Why Can't You Open Your Car Door If Someone is Trying to Unlock It at the Same Time?

At some point, everyone who rides in a car will experience the same awkward dance between a passenger and a driver: the door unlocking kerfuffle. One person pushes the button to try to unlock the car, while the person trying to get the door open pulls the handle at the same time. The car won’t unlock, and both passenger and driver have to repeat the process all over again—perhaps going through the whole procedure multiple times before successfully getting the timing right. Shouting may ensue.

According to Jalopnik, this inconvenient feature of all cars is the result of the very complicated mechanics behind automobile doors. To explain how, Jalopnik senior editor Jason Torchinsky and writer David Tracy opened up the door panels on two cars to see how each locking mechanism worked.

The simple answer is that the unlock button and pulling the door handle both trigger two different actions inside the door. “The most basic explanation possible is that pulling on the handle engages a little mechanical piece inside the door, a piece that bumps into another mechanical piece triggered by someone else trying to unlock the door,” Torchinksky and Tracy write. “Alone, either one would do their job unimpeded. Do both at the same time and they block each other.”

This is true in both older cars and newer models, though the latch systems have evolved over the years. These door locks include multiple links and latches that each have to coordinate to lock and unlock a car. Because the system that unlocks the door from the inside with a button and the system that unlocks it from the outside with a key are completely separate, they can’t both be engaged at the same time—kind of like how you can’t breathe and swallow at the same time.

For a closer look, you can see a door lock in action for yourself in this breathlessly narrated but useful YouTube video illustrating how the locks on a 2001 Toyota Corolla work.

If you’re mechanically inclined, head to Jalopnik for more details, including photos and graphics that allow you to see inside doors and get up-close with the locking mechanisms.

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