Many passenger trains have toilet facilities, often at the ends of carriages. Toilets suitable for wheelchair users are larger, and hence trains with such facilities may not have toilets in each carriage.
Hopper toilet
The traditional method of disposing human waste from trains is to deposit the waste onto the tracks or, more often, onto nearby ground using what is known as a hopper toilet. This ranges from a hole in the floor to a full-flush system. The hole in the floor system is still in use in many parts of the world, particularly on older rolling stock. The principal disadvantage is that it can be considered crude or unhygienic and dangerous to health and the environment – it litters the railway lines and can convey serious health risks when the train passes over or under a navigable waterway. Passengers may be discouraged from flushing or using toilets while the train is at a station or standing at a red signal. To enforce this limitation, toilets may be automatically locked when the train pulls into a station or stops at a red signal. In the United States, railway employees were required to lock the toilets closed whenever a passenger train stood in a station or at any other location designated by instructions in the timetable. Toilets would promptly be unlocked upon departure. Properly-designed drop chute toilets will draw air like a chimney, pulling air through the lavatory door vents and down and out through the toilet, reducing odor. Hopper toilets are similar to old-fashioned sea toilets in that they release the excreta directly to the environment, untreated. In the UK, at the end of 2019, hopper toilets on timetabled passenger services remained in use. A plan to protect all rail workers and reduce public health risks was delayed with several operators applying for waivers.
Chemical holding tanks are usually included on newer carriages and railcars in wealthier and more densely populated parts of the world. One issue is that the tanks need to be regularly emptied, often at a terminal station or prolonged stop-over. If a train needs to be used again quickly, the tanks may not get emptied. In this case, toilets may back up, which can result in toilets being closed.
Vacuum toilet
used in the newest carriages are similar to those in airliners: waste is pulled into a holding tank with a high pressure pump. Their disadvantages are the same as of chemical holding tanks, in addition they require stable power supply for working, and flushing of anything else but water and human waste can easily break the pump.
Composting toilet
Some trains may have composting toilet tanks, which use bacterial action to break down solid and liquid waste. Only the broken down clean liquid is released to the trackbed after sterilisation. The solid waste only has to be emptied every half year. This type of toilet is in use in some trains in the Netherlands and Switzerland.
Cultural references
In the United States, Dvořák's tune "Humoresque Number 7" became the setting for a series of mildly scatological humorous verses, regarding passenger train toilets, beginning: In The Good Soldier Svejk, author Jaroslav Hašek used hypocatastasis to indicate the fruit of hopper toilets, while conveying soldiers' envy and contempt for their general officer: A popular Russian internetrunning joke and one of the most popular Yandex search requests is "what would happen if you dropped a crowbar into a train toilet at full speed?"
