5 miles per hour

A cop pulled over an old Buick on the 5 freeway which was driving extremely slow. She walked up to the Buick and there were three old ladies in it. One was sitting in the front, the driver, looking angry, and the other two were sitting in the back crying and shivering...
The cop asked the driver why was she driving so slowly. The old lady answered angrily, "cuz that sign on the sides of the freeway says 5 miles per hour!"
"No, no, no, that was just the freeway number," said the cop. After giving the poor lady a warning, the cop was curious and asked, "By the way, why are the old ladies in the back crying so hard?"
The old driver said, "Cuz we just came off the 118 freeway."