Only three sections of the system are not part of the Interstate Highway System; these are the Garden State Parkway Connector in Rockland County, a 6 miles portion of the Berkshire Connector between its western terminus at exit 21A on the mainline near Selkirk and where it joins up with Interstate 90 at exit B1 near Castleton-on-Hudson, and a short section of the mainline within exit 24 in Albany that is located between where I-87 departs the roadway and I-90 enters it.