Hit the road. 上路了

A: Do you want to come in for some tea?
A: 你要不要进来喝个茶呢?
B: No. I'm running late. I really need to hit the road.
B: 不了。我快迟到了, 得上路了。

"running late" 是快迟到了的意思。
"Hit the road" 的 "hit" 有「去」的意思。好比某人每周去健身房三次, 你就可以说 "He hits the gym three times a week."。
"I really need to hit the road." 还可以用说成"I really need to get going."。