Route 120A is probably the strangest highway in Connecticut. It's exclusively a New York state route – ConnDOT does not define or maintain any part of it – but spends half its length on King Street in Greenwich. At times it straddles the state line, including an interchange with the Merritt and Hutchison River Parkways that the two states assign different exit numbers.
There's a Connecticut-style route marker (photo) at the end of an exit ramp, and a New York-style marker (photo) once you make a right turn. Both are on Connecticut soil. I haven't seen any other Route 120A markers in Connecticut.
Take exit 30, er, 27, I mean 27S
Connecticut's Merritt Parkway was given exit numbers in 1947 continuing from New York's Hutchinson River Parkway; hence Exit 27 for King Street, the first exit in Connecticut. However, New York later renumbered their exits, resulting in their side of King Street becoming Exit 30.
In 1999, the Empire and Constitution states announced a cooperative plan to rebuild exit 27/30. A public hearing was conducted in February 1999.
The project, the final part of a decades-long rehabilitation of the Hutchinson River Parkway, would extend about 500 feet into Connecticut. King Street would be widened to five lanes and sidewalks; the bridge would be expanded in a manner consistent with its arched stone forms. The cloverleaf interchange would be modified to a six-ramp partial cloverleaf, with four onramps but only two offramps, controlled by traffic signals.
As of late 2002, work was complete on the New York side, leading to more exit weirdness. Matthew Dixon of Boston reports.
"For Thanksgiving, I travelled the Merritt Parkway en route to Pennsylvania. As you know, CT has been working on the parkway in Greenwich and NY has just finished rebuilding the Hutchinson River Parkway. This has resulted in some interesting signage at the 120A/King Street exit.
Travelling southbound, signs in Connecticut now exist for both exits. They refer to Connecticut's exit as 27 (not 27N) and to New York's exit as 27S. However, as soon as you cross into New York, you are greeted by not exit 27S but another exit 27! The NY ramp appears to have been modified to provide access to a side street rather than directly to 120A.
Also, the NY exit gore sign is smaller ("big exit 27" vs "little exit 27"?). Northbound, NY still does not provide signs for the CT exit. I don't remember if NY called it exit 27 or exit 30 northbound."
As of 2012, there's a left-turn channel from the Merritt Parkway southbound that is blocked off; traffic instead uses the New York-side loop of the interchange, which remains a (very fractured) cloverleaf.