Get to know your car’s locking system well to avoid inadvertently trapping someone inside.

The rate at which temperatures can rise inside a parked car on a hot or even just a warm day is the key reason for not leaving your loved ones – including your pets – locked in a parked car.

But there is another risk to consider before leaving anyone in a parked car.

A feature on some vehicles, which is intended to keep the vehicle itself safe, could unintentionally risk the safety of those inside it.

Cars that have a deadlock function can’t be opened from the inside when the deadlock is engaged. The doors simply won’t open from inside and can result in occupants becoming trapped in the car, unable to open the doors.

Hand on a car door handle

Also, with the ignition off, the powered windows won’t work. The system is designed to make the vehicle more difficult to break into, given the doors can’t be opened at all.

This can also mean that if anyone is inside, they won’t be able to get out when there are no windows down.

This is a common feature on some European cars.

In some instances, pressing 'lock' on the key fob twice in a row will deadlock the car making it impossible to open the doors using the internal door handles. On others, if a door is still open and the lock button is pressed on the key fob, the car will then auto-lock once the door is closed.

Car key remote on a car seat

Deadlock systems can sometimes be disabled, so that the deadlock aspect of the mechanism doesn’t function.

However, it may not be possible to disable deadlock systems on all vehicles, so it’s essential that owners are well aware of their vehicle’s capabilities in this area.

The best source of information about your vehicle’s door locking mechanisms will be in the owner’s manual.

Child in a car seat seen through a car window

With temperatures inside a locked car often soaring up to 40°C higher than the outside air temperature on a hot day, unintentionally trapping someone inside a car could be fatal.

As children are even more susceptible to heat stress, the risk of serious harm for them is even greater.

In some recent model vehicles, there is a rear-occupant alert function, which helps prevent drivers exiting when a rear passenger is left in the vehicle.

RELATED: What to do if your child is locked in your car »

Some late model cars also have a function that automatically locks the vehicle as you walk away from it with the key fob on you. This could be a problem if your intention was to leave the car unlocked for others to access, however it should be possible for drivers to disable this function.

Further, owners should also be aware of whether the child locks are engaged or not, as this will prevent the rear doors from being opened from the inside.

Hand on a child car lock

Tesla has an innovative way of addressing vehicle security through the use of Sentry Mode.

If someone leans on the car, according to Tesla, it enters an alert state and displays a message on the touchscreen warning that its cameras are recording. If someone breaks a window, Sentry Mode switches to an alarm state, which activates the car alarm and plays music at maximum volume from the car’s audio system.

All of which could be useful well before any deadlocking system is required.

We rescue more than 400 WA kids accidentally locked in cars each year

To avoid an accidental lock in, remember to keep your keys on you.

Find out more

Last updated February 2021