Pan American highway

Pan American Highway is a system of highways that extends from the United States-Mexican border to southern Chile. It also connects the east and west coasts of South America, and links the capitals of 17 Latin-American countries. The 29325-mile (47,516-kilometer) system benefits Latin America's economy. It provides a route for raw materials and agricultural products through much of Latin America. The Pan American High­way is sometimes described as running through the western United States and Canada up into Alaska. But neither country has officially named any highway as part of the Pan American Highway system.

Route. The Pan American Highway has four major U.S. terminals: Nogales, Ariz.; and Eagle Pass, El Paso, and Laredo, Tex. It crosses Mexico, Guatemala, El Salvador, Honduras, Nicaragua, and Costa Rica, and into Panama. The Darien Gap, a stretch of about 90 miles (140 kilometers) of jungle, blocks the highway at Yaviza, Panama. Motorists usually ship their cars from either Cristobal or Balboa, Panama, to Colombia or Venezuela. South of the gap the highway follows the western coastline of South America to Puerto Montt Chile.

At Santiago, Chile, about 660 miles (1,060 kilometers) north of Puerto Montt, a major branch of the highway cuts eastward across the Andes Mountains to Buenos Aires, Argentina. From Buenos Aires, it follows the east coast of South America north to Rio de Janeiro, Brazil, then turns inland to Brasilia, the capital of Brazil. Other branches of the highway lead to the capitals of Bolivia (La Paz and Sucre), Paraguay (Asuncion), and Venezuela (Caracas).

Development. The idea to link North and South America dates from the late 1800's, when people talked of building a Pan American railway. But it was not until 1923, at the Fifth International Conference of American States, that a highway was seriously considered. This conference led to the First Pan American Highway Congress at Buenos Aires in 1925.

Organization of the system started in the late 1920’s. By 1940, over 60 per cent of the highway between the United States and Panama had been completed. By the early 1950’s, most of the project was open to travel in South America. An important link in the system opened in 1962, when the Thatcher Ferry Bridge was completed over the Panama Canal at Balboa. The bridge is 1 mile (1.6 kilometers) long and is one of the world's longest steel arch bridges.

Each South American country has financed the building of the highways within its own borders. In 1930, the United States began giving financial support to speed the building of the Pan American Highway between Panama and Texas. This section is also called the Inter-American Highway. The United States has contributed two-thirds of the cost of building this part of the highway. Only Mexico has not used United States financial aid in building the system.

The Pan American Highway Congress, sponsored by the Organization of American States (OAS), meets every four years to discuss the development and progress of the highway system. The congress has headquarters in the General Secretariat of the OAS, Washington, D.C

KINDS OF ROADS AND HIGHWAYS (in America)

There are about 3,900,000 miles (6,200,000 kilometers) of surfaced and unsurfaced streets, roads, and highways in the United States. Canada has about 550,000 miles (885,000 kilometers) of surfaced and unsurfaced roads.

Local and secondary roads make up about 80 per cent of the roads in the United States. Local roads carry traffic within a local area. Secondary roads link small communities and connect local roads to main highways leading to more distant places. Most local and secondary roads are built and maintained by local governments.

Primary highways. The most important roads generally are those that carry the greatest number of automobiles, trucks, and buses. These main roads, called primary highways, connect the larger communities. Most are constructed and cared for by state governments.

The federal government helps the states pay the cost of building and improving primary and secondary roads and streets. The routes are selected by states.

Some highways with four or more traffic lanes are divided in the center with a strip of land, called a median strip. This separates lanes of traffic going in opposite directions and helps prevent collisions.

Another important factor in safety and smooth traffic flow is the principle of controlled access. On fully controlled access highways a vehicle can enter or leave a main highway only at certain locations called interchanges. These interchanges are usually located at main crossroads. Grade separations are often used to separate crossing streams of traffic. In a grade separation one of the intersecting highways crosses over the other on a bridge. The two are connected by sloping, curved roadways called ramps.

With controlled access, no driveways from homes or commercial establishments connect directly with the main highway. Minor roads and streets run over or under the road without connecting to it. Minor roads may also dead-end at the highway or connect with a service road that runs parallel to the highway.

Freeways are main highways with full access control and grade-separated interchanges. Those with four or more lanes are divided by a median strip. Freeways in congested parts of big cities are often elevated (built above surface streets) or depressed (built below surface streets). The term freeway refers only to the free flow of traffic. Motorists may have to pay a toll to travel on these roads.

Expressways are similar to freeways but sometimes have only partial access control. Parkways are roads resembling freeways. But they are built in parklike surroundings with attractive landscaping and scenery. Most parkways are limited to passenger cars.

Bypasses are built to take motorists around cities. Motorists traveling some distance often do not want to drive through small towns or centers of large cities that lie on their routes. Those traveling from one part of a city to another also usually prefer to avoid downtown traffic. The bypass helps these motorists avoid city traffic, and reduces traffic congestion for those who want to drive into town.

Bypasses today are usually built as freeways, sometimes with service roads on one or both sides to serve local traffic.

Intersections are crossings of one road by another. Most intersections are at the same level, so that vehicles going east or west have to take turns crossing with vehicles going north and south. Sometimes roads intersect at odd angles and it is especially difficult to make a safe crossing. At such places the engineer may put islands in the paved area to keep traffic in the proper paths. When two freeways intersect, more complex interchanges are sometimes needed.

Дата добавления: 2015-10-30