somehow tag them on these posts? Or just send them an email with a link to the post? I know it would probably make their day to see someone, who isn’t a complaining resident, make an objective critique of a bad intersection.