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.

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. 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. 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.