衣食住行是国计民生的大事，道路交通是城市的血液。没有发达的交通道路，就没有发达先进的城市。北京城道路最初的街制，即大街宽24步；小街宽12步。过去大都是土道，北京的土质是所谓的黄土，地质脆弱，松散易干，黄土容易飞扬，降雨量不大，一直到解放前，也多半是土路。每 Basic necessities of life is an important event for people's livelihood, road traffic is the city's blood. Without a developed transportation road, there is no developed advanced city. Beijing City Road, the original street system, that is, 24 steps wide street; small street 12 steps. In the past, most of the earthwork was in the past. The soils of Beijing were so-called loess. The geology was fragile, loose and easy to dry, the loess was easy to fly and the amount of rainfall was small. Until the liberation, most of the soil was dirt road. each