Stop arms designed for school buses and other vehicles where stop arms might be required or used as optional equipment. This product is mounted on the outside (driver side) of the vehicle and is used to stop traffic when bus doors are opened and occupants are exiting to cross the road. It is activated in conjunction with the overhead warning lights on school buses. (As well as various other means of activation on other types of vehicles.) SMI stop arms meet or exceed all OEM, North American Federal and State specifications, performance guidelines and functional requirements. Specific features and options listed below.