Ambient noise includes all sounds present in an environ-. ment. The ambient noise level may be measured at any mo-. ment, but it will vary widely with time, e.g., with the coming. and going of trucks and aircraft. Traffic noise is higher at. noon than at midnight and higher still during the morning. and evening rush hours.
(According to the most recent U.S. numbered highway log, published in 1989 by the American Association of State Highway and Transportation Officials, the route is 3,249 miles long). In 1963, therefore, U.S. 20 became the longest road in the country. U.S. 20 is 3,365 miles long according to the 1989 log. The route begins in Boston at a junction with Massachusetts Route 2 and ends in Newport, Oregon, at a junction with U.S. 101.
Interstate 90 (I-90) The longest Interstate Highway in the U.S, this highway extends up to 3,099.07 miles (4,987 km). It runs parallel to the U.S Route 20 for the most part. Its eastern terminus is in Boston and western terminus is in Seattle. It crosses the Continental divide just east of Butte, Montana.