一、问题的提出北京的道路,大部分为城区街道和环城快速路(如图),EG表示的中轴路和HF表示的长安街就属于城区街道,四边形ABCD与四边形abcd表示的三环路与二环路就属于环城快速路.走城区街道虽然路程短,但途中不免有堵车现象发生。再加上城区内有许许多多的 First, the issue of the proposed roads in Beijing, most of the urban streets and highway around the city (pictured), EG said the central axis road and Chang’an Street, represented by the HF belongs to the city streets, quadrilateral ABCD and quadrilateral abcd said three rings Road and the Second Ring Road belong to the Ring Expressway. Although the distance to the downtown area is short, there is inevitably a traffic jam on the way. Plus there are so many in the city