ring road       
noun [ C ] UK uk/ˈrɪŋ ˌrəʊd/ us/ˈrɪŋ ˌroʊd/ (US usually beltway)
 环路;环城路
a main road that goes around the edge of a town, allowing traffic to avoid the town centre
  We got stuck in traffic on the ring road. 我们在环城路上陷入了交通堵塞。 
 Compare: bypass noun