在海峡、海湾一些狭窄的地方,人们由于“一水之隔”无法往来。为了解决这种横跨海峡、海湾的交通问题,同时又不妨碍海峡、海湾中船只的正常航行,人们便在海底下面建造一种人工隧道,这就是海底隧道。海底隧道既可以通汽车,也可铺设铁轨通火车,为隔海地区的铁路干钱、公路干线的连接提供了 In the Straits, some narrow bay, people can not get in because of “a water”. In order to solve this traffic problem across the Strait and the Bay, without hindering the normal navigation of ships in the Strait and the Gulf, people build an artificial tunnel under the sea, which is the Cross Harbor Tunnel. Cross-harbor tunnel can pass both cars, rail transit train can also be laid, for the railway across the sea dry Qian, highway link provided