From NYC or the west part of Long Island, LIHTI is approximately 50 miles east and is located on the campus of Stony Brook University. This is a approximately 70 minutes away but with traffic it can be more than 2 hours. Take the Long Island Expressway (LIE, I-495) eastbound from the Queens Midtown Tunnel in Manhattan or the Throgs Neck Bridge or Whitestone Bridge in Queens to exit 62 North (Stony Brook). Follow Nicolls Road (County Route 97) north for approximately nine miles. Go past the hospital entrance which is the first entrance. Turn right at the 2nd entrance which is the Stony Brook University East Campus (this is Health Sciences Drive) and LIHTI is the second building on the right; past a house that looks like a residence, the Clark House, and past a parking lot. Just after the curve you will see the entrance to LIHTI on your right. Park in a visitors parking spot and get a permit at reception desk for placing on your dash.
Car ferries cross Long Island Sound at two places; Bridgeport, Connecticut to Port Jefferson, New York (The Bridgeport & Port Jefferson Steamboat Co, http://www.88844ferry.com/
Take the Long Island Railroad (LIRR) Port Jefferson line from Pennsylvania Station in Manhattan to Stony Brook. The Stony Brook train station is at the north border of the Stony Brook University campus with bus service to the central campus provided. You can also walk but this will take approx 15 minutes (be sure to use the campus map below if you plan this). Some LIRR trains may require changing at Jamaica, or Huntington, or Hicksville Stations, so pay attention to instructions from the conductor. An alternative is the Ronkonkoma line since it has many more frequent trains but this will require a 20-30 minute local cab ride as well (additional expense and time).