When a child is too big for a child seat, secure the child in a rear seat using the lap/ shoulder seat belt. Have the child sit upright and all the way back, then answer the following questions.

Checklist
If you answer yes to all these questions, the child is ready to wear the lap/shoulder seat belt correctly. If you answer no to any question, the child needs to ride on a booster seat until the seat belt fits properly without a booster seat.
Booster Seats

If a lap/shoulder seat belt cannot be used properly, position the child in a booster seat in a rear seating position. For the child’s safety, check that the child meets the booster seat manufacturer’s recommendations.
Safety of Larger Children
Protecting Larger Children-Final ChecksHonda Civic Owners Manual. Important Safety Precautions
Always wear your seat belt
A seat belt is your best protection in all types of collisions. Airbags are
designed to
supplement seat belts, not replace them. So even though your vehicle is equipped
with airbags, make sure you and your passengers always wear your seat belts, and
wear them properl ...