Background: Emergency Vehicles. In current law, authorized emergency vehicles include vehicles of any fire department, police department, sheriff's office, coroner, prosecuting attorney, Washington State Patrol (WSP), ambulance service, and any other vehicle authorized by WSP. Authorized emergency vehicles must be equipped with a siren audible from, and at least one light visible from, at least 500 feet away. When responding to an emergency, authorized emergency vehicles are also allowed to use signal preemption devices to allow the emergency vehicle the right-of-way. They may also not break some traffic laws, including proceeding past a stop sign, exceeding speed limits, and disregarding regulations governing direction of movement, among others.