What are the rules on child car seats?

A child must use a correctly fitted child restraint until they are 135 cm tall or 12 years old, whichever comes first — and the more important point is that the legal minimum and the safest practice are not the same thing.

The two standards in use:

i-Size (R129), the newer regulation, based on the child's height, requiring rear-facing until at least 15 months, and including side-impact testing. Seats attach using ISOFIX.

R44/04, the older regulation, based on weight groups. Seats meeting only the withdrawn earlier versions must not be used.

Why rear-facing matters far more than people realise. A child's head is disproportionately heavy relative to a neck that is not yet strong, and in a frontal impact — the most common serious type — a rear-facing seat spreads the force across the whole back and head rather than loading the neck. Evidence from countries where extended rear-facing is normal supports keeping children rear-facing well beyond the legal minimum, commonly to age four.

The rules that are frequently broken unknowingly:

Never place a rear-facing seat in a front seat with an active airbag. This has been fatal. The airbag must be deactivated.

Backless booster cushions are now restricted for smaller children under newer approvals, because they provide no side protection and do not position the belt properly.

Coats and thick padding create slack — in a crash the padding compresses and the harness is effectively loose. Remove the coat, then add it over the top.

Second-hand seats should be avoided unless the full history is known, since a seat involved in a crash may be compromised invisibly.

Expiry. Plastics degrade, and seats carry manufacturer lifespans.

Fitting is where most failures occur. Checks repeatedly find a large proportion of seats incorrectly installed — loose belts, wrong routing, twisted straps. Free fitting checks are widely available and are worth using.

Exemptions exist for unexpected necessity, taxis and emergencies, and are narrower than assumed.

General information, not legal advice.