他在突破警戒线后被一名警察拦截了。He was rugby tackled by a policeman after breaking through police lines.一列拖拉机突破了警戒线，隆隆响着驶上了高速公路。A line of tractors rumbled onto the motorway through a cordon of police.矿工们手持棍棒冲过了警戒线。The miners were armed...

“警戒线”的英语可以翻译为：[法] cordon，picket line ...