trafficking的原形是哪个单词

　　例句：

　　Traffic is bad, particularly in the city centre.

　　交通状况很差，尤其是在市中心。

　　The traffic lights are controlled by a central computer.

　　交通信号灯由中心计算机控制。

　　I couldn't hear her above the noise of the traffic.

　　交通嘈杂，我听不见她的声音。