Pan-American Highway
The Pan-American Highway is a network of roads stretching across the American continents and measuring about in total length. Except for a rainforest break of approximately , called the Darién Gap, the roads link almost all of the Pacific coastal countries of the Americas in a connected highway system. According to "Guinness World Records", the Pan-American Highway is the world's longest "motorable road". However, because of the Darién Gap, it is not possible to cross between South America and Central America with conventional highway vehicles. Without an all-terrain vehicle, it is necessary to circumnavigate this terrestrial stretch by sea.
National Highway System (United States)
According to the Federal Highway Administration, the National Highway System includes roads important to the United States' economy, defense, and mobility, from one or more of the following road networks (specific routes may be part of more than one sub-system):The system includes 4% of the nation's roads, but carries more than 40% of all highway traffic, 75% of heavy truck traffic, and 90% of tourist traffic. All urban areas with a population of over 50,000 and about 90% of America's population live within of the network, which is the longest in the world.