A policeman noticed that a car was driving very slowly on the highway. He stopped the car and looked inside. He saw 5 old ladies, all were shaken up and seem to be very scared except for the driver. The officer and the lady driver had the following chat:

Officer: You are driving too slow. Slow drivers are just as dangerous as fast drivers.

Driver: Officer, I am not driving too slow. I always drive the exact speed limit. The sign says 15 and I am driving 15 miles/hour.

Officer: Lady, this is the rout number not the speed limit!

Driver: Oh, I am so sorry officer, I must be confused.

Officer: What’s wrong with your friends? are they alright?

Driver: Yes, they’re fine. We just got off rout 120.