In the old days, my mother’s arm was the seat belt - remember when mothers stopped short and their arms would shoot out to prevent kids from heading into the dash?!
To the day she died, when Mom was in a car as a passenger, her arm would extend over whoever might be seated next to her - each and every time the driver would touch the brake pedal.
She had dementia, but this was one of those "it stuck" responses that never left her.
In the old days, for the old 2-door 1955 Chevy, my dad made a wooden car seat for the baby and all of us other kids had to sit squished in the back seat.
Which, in reality, would do nothing but cause her arm to be sandwiched between the kid and the dash in anything more than a low-speed crash.