Deadlocks On Cars Are Poorly Understood And Can Kill If You’re Not Careful

Cars used to be simple, with manual locks on each door. Today, central locking systems have given us more convenience. But some of them have a largely unknown feature which can have terrible consequences. In some cars, it’s easy to lock people inside with no way to get out. It’s rarely seen in the US, but it’s common in Europe and the UK.

It’s actually shocking when you first encounter it. You’re locked inside a car, and no matter how much you tug on the handle or the locks, you can’t open the doors. You’re imprisoned. That’s because in certain vehicles, it’s possible to “deadlock” or “super lock” the vehicle, which can trap people if you’re not careful. They’ll be stuck inside with no escape, unless they’re rescued from outside or they manage to break a window.

Let’s look at how certain cars let you trap people inside, and why. And of course, most importantly, how you can avoid accidentally activating this oddball feature.

Why Does This Feature Even Exist?

So-called “Super locking” or “deadlock” features are intended as a security measure and are implemented by a wide range of automakers, including BMW, Subaru, and Honda.  The idea is that making the car impossible to unlock via the interior door handles and unlock buttons or tabs will prevent a thief from punching out a window and reaching through to unlock and open the door via the interior controls.

This locking mode is not intended to be used with people inside the vehicle, as they would be trapped inside and completely unable to get out of the vehicle short of breaking a window. But unless a vehicle has a safety system to sense occupants and prevent the mode from being activated, it’s very easy to accidentally deadlock a vehicle with the feature, leaving someone trapped inside.

In some cars, deadlocking is only activated if you double-press the lock button in quick succession. Some brands, however, activate it immediately even if the lock button is only pressed once. Thus, simply by locking the car and walking away, you could be activating the deadlock.

It’s a rare occurrence, but “deadlock” or “super locking” systems have claimed lives over the years. By making it impossible for someone inside the car to escape, they can succumb to dehydration or heat stroke on a warm day. Typically, we think of this as only affecting young children, as they aren’t old enough to figure out how to exit a vehicle on their own. However, in the case of a deadlocked or super-locked vehicle, even a healthy adult can struggle to escape, as the doors simply will not open from the inside.

Only a few vehicles sold in America have the feature. One notable case was covered by Sky News in 2013. The tragic incident in California saw Graciela Martinez die in her family’s BMW 328i. The 14-year-old student had been driven to school by her brother and decided to nap in the car before classes began. Her brother locked the vehicle for safety, not realizing she wouldn’t be able to unlock the car from inside. Nor could she honk the horn to attract help, as it was disabled by the vehicle under this condition. Her brother found her unresponsive when he returned to the vehicle after school.

The family eventually sued BMW over the matter, with ABC News later featuring stories of other individuals who had fallen victim to the same problem. At the time, BMW representatives noted a number of late ’80s and early ’90s vehicles had the feature. It’s now far less common on US market vehicles.

In spite of all this, the function is relatively common; it’s available on a wide range of modern European vehicles for a start. In these cars, it’s generally called “deadlocking.” In the case of UK market Hondas, it’s called “super locking.” It’s typically activated by pressing the lock button on the keyfob twice in quick succession. Alternatively, turning the key in the door to the locked position twice will do the same job.

As above, the UK market 2024 Honda CR-V owner’s manual states you should never activate Super Locking with people inside the vehicle. Under this condition, it becomes impossible to unlock the car from the inside. The only plausible escape is for the passengers to find a way to break the windows. Interestingly, the North American version doesn’t mention it—the feature is apparently absent in the US market model.

BMW has included the feature on some cars, as well, including in the United States. The manual for the 1997 BMW 328i explains how it works—and it’s even easier to activate. Simply locking the car with the keyfob makes it impossible to escape from the inside.

You can find deadlocks on cars from BMW, Kia, Honda, Subaru, Peugeot, Audi, and Volkswagen, among others. This isn’t an exhaustive list, either—you should read your owner’s manual and test the locking system yourself to determine if your car has this functionality.

It’s worth checking up on this on every vehicle you own. Forum posters have noted how traumatic it can be when they’ve inadvertently trapped their children in the car, even for just a few minutes. Others have posted about being trapped themselves, having to activate their car alarm to attract the attention of passers-by for a rescue.

Semi-Deadlocks Exist Too

My own 2008 BMW 320D has a similar feature. If the car is locked with the keyfob, none of the interior door handles will open the car. However, the E90 model does have a button on the dash that will unlock the doors from the inside. It’s still possible to trap people inside, however, because the button is not obvious (you can see it called out below). Unless the person who needs it knows it’s there, they may be unlikely to find and use it.

This feature isn’t universal among BMWs. Our own Thomas Hundal owns an E90 BMW of similar vintage to mine, and his doesn’t deadlock at all. Two tugs on the door handle, and you can pop right out of Thomas’s car. In mine, you’re stuck until you hit the button on the dash.

I was pretty surprised with this feature on the BMW. pic.twitter.com/rNGSgfv8Io

— Lewin S. Day (@rainbowdefault) April 9, 2024

Awareness Is Key

If you drive solo, deadlocks aren’t so dangerous. It’s rare that you’ll hit your keyfob’s lock button while you’re in the car. Even if you do, you can just hit unlock to free yourself, assuming the battery hasn’t died at that precise moment.

However, if you’re routinely driving with passengers, and especially children, you need to be very careful with deadlocks. You might think it’s safer to lock the doors to protect your passengers, but you might inadvertently be trapping them inside the vehicle. Read your manual, and understand how the locks work. Instead, it’s probably safer to have them lock the car from the inside so they won’t activate the deadlock system.

In some cases, automakers have made these systems safer over the years. Modern Mercedes-Benz vehicles tend to leave the horn enabled, for example. This lets you call for help if you’re stuck. Similarly, some modern BMWs with deadlocks at least provide a button that passengers can use to free themselves. But these features vary widely between vehicles and even the same cars sold in different markets, so check your own vehicles carefully.

Ultimately, it’s not always safe to lock a passenger inside a modern car. Even if they’re a fully-grown adult, they could be trapped inside. Make sure you know what you’re doing whenever you leave passengers in the vehicle!

Image credits: BMW, Mercedes-Benz, Honda, Peugeot