Seat belts and child seats: rules 99 to 102

Test yourself · 2

Two questions on child seats

Question 1 of 2

1. An 11-year-old child is 130 cm tall. You are taking them on a planned journey in your private car, with room for the correct child seat. What restraint must they use?

   • A An adult seat belt alone, because they are older than 3
   • B A suitable child car seat or booster seat Right
   • C An adult seat belt alone, because the journey is planned
   • D No restraint if an adult sits beside them in the rear

   The right answer is B: A suitable child car seat or booster seat

   WhyChildren normally need a child seat until age 12 or 135 cm tall, whichever comes first.

   Source: GOV.UK: Child car seats: the law - Using a child car seat or booster seat

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2. You need to take a 5-year-old child, 110 cm tall, on an unexpected, necessary journey over a short distance in your private car. The correct child seat is unavailable, but a rear seat has an adult belt. What does the stated exception allow?

   • A The child may use the adult belt on the rear seat Right
   • B The child may travel on the rear seat without any belt
   • C The child may share the driver's belt on the front seat
   • D The child may sit on an adult's lap without a belt

   The right answer is A: The child may use the adult belt on the rear seat

   WhyWith no suitable child seat, a child aged 3+ may use a rear adult belt on an unexpected, necessary, short trip.

   Source: GOV.UK: Child car seats: the law - Unexpected journeys, GOV.UK: Seat belts: the law - Overview

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The rule in plain words

You must wear a seat belt in a car, van or other goods vehicle if one is fitted (rule 99). The driver makes sure that every child under 14 wears a belt or sits in the right child seat. Passengers aged 14 and over are responsible for wearing their own belt.

A child under 1.35 metres (about 4 feet 5 inches) tall must use a baby seat, child seat, booster seat or booster cushion that suits their weight and is fitted the way the maker says (rule 100). GOV.UK puts the cut-off as 12 years old or 135 cm tall, whichever comes first. In the Highway Code’s words: “A rear-facing baby seat MUST NOT be fitted into a seat protected by an active frontal airbag”.

Who must wear what

Summary of the seat belt table under rule 99 of The Highway Code.

What it means in practice

An 11-year-old who is 130 cm tall

They have not reached 12 years or 135 cm yet, so on a planned journey they must use a suitable child car seat or booster seat.

An emergency, short trip with no child seat

If the right child seat is not available, a child aged 3 or older may use an adult belt in the back, but only if the journey is unexpected, necessary and over a short distance. A child under 3 may not travel without the right child seat, except in a licensed taxi or minicab, on a rear seat and without a seat belt (GOV.UK).

A rear-facing baby seat in the front

Only if the front airbag is switched off. A rear-facing baby seat must never go in a seat with an active frontal airbag: in a crash the airbag can seriously injure or kill the baby (rule 101).

Common mistakes

• Thinking older passengers are the driver’s problem. From 14, passengers are responsible for their own belt.
• Moving a child out of a booster seat too early. Wait until they are 12 or 135 cm tall, whichever comes first.
• Putting a baby seat in front of an active airbag. Switch the airbag off first, or use the back.
• Two people sharing one belt. GOV.UK says only one person may use each seat with a seat belt.
• Letting children sit in the boot of an estate or hatchback. Not unless a special child seat is fitted there (rule 102).

Questions about seat belts and child seats

Who is responsible for a passenger wearing a seat belt?

The driver, for passengers under 14. Passengers aged 14 and over are responsible for themselves. Source: rule 99.

When can a child stop using a car seat?

When they reach 12 years old or 135 cm tall, whichever comes first. After that they must wear a seat belt. Source: GOV.UK.

What is the fine for not wearing a seat belt?

Up to £500, and the same if a child under 14 is not in the correct car seat or wearing a belt while you drive. Source: GOV.UK.

Do you have to wear a seat belt when pregnant?

Yes, unless your doctor says you do not have to for medical reasons. Source: GOV.UK.

Read next

• Vehicle loading theory test questions
• Drink, drugs and tiredness: rules 91 to 96
• Mobile phones and driving: rule 149
• More Highway Code rules, explained

Sources

(3)

1. The Highway Code, rules 99 to 102 (seat belts and child restraints), GOV.UK. Checked 4 November 2026.
2. Child car seats: the law, GOV.UK. Checked 4 November 2026.
3. Seat belts: the law, GOV.UK. Checked 4 November 2026.

Contains public sector information licensed under the Open Government Licence v3.0. Quotes from The Highway Code are Crown copyright. Sources and image credits.