Everyone has seen them racing down the road at any hour with flashing lights and blaring sirens on the way to the hospital.

Because they are so commonly seen, ambulances have become a visually obsolete; what looks like a big box on wheels is actually a lot more complex than most think.

Here are four things you didn’t know about ambulances.

There are five different stretchers on the average ambulance:

When you hear the word stretcher, the first image that typically comes to mind is a long bed atop a set of wheels. Aside from that stretcher, somewhere inside the ambulance (the location varies by model) is a reeves, stair chair, scoop, and backboard. Each serves it’s own function.

The reeves is a plastic, flexible, stretcher that is used to move a patient through tight areas, like narrow stair ways. The reeves requires EMTs to carry the entire weight of a patient because it has no wheels.

A stair chair is exactly what it’s called: a chair a patient sits on to be brought down a flight of stairs. This is only used when the patient is in fair condition and can tolerate being moved in an upright position. The chair is attached to four wheels and a set of tracks that allows for the patient to easily and securely slide down the stairs.

A scoop is used for someone who cannot move from the position they are in or for someone who has a hip injury. This is a piece of metal that separates in half, allowing EMTs to “scoop” the patient up without having the physically move them at all.

The backboard is a solid piece of plastic that helps stabilize a patient with a head or neck injury. The patient is easily rested in a neck collar that is attached to the backboard. Using a backboard requires at least three people to help move the patient: one to hold the neck in place and someone on each side. It’s also often used for CPR, because it provides a firm surface for chest compressions.

An ambulance needs to charge:

Like your cell phone, an ambulance needs to be plugged in so it has enough power to run. Because of the amount of equipment, the battery needs a power source to stay functional unlike a regular car battery. Many ambulances also have a power outlet in the back of the ambulance.

Ford manufactures ambulances:

While an ambulance seems to look completely different than the average car or truck on the road, the actual vehicle isn’t too different. Ford is one of the United States leading ambulance producers, and if you look closely, the design and construction isn’t too different than an F150.

Different sirens don’t mean different things:

The honking tones change as responders rush down the road, but the meaning stays the same: get out of the way. EMTs use discretion on what sound to let out based on their own preferences, and sometime on how populated the area is at the time of emergency.

Next time you’re yielding to an ambulance, think about what may be going on inside, rather than the fact that your commute home just got 15 seconds longer.