Why does my car door unlock after I lock it?

When I rent cars (most recently, a Toyota Prius and a Ford Fusion), I'm frustrated because I'll lock the doors, both from the inside and from the key fob, but when I check to make sure that they're locked, they will unlock when I touch the handle.

What causes this? Do they unlock if the key fob is within a certain range?

When I lock the doors, I want them to stay locked!

Ford Fusion actually is a very smart car that can detect where the key fob is - whether it's inside or outside the car. Once you reach a certain proximity with the keys in your pocket, it will automatically unlock. If you check the Ford Fusion forums, lots of users find this helpful as you won't need to fumble for your keys during an emergency. I think the other cars you rented have the same feature. Just make sure to lock it completely and keep the key fob with you always.

In case you get locked out, just call a local locksmith in your area like atlantalockmaster.com. They can easily get to you in minutes and unlock your rented car safely.

I suppose that depends on what kind of car you're renting, and how the electronic door locks are set up. I'm sure that SOME newer cars ARE set up to unlock when the key fob is detected within a certain distance from the car.