在城市里,成千上万辆汽车和自行车,在街上井井有条地行驰.驾车的司机,在交叉路口,服从交通警控制的红绿灯的指挥,因此,不致发生车祸事故.可是在海上或江河里情况就复杂多了,水底有浅滩、暗礁或障碍物;港内许多船只穿梭来往,航向交错不定,谁来有秩序地指挥繁乱的船舶安然通过呢?这就得依靠设在海上的“交通警”——航标来维持. In the city, thousands of cars and bicycles are well-lined up and down the street. Drivers who drive at the crossroads are subject to the Traffic Light Traffic Police command and therefore will not cause a car accident. However, at sea or in rivers The situation is much more complex, there are shallows, reefs or obstacles on the bottom of the water; many ships in the harbor are shuttling in and out of course, and who is going to order the chaotic ships in an orderly manner? It depends on “traffic at sea” Police "- beacon to maintain.