trafficking的原形是哪個單詞

　　例句：

　　Traffic is bad, particularly in the city centre.

　　交通狀況很差，尤其是在市中心。

　　The traffic lights are controlled by a central computer.

　　交通信號燈由中心計算機(jī)控制。

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

　　交通嘈雜，我聽不見她的聲音。