The New Jersey Turnpike (or simply The Turnpike as it is known to New Jersey residents) is a toll road in New Jersey and is one of the most heavily traveled highways in the United States (according to the IBTTA, the turnpike is the nation's 5th most traveled highway). A majority of the mainline as well as the entirety of both extensions and spurs are part of the Interstate Highway System. Construction of the Turnpike from conceptualization to opening took 23 months, from 1950 to 1952. The Turnpike has 12-foot (3.7 m)–wide lanes, 10-foot (3.0 m)–wide shoulders, 13 rest areas named after notable residents of New Jersey, and unusual exit signage that was considered the pinnacle of highway building in the 1950s. The Interstate Highway System took some of its design guidelines by copying the Turnpike's design guidelines.