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. Protecting Child Passengers
Each year, many children are injured or killed in vehicle crashes because
they are
either unrestrained or not properly restrained. In fact, vehicle crashes are the
number one cause of death of children ages 12 and under.
To reduce the number of child deaths and injuries, every state, Canadian ...