A person with a medical certificate exempting them from using the vehicle's restraint systems, are they required to wear the seat belt fastened?

# Explanation When a person holds a medical certificate exempting them from using restraint systems, they are legally authorised not to wear the seat belt fastened. This certificate must be issued by competent health authorities and justifies an exception to the general mandatory rule. Therefore, they are not required to use the belt under any circumstances while the certificate remains valid.