Ambulances
In the United States, the 1973 National EMS Systems Act, which was passed by Congress in 1974, and implemented four years later (in 1978), required that communities receiving federal funds for their programs had ambulances that met new federal specifications. The regulations included minimum width and other requirements which virtually eliminated car-based vehicles. The last American-made car-based ambulance was built in 1978.
Most US ambulances are now defined by what are known as the "Federal KKK-1822 Standards." Designs based upon the cutaway van chassis with modular bodies are defined as Type III. (Type I uses pickup truck chassis and Type II are straight conversion of van with a raised roof rather than a modular body).
Many of these models have access between the driver and the patient care area, which for some applications, is a favorable feature over a full cab chassis with a modular box.
The same standards are practiced in Canada, but the legislation defining the types are provincially determined.
Read more about this topic: Cutaway Van Chassis