The predominant form of transportation in Houston is the automobile with 71.7 percent of residents driving alone to work This is facilitated through Houston's freewaysystem, comprising 739.3 miles (1,189.8 km) of freeways and expressways in a ten-county metropolitan area. Its highway system uses a hub-and-spoke freeway structure serviced by multiple loops. The innermost loop is Interstate 610, which encircles downtown, the medical center, and many core neighborhoods with around a 10-mile (16 km) diameter. Beltway 8 and its freeway core, the Sam Houston Tollway, form the middle loop at a diameter of roughly 25 miles (40 km). A proposed highway project, State Highway 99 (Grand Parkway), would form a third loop outside of Houston. As of 2010, only two out of eleven segments of State Highway 99 have been completed. Houston is located along the route of the proposed Interstate 69 NAFTA superhighway that would link Canada, the U.S. industrial Midwest, Texas, and Mexico. Other spoke freeways either planned or under construction include the Fort Bend Parkway, Hardy Toll Road, Crosby Freeway, and the future Alvin Freeway.
Houston's freeway system is monitored by Houston TranStar—a partnership of four government agencies that are responsible for providing transportation and emergency management services to the region. Houston TranStar was the first center in the nation to combine transportation and emergency management centers, and the first to bring four agencies (Texas Department of Transportation, Harris County, Metropolitan Transit Authority of Harris County, and the City of Houston) together to share their resources.
The Metropolitan Transit Authority of Harris County (METRO) provides public transportation in the form of buses, light rail, and lift vans. METRO's various forms of public transportation still do not connect many of the suburbs to the greater city. METRO began light rail service on January 1, 2004 with the inaugural track ("Red Line") running about 8 miles (13 km) from the University of Houston–Downtown (UHD), which traverses through the Texas Medical Center and terminates at Reliant Park. METRO is currently in the design phase of a 10-year expansion plan that will add five more lines to the existing system.
Amtrak, the national rail passenger system, provides service to Houston via the Sunset Limited (Los Angeles–New Orleans), which stops at a train station on the north side of the downtown area. The station saw 14,891 boardings and alightings in fiscal year 2008.
Houston is served by three airports, two of which are commercial that served 52 million passengers in 2007 and managed by the Houston Airport System. The Federal Aviation Administration and the state of Texas selected the "Houston Airport System as Airport of the Year" for 2005, largely because of its multi-year, $3.1 billion airport improvement program for both major airports in Houston. The primary city airport is George Bush Intercontinental Airport (IAH), the eighth-busiest in the United States for total passengers, and sixteenth-busiest worldwide. Bush Intercontinental currently ranks third in the United States for non-stop domestic and international service with 182 destinations. In 2006, the United States Department of Transportation named George Bush Intercontinental Airport the fastest-growing of the top ten airports in the United States. Houston is the headquarters of Continental Airlines and Bush Intercontinental is Continental Airlines' largest hub. The airline offers more than 700 daily departures from Houston. In early 2007, Bush Intercontinental Airport was named a model "port of entry" for international travelers by U.S. Customs and Border Protection. The Houston Air Route Traffic Control Center stands on the George Bush Intercontinental Airport grounds. The second-largest commercial airport is William P. Hobby Airport (named Houston International Airport until 1967) which operates primarily small to medium-haul domestic flights. Houston's aviation history is showcased in the 1940 Air Terminal Museum located in the old terminal building on the west side of the airport. Hobby Airport has been recognized with two awards for being one of the top five performing airports in the world and for customer service by Airports Council International. Houston's third municipal airport is Ellington Airport (a former U.S. Air Force base) used by military, government, NASA, and general aviation sectors.