But variables like pedestrians in crosswalks, large crowds and vehicle wrecks can throw a carefully designed system out of whack, leading to annoying and pollution-causing traffic jams.

但是，正在穿越人行横道的路人、摩肩接踵的人群以及道路上抛锚的事故车等不确定因素都可能让一套精心设计的系统崩溃失常，导致恼人而又产生污染的交通拥堵。