There are two ways to exit Kennedy Airport, the JFK Expressway and the Van Wyck Expressway which is I-678.
If the bus driver had exited Kennedy Airport on the JFK Expressway and followed the signs East toward Long Island, he would have found himself on Conduit Avenue heading east. Once on Conduit Ave. this is the sign he would have seen at the entrance to the Belt Parkway. The Belt Pky in Queens becomes the Southern State Pky as it crosses into Nassau County. (Note this is from Google Streets, so the sign may have changed since this photo was taken.)
ON EDIT, I went back and looked again, there is another sign on the light pole on the left side of the ramp that says "No Trucks":
Had the driver left Kennedy Airport on the Van Wyck Expy (I-678) he would have seen these signs for the Eastbound Belt Parkway, note that there are 2 options for this exit.
Further ahead the roadway divides again, and this is where he should have seen that the parkway was a no-go and stayed on Conduit Avenue.
I grew up here and one of the first things you learn is "cars only on the parkway". I'm so used to it that I can;t be objective about the quality of the signs.
I was just reminiscing the other day about my grandfather who would visit from NJ and get mad about the parkways because they had no route numbers.
My Dad would give directions and say "Take the Southern State", and gramps would ask "What number is that?"
"It doesn't have a number, Dad, it's a parkway."
"Who the heck builds a road and doesn't put a number on it?!?!"
