An overturned truck spilled tons of liquid chocolate across six lanes, blocking traffic in both directions.

一辆运送巧克力的卡车侧翻，大量的液体巧克力洒在了6条车道上，堵塞交通。

It means you drive slowly in every lane, block the highway and force the traffic to crawl along at a snail's pace.

也就是说，在每条车道上慢速开车，从而堵塞高速公路，迫使车辆以蜗牛般的速度缓慢前进。