I always heard it called the "bitch test". If she doesnt open the door for you, then shes usually self centered and stuck up. Its excusable if shes doing something else at the moment, but its weird if shes just sitting there staring out the window. If she unllocks the door then it shows that shes thinking of you, or atleast really polite.
I've never used it as a test, but the results have usually been pretty accurate....i've always had better relationships with the girls that unlock the door.
Oh yeh, I dont have any power lock BS. Because I drive a classic Mustang.
