Speed limits in the United States vary depending on jurisdiction. Rural freeway speed limits of are common in the Western United States, while such highways are typically posted at in the Eastern United States. States may also set separate speed limits for trucks and night travel along with minimum speed limits. The highest speed limit in the country is , which is posted on a single stretch of tollway in exurban areas outside Austin, Texas. The lowest maximum speed limit in the country is in American Samoa. Alabama In Alabama, it is illegal to drive at a speed that is not "reasonable and prudent" for the current conditions and hazards. Drivers must also not drive so slowly that they impede the flow of traffic. If the speed limit is not otherwise posted, it is: in urban areas on unpaved roads on rural paved county roads on other two-lane roads on four-lane roads on Interstate Highways Trucks carrying hazardous materials are not to exceed . Alaska In Alaska, many of the major highways carry a speed limit, including: A majority of the Parks Highway between Fairbanks and Willow (excepting slower zones through Nenana, Denali Park, Cantwell, and Healy) Most of the Richardson Highway between Valdez and North Pole On the Glenn Highway, the freeway between Wasilla and Anchorage, and most of the west of Glennallen The Seward Highway in Anchorage between 36th Avenue and Rabbit Creek Road, and other non-freeway parts of the Seward Highway south of Bird Point Most of the Alaska Highway between the Canadian border and Delta Junction The Minnesota Drive Expressway features a speed limit, as does the Richardson Highway between Fairbanks and North Pole. Since the mid-1990s, Alaska's major highways have gradually been upgraded from 55 mph to 60 or 65 mph. However, several continue to carry the default speed limit, including: The Sterling Highway The Tok Cut-Off The Haines Highway Portions of the Parks Highway and Seward Highway designated "safety zones" Portions of the Elliott Highway and Steese Highway close to Fairbanks Engineering studies are needed to define which road segments to post a speed limit higher than . The Dalton Highway and parts of the Elliot Highway are 50 mph. Default speed limits in Alaska are: in alleys in a business district in a residential district on other roads The speed limit when towing a mobile home is . American Samoa The maximum speed