In the US, there are four types of new and used ambulances. There are Type I, Type II, Type III and Type IV. Type I is based upon a heavy truck chassis and is used primarily for Advanced Life Support and rescue work. Type II is a van based ambulance with little modifications except for a raised roof. Its use is for basic life support and transfer of patients. The Type III is a van chassis but with a custom made rear compartment and has the same use as Type I ambulances. Type IV’s are nomenclature for smaller ad hoc patient transfer using smaller utility vehicles where passenger vehicles and trucks would have difficulty in traversing, such as large industrial complexes, commercial venues, and special events with large crowds.