The SRS system is also referred to as a passive restraint system because the vehicle occupants do not need to do anything in order to activate the SRS system when the enabling criteria—speed and deceleration—are met. In contrast, seat belts are an active restraint system. The vehicle occupants must proactively latch each seat belt in order for the seat belt to do its job. Even automatic seat belt systems have a lap belt that must be manually latched.