对于在国内大中城市中高速公路里程最长、立交桥最多的北京来说，目前的交通状况是窘迫的。 从 80年代中期以来，这个城市一次次向交通堵塞发起挑战，但似乎立交桥建得越多，车就堵得越厉害。近几年，一些立交桥上面纷纷竖起了红绿灯，完全没有了立交的感觉。“安定门立交桥， For Beijing, which has the longest mileage and the overpass in medium and large cities in China, the current traffic situation is distressing. Since the mid-1980s, the city has challenged traffic jams time and again. However, it seems that the more the overpasses are built, the more vehicles are blocked. In recent years, some of the overpasses have been put up above the traffic lights, there is no feeling of interchange. "Andingmen overpass,