highway belongs to the high-grade highway . China's Ministry of Communications "Highway Engineering Technical Standard " stipulates that expressways refer to "roads " , which can adapt to the annual average day and night traffic volume of passenger cars of 25000 or more, and are specially used for cars to run at high speed and fully control access. Although countries have different names for expressways, they all refer to highways with more than 4 lanes, two-way separated driving, complete control of entrances and exits, and all three-dimensional intersections. In addition, many countries have direct trunk lines that partially control entrances and exits and not all use three-dimensional intersections, also known as expressways. In the annual statistical reports of the International Road Federation, the direct trunk line is also included in the category of expressways. The construction of expressways can reflect the degree of traffic development of a country and region, and even the overall level of economic development.

20 century 30 some western countries began to build, 60 since world countries highway highway has developed rapidly. The highway is an inevitable product of the development of the economy .

First, the highway adapts to the development of Industrialization and Urbanization . city is the gathering place of industry and population. its car grows much faster than the countryside and becomes the gathering center of cars. therefore, the construction of expressway starts from the city's ring road, radiation road and busy traffic section, and gradually becomes urban traffic with expressway as the backbone.

second, the development of automobile technology, objective requirements for the construction of highway . The car has become an indispensable vehicle in human society. Therefore, it needs the cooperation of infrastructure such as expressways. The lightness and load of the car are two major development trends. The former needs to increase the inner chain to ensure the speed of the latter, while the expressway can just combine the two organically. The rapid development of the automobile industry and the advancement of urbanization have brought great opportunities to highway companies. The transportation capacity of the main railway lines is tight, and the access channels in some areas are not smooth, and the expressways play an important role in transportation. Therefore, China's highway industry is in the period of industrial expansion, facing the opportunity of sustained prosperity.