Police stopped and old gentleman

Police stopped and old gentleman on the M8 who was travelling really slowly.
As they approached the car they noticed and old lady sitting in the passenger seat, eyes wide and staring, mouth wide open and clutching the dashboard so hard that her knuckles were white.
"Why did you stop me?" asked the old man.
"Well sir you were going a bit slow and causing a hazard to other motorists."
"Well I think you are bang out of order officer. I have been driving for fifty five years, never had and accident or even a parking ticket. How have I done this you ask, well, I'll tell you young man. I obey the law and the rules of the road. I'm on the M8 so I'm travelling at eight miles an hour."
"Sir, the M8 is just the name of the motorway. You may travel up to 70mph on this road."
Looking at the old lady in the passenger seat the officer asked, "Is your companion alright sir?"
"Oh just ignore her son. She's been like that since we came off the A125."