From the ArcaMax Publishing, Jokes Newsletter:
http://www.arcamax.com/news/jokes/s-385235-831325
A few years ago the battery in my beat-up VW Beetle had died because I
left the lights on overnight. I was in a hurry to get to work on time
so I ran into the house to get my wife to give me a hand to start the
car. I told her to get into our second car, a prehistoric oversized
gas guzzler, and use it to push my car fast enough to start it.
I pointed out to her that because the VW had an automatic
transmission, it needed to be pushed at least 20 mph for it to start.
She said fine, hopped into her car and drove off. I sat there fuming
wondering what she could be doing.
A minute passed by and when I saw her in the rear-view mirror coming
at me at about 30 mph, I realized that I should have been a bit
clearer with my directions.