Five old ladies in the car

Sitting on the side of the highway, waiting to catch speeding drivers, a Police Officer sees a car puttering along at 22 KPH.
Says he to himself: "This driver is just as dangerous as a speeder!"
He turns on his lights and pulls the driver over.
Approaching the car, he notices that there are five old ladies in the car, two in the front seat and three in the back ... with eyes wide open and white as ghosts.
The driver, obviously confused, says: "Officer, I don't understand, I was doing exactly the speed limit! What seems to be the problem?"
"Ma'am," the officer replies, "you weren't speeding, but you should know that driving much slower than the speed limit can also be a danger to other drivers."
"Slower than the speed limit? - No sir, I was doing the speed limit exactly... Twenty-two kilometres an hour!" ... the old woman says a bit proudly.
The Police officer, trying to contain a chuckle explains to her that 22 is the highway number, not the speed limit.
A bit embarrassed, the woman grins and thanks the officer for pointing out her error.
"But, before I let you go Ma'am, I have to ask... is everyone in this car OK - because these women seem awfully shaken, and they haven't made a peep this whole time," 

The officer said. "Oh, they'll be all right in a minute officer. We just got off Highway 189."