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.
U.S. Route 20 (US 20) is an eastâwest United States highway. The 0 in its route number indicates that US 20 is a coast-to-coast route. Spanning 3,365 miles (5,415 km), it is the longest road in the United States, and the route roughly parallels that of Interstate 90 (I-90). There is a discontinuity in the official designation of US 20 through Yellowstone National Park, with unnumbered roads used to traverse the park. It and US 30 break the general U.S. Route numbering rules in Oregon, since US 30 actually starts north of US 20 and runs parallel to the north throughout the state.