Emergency ambulance on route to a call, UK. This particular vehicle is operated by the West Midlands Ambulance Service NHS Trust and is a typical road ambulance based on the chassis of a van. There are many different types of ambulance, this is an emergency ambulance used for the treatment and transportation of patients requiring emergency care for critical life-threatening conditions. The word ambulance is said to derive from the Latin word "ambulare" which is translated as to walk or move. Wagons carrying the sick and injured were referred to as ambulances in the late 19th Century.