The United States is home to the largest passenger vehicle market of any country.

Overall, there were an estimated 250,851,833 registered passenger vehicles in the United States.

Overall passenger vehicles have been outnumbering licensed drivers since 1972.

In 2001, 90% of Americans drove to work in cars.

New York City is the only locality in the country where more than half of all households do not own a car (the figure is even higher in Manhattan, over 75%; nationally, the rate is 8%).

According to the US Bureau of Transit Statistics for 2006 there are 250,851,833 registered passenger vehicles in the US. Out of these roughly 251 million vehicles.

There were approximately 6,686,147 motorcycles in the US in 2006.

In 2005 the overall median age for automobiles was 8.9 years.

In the year 2006, 7,667,066 passengers cars were sold in the United States.

In 2006 923,000 vehicles were imported from Japan, making it the greatest exporter of vehicles to the US.

The network of highways, freeways, and expressways in the United States is called the Interstate Highway System.

The Interstate Highway System, as of 2004, had a total length of 46,837 miles (75,376 km), making it the largest highway system in the world.

Interstate highways usually have the highest speed limits in a given area.

Speed limits are determined by individual states.

Rural speed limits generally range from 65 to 75 miles per hour (105–120 km/h), although remote portions of Texas have speed limits of 80 mph (130 km/h).

Typically, lower speed limits are located in the northeastern states, while higher speed limits are located in the southern and western states.

Interstate east–west routes are assigned even numbers.

Interstate north–south routes are assigned odd numbers.

Odd route numbers increase from west to east with some exceptions.

Even route numbers increase from south to north with some exceptions.

Interstate route numbers divisible by 5 are generally main freeways carrying traffic long distances.

The most heavily traveled section of the Interstate Highway System is the 405 Freeway in Los Angeles, California, with a 2006 estimate of 390,000 vehicles per day.

The least traveled section of the Interstate Highway System is Interstate 95 just north of Houlton, Maine (near the Canadian border), with a 2001 estimate of 1,880 vehicles per day.

The most extreme directional points of the Interstate Highway system are:

• Northernmost: The northern termini of Interstates 5, 15, and 29, crossing the Canadian border at the 49th parallel near, respectively, Blaine, Washington; Sweetgrass, Montana; and Pembina, North Dakota.

• Southernmost: A bend on Interstate H-1 in the Kaimuki section of Honolulu, Hawaii, less than 1/2 mile (0.8 km) before its eastern terminus (lat. 21.3 deg. N.). The southernmost point in the 48 contiguous states is the southern terminus of Interstate 95 in Miami, Florida (lat. 25.8 deg. N.).

• Easternmost: The northern terminus of Interstate 95 near Houlton, Maine, at the border of New Brunswick in Canada (long. 67.8 deg. W.).

• Westernmost: The western terminus of Interstate H-1 in Kapolei, Hawaii (long. 158.06 deg. W.). The westernmost point in the contiguous states is a curve on Interstate 5 near Wolf Creek, Oregon (long. 123.23 deg. W.).

The highest point of the Interstate Highway System is at the Eisenhower Tunnel on Interstate 70 in the Rocky Mountains of Colorado, at the Continental Divide (elev. 11,158 ft/3,401 m).

The lowest point of the Interstate Highway System on land is on Interstate 8 at the New River near Seeley, California (elev. -52 ft/−16 m). The lowest point under water is on Interstate 95 in the Fort McHenry Tunnel under Baltimore Harbor in Baltimore, Maryland (elev. -107 ft/−33 m).

The longest east–west Interstate highway is Interstate 90, which runs 3,099 miles (4,987 km) between Boston, Massachusetts and Seattle, Washington.

The longest north-south Interstate highway is generally cited as Interstate 95; when completed, it will run 1,927 miles (3,101 km) between Miami, Florida and the Canadian border (there is a gap in New Jersey).

The shortest signed Interstate is Interstate 375 in downtown Detroit, Michigan, at 1.06 miles (1.71 km).

The shortest Interstate route segment within a state (or federal district) is I-95 in the District of Columbia which is 0.11 miles (0.18 km) long.

The section of Interstate 93 in New Hampshire that runs through Franconia Notch State Park is the only instance of a two lane highway, also called a Super-2 parkway, on the Interstate Highway System in the US.