Bus toilet

A bus toilet is a toilet onboard a bus that is usually a type of a vaccum toilet. It is most commonly found on intercity buses/coaches suitable for mid- or long-distance travel.
Many think that the toilet onboard a bus is only for peeing, but it can also be used for defecating. Due to the toilet's small opening, feces might not go down through the small hole on the toilet.
How a Bus Toilet Works.
A bus toilet works differently than a home toilet does. A bus toilet does not use water, and it is not hooked up to a sewer. On a bus, urine and feces are held in a holding tank. Bus toilets use a blue formaldehyde product to mask the odor of urine and feces.
There are two main types of bus toilets. One type has flap in the toilet that closes to hide the view of the holding tank. The other type does not have the flap, which leaves the holding tank in view.