List of Interstate Highways in Utah
The Interstate Highways in Utah are maintained by the Utah Department of Transportation (UDOT). The Interstate Highway System is a nationwide system with only a small portion of these routes entering Utah. Originally, the State Road Commission of Utah, created on March 23, 1909 was responsible for maintenance, but these duties were rolled into the new UDOT in 1975. There are of Interstates within the state. The longest is Interstate 15 (I-15) at and the shortest is I-215 at . One unique former route is Interstate 415, which was never signed as such, and was only used as a temporary designation for the eastern portion of what is now the Interstate 215 belt loop around Salt Lake City.
California
The state has been a pioneer in road construction. One of the state's more visible landmarks, the Golden Gate Bridge, was the longest suspension bridge main span in the world at between 1937 (when it opened) and 1964. With its orange paint and panoramic views of the bay, this highway bridge is a popular tourist attraction and also accommodates pedestrians and bicyclists. The San Francisco–Oakland Bay Bridge (often abbreviated the "Bay Bridge"), completed in 1936, transports about 280,000 vehicles per day on two-decks. Its two sections meet at Yerba Buena Island through the world's largest diameter transportation bore tunnel, at wide by high. The Arroyo Seco Parkway, connecting Los Angeles and Pasadena, opened in 1940 as the first freeway in the Western United States. It was later extended south to the Four Level Interchange in downtown Los Angeles, regarded as the first stack interchange ever built.