China's current Code for Design of Urban Road Engineering (CJJ 37-20 16) fully considers the position of roads in urban road network, traffic functions and service functions along the road, and divides urban roads into four grades: expressway, trunk road, secondary trunk road and branch road. The expressway here does not include the expressway. According to the road pavement, it is divided into asphalt pavement, cement pavement and block pavement, in which asphalt pavement and cement pavement are also called black pavement and white pavement. The design service life of each pavement varies from 30 years to 10 years, which is why urban roads always "dig-dig-dig"!
As a road serving the vehicle, its functions and requirements are far more than those mentioned above. It can be said that the automobile, which has been developing rapidly, is promoting the continuous development. The emergence of intelligent networking and self-driving cars will put forward revolutionary requirements for the transformation and upgrading of roads. It can be said that "if there is no back wave to push the front wave, how can we see the surge of the front wave!"