They're common on highways in large cities in the US. They're supposed to be enforced through police. They'll give you a ticket if your caught not riding with

They're common on highways in large cities in the US. They're supposed to be enforced through police. They'll give you a ticket if your caught not riding with enough people in the car. The police rarely monitor it in the bay area, in my experience. Many people they don't meet the requirements ride in it anyway.