Transportation in New York City City and Fort Lee, New Jersey, is the world's busiest bridge in terms of vehicular traffic. New York has historically been a pioneer in tunnel construction. Most carry rail lines, but there are four exceptions. The Lincoln Tunnel, which carries 120,000 vehicles per day under the Hudson River between New Jersey and Manhattan, is the world's busiest vehicular tunnel. The Holland Tunnel, also under the Hudson River, was the first mechanically ventilated vehicular tunnel in the world and is considered a National Civil Engineering Landmark by the American Society of Civil Engineers. Two other notable tunnels connect Manhattan to other
Boroughs of New York City River, and during the Dutch colonial era, was under the jurisdiction of New Amsterdam and known as Bergen. Jersey City and Hoboken in Hudson County, New Jersey, are sometimes referred to as the sixth borough, given their proximity and connections by rapid transit PATH trains. Fort Lee, New Jersey, in Bergen County, opposite Upper Manhattan and connected by the George Washington Bridge, has also been called the sixth borough. Miami and nearby areas in Florida, Philadelphia and China are locales entirely outside the city's metropolitan area which have been called New York City's sixth borough. Boroughs of New York City