Child-security locks

Child-security locks, more commonly known as child locks, are a simple mechanical or electronic safety feature that disables the interior handles of a car's rear doors so that they cannot be opened from inside. Their purpose is to prevent a child seated in the back from inadvertently or deliberately opening a door while the vehicle is in motion or stationary in traffic, a situation that could result in the child falling out, stepping into the path of passing vehicles, or being struck by traffic when alighting on the road side.

The traditional implementation is a small lever, dial or rotary slot located on the shut face of each rear door, visible only when the door is open. Moving this lever to the locked position mechanically decouples the inner door handle from the latch mechanism, so that operating the handle from inside achieves nothing. The setting is independent for each rear door and remains engaged until manually reversed. On many modern vehicles the function has become electronic, controlled by a button on the dashboard or driver's door panel that locks both rear doors simultaneously and may display a status indicator on the instrument cluster.

The essential design principle is that the locks affect only the interior handles. The exterior handles continue to work normally, so an adult can always open the rear doors from outside, and the central locking system operates as usual. This ensures that a child can be released by a parent reaching in, and it means the feature does not impede ordinary use of the vehicle by adult passengers entering from outside.

Child-security locks form part of a wider set of provisions for carrying children safely, alongside integrated child seats and the standardised ISOFIX and LATCH anchorage systems that secure child restraints rigidly to the body of the car. Whereas those systems address how a child is held in a crash, child locks address the everyday risk of a door being opened at the wrong moment. Many cars also offer rear electric window lockout for the same protective reasons.

There are important safety nuances. Because a child cannot open a locked door from inside, occupants must be released by someone outside, which has implications in an emergency such as a fire or a crash that incapacitates the driver. Rescuers and carers should therefore be aware of how the locks operate. The feature is most valuable for younger children and should be checked and engaged whenever they travel, but it is sensible to disengage it once back-seat passengers are old enough and responsible enough to operate the doors safely themselves.