Perhaps when I used the word ‘prohibits’, it was a little misleading. Auto locking is apparently permitted as long as there is an approved mechanism also in place to unlock the doors in the event of an accident.The complexities of achieving that mean that most manufacturers choose to omit auto-locking entirely.
The offending regs are UNECE regulations R94 and R95, with full compliance by manufacturers being required by mid 2015.
The following is an extract from an article published in 2014 on Lifedrive.com (therefore are not my words), but said article is no longer directly available.
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The Regulations
The regulators at the WP.29 have determined that vehicle crash testing must be done with the doors closed but not locked. After the impact, the doors must be able to open normally without any special tools.
A spring-pull device is used to measure the force required to open the doors, it must not be more than 500 Newton. The rationale behind this is that the vehicle occupants must be able to free themselves without any assistance.
So the question is: how does one determine that the doors can still be opened after an impact? Well, since no sane person will want to sit inside a crash test car, nor is putting an indestructible robot inside practical, opening the doors will have to be done from the outside. Hence, the test protocol stating that the doors on the test car must not be locked when the vehicle was set in motion.
Standardized testing must accommodate the lowest common denominator. The way the regulators see it, testing with the doors unlocked is the most logical approach as in most countries, automatic door locks are an optional item.
Realizing that the existing test protocols are not a good representation of actual driving conditions (drivers may manually lock the doors), OICA, the International Organization of Motor Vehicle Manufacturers is proposing to amend the existing test protocol to allow an option for manufacturers to demonstrate:
a) In the case of vehicles equipped with an automatically activated door locking system, the doors must be locked before the moment of impact and be unlocked after the impact.
b) In the case of vehicles equipped with automatically-activated door locking systems which are installed optionally and/or which can be deactivated by the driver, the absence of the system or when the system is de-activated, no locking of the side doors shall occur during the impact.
However this is still at a proposal stage.
What’s On The Market
To comply with existing UNECE regulations, vehicles that feature the automatic door-lock feature must also include a mechanical release mechanism that unlocks all doors in the event of a serious accident. This device is not as simple as it sounds and the after-market solutions sold by your local accessories shops are not likely to measure up to the required standards.
The release mechanism is a very critical safety device and it is designed to only release the locks after exceeding a certain impact force threshold. It needs to be rigorously tested and certified that it will continue to work even when subjected to extremely strong impact forces.
Also, many modern cars are designed to disconnect the vehicle's battery in the event of a serious collision. For an impact sensing automatic door unlock feature to work, it would need to have a separate battery to continue powering the mechanical release.
This implies additional cost, far more than what your local accessory shop's uncertified solution will cost you.
Thus explains the deletion of automatic door lock features in many new cars on the market today. Premium brands usually offer the feature as standard.
Still, the feature is not a preserve of luxury cars. Kia for example, equips its Cerato with automatic door locks with an impact-sensing automatic unlocking feature.
Some manufacturers may go one step further and integrate the impact-sensing automatic door unlocking feature with other safety features. Volkswagen ICRS (Intelligent Crash Response System) for example, will unlock all doors, activate hazard lights and disable the fuel pump once the seatbelt pretensioners activate, or airbags are deployed. The feature is also available on the entry-level Polo Sedan and Polo hatchback.
In meantime, drivers will have to weigh the probabilities between getting trapped inside a car versus being carjacked.
