These look like tiny cages on wheels for little kids.
In Japanese they’re referred to as お散歩カー/o-sanpo cars.
散歩/sanpo means “walk”.
They often use these carts to herd the kids out to a safe place to go for a walk.
They’re often used at preschools, which are called in 保育園/houikuen Japan.
It’s a novel idea but I feel sorry for the teacher trying to push a concentrated ball of toddler energy around the street.