I had overlooked this rusted iron post on Frankfort Street and Park Row. These posts with finned masts…thicker versions of the finned streetlamps that originally lit the FDR Drive, Gowanus Expressway and other roads around town that were built in the 1940s and 1950s… originally held white signs that were lit by incandescent spotlights positioned on the mast. I’d say there are about a dozen of these left in NYC, including two more on nearby East River Drive exit and entrance ramps. Jeff Saltzman has a photo of the signs in their original livery.
To get to the FDR Drive from here, you would continue on Frankfort and turn left on Pearl, where there’s an onramp to the East River Drive (it becomes the Franklin D Roosevelt Drive further north, at Montgomery Street). There, a stanchion similar to this one directs traffic to the ramp.
The lane to the left is closed to unofficial traffic. It takes Park Row past the NYPD headquarters and the Municipal Building; the city closed it off to regular traffic decades ago.
Frankfort Street was named in the 17th Century by controversial New York colonial Governor Jacob Leisler, who was born in Frankfort, Germany. He was convicted of treason by British Parliament and hanged.