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美国现有公路总里程622万km,其中城市道路120万km,城间及乡村公路502万km.美国公路平均密度为每100(km)~2有66km公路,已形成千支相连、四通八达的公路系统.美国州际高速公路发展迅速,总长度达72448km,占全世界高速公路的2/3.美国高速公路系统总长度只占公路总里程的1.16%,却承担了全国公路运输任务的21%以上.美国州际高速公路设计标准,是基于研究当时公路的缺点,国防武器运输的需要以及和平时期交通流量而定.每条州际高速公路设计的远景规划是20年,按设计年份的第30个高峰小时交通量为准.设计标准包括三种行车速度(时速112km、96km和80km),每种行车速度具有不同的公路曲率半径、超高、视距和缓和曲线等因素.
The total length of existing U.S. highways is 6.22 million km, of which 1.2 million are urban roads and 502 million km of urban and rural roads. The average density of U.S. highways is 66 km per 100 km2, and thousands of links have been formed Highway Systems The U.S. statewide expressways have developed rapidly with a total length of 72,448 km, accounting for two-thirds of the world’s total freeways. The total length of the U.S. highway system is only 1.16% of the total length of the highway, but it is responsible for 21 % The design criteria for interstate freeways in the United States are based on the study of the then deficiencies of highways, the need for the transport of national defense weapons, and the traffic flow in peacetime. The long-term plan for each interstate freeway design is 20 years, The 30 th peak hour traffic volume prevails.The design criteria include three driving speeds (112 km / h, 96 km / h and 80 km / h), each with different road radius of curvature, superhighway, line of sight and easing curve.