Tom Day, age 10, of Spokane, Wash., for his question:
HOW MANY ROADS ARE THERE IN THE UNITED STATES?
Busiest stretch of road in the world is the Don Ryan Expressway in Chicago between 43rd and 47th streets, where 254,700 vehicles pass each day. Setting a 24 hour average on Fridays in 1974 was the interchange of the Santa Monica and Harbor freeways in Los Angeles. This busy section of roadway saw 425,000 vehicles pass each day.
Roads and highways between our towns and cities form vital lifelines. The farmers use them to move their products to the markets, and manufacturers use them to distribute their items. Millions of cars and trucks move across our highways and avenues each day on missions of business and pleasure.
There are 3,800,000 miles of graded roads in the United States. Canada has about 450,000 miles of roads and highways.
More than three quarters of all the roads in the United States are local and secondary streets. Local roads carry traffic within a metropolitan area, while secondary roads connect local roads to main highways. Local governments, such as counties and towns, build and maintain the nation's network of secondary and local roads.
A federal interstate highway system measuring 42,500 miles is now being completed. Officially called the National System of Interstate and Defense Highways, the network of highways will connect more thAn 90 percent of the cities in the United States with populations over 50,000 when completed. Experts figure that about 20 percent of all traffic in the country will move over this important system.
Highways and their continuations through towns are numbered by the states and are marked with black and white shield shaped " U.S. " signs. Interstate highways are marked with red, white and blue shield shaped signs.
In the " U.S. " and interstate system of numbering highways, routes which run east and west have even numbers while those running north and south have odd numbers. The lowest numbered " U.S." routes are found in the North and the East while the lowest numbered interstate networks are found in the West and the South.
Experts agree that most highway lanes should be at least 11 feet wide, and this is the standard used on most new construction. Engineers have also established standards of paving thickness and the kind of foundation and surfaces which work best. They've also determined how sharp curves should be and the maximum steepness of hill highways. Before a new road can be built or an existing one rebuilt, extensive planning is necessary.