Harassenger (blend of harass and passenger) is a passenger who is constantly judging your driving skills. He/she constantly cautions you to keep a safe distance from the car in front of you, checks that you're obeying the speed limit, and is always quick to point out your navigational errors.

Harassenger（harass和passenger二词的合成形式）指坐在你车上并不停对你的驾驶技术挑毛病的乘客，我们可称为“恼人乘客”。他/她会不停地提醒你与前车保持安全距离，查看你的车速是否在限速范围内，而且总能很快指出你的导航错误。

For example:

Guy riding shotgun: "Could you slow down a little? We're dangerously close to exceeding the speed limit by 5 mph."

副驾驶座位上的乘客：你能不能开慢点儿？我们很快就要超速5迈了。

Driver: "Quit being such a harassenger."

司机：你快别烦我了！