A restroom on Amtrak's Acela Express.
(Ben Schumin, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons)
PASSENGER TRAIN TOILETS
Most passenger trains (usually medium and long-distance) have toilet facilities, often at the ends of cars. Toilets suitable for wheelchair users are larger, and hence trains with such facilities may not have toilets in each car.
Hopper toilet
A traditional method of disposing human waste from trains is to deposit the waste onto the tracks or, more often, onto nearby ground, using what was known as a hopper toilet. This ranges from a hole in the floor to a full-flush system (possibly with sterilization). The hole in the floor (also known as a drop chute toilet or direct flush toilet) 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 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 United States, Amtrak phased out its use of these toilets in the 1980s after waste from a Silver Meteor train crossing the St. Johns River in Florida, between Palatka and DeLand, landed on a fisherman who filed a lawsuit.
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.
In 2021, Indian Railways completed the phaseout of drop chute toilets, replacing them with indigenously developed bio-toilets. Apart from improving hygiene, the phaseout will save Indian Railways 4 billion rupees annually, due to the elimination of corrosion on the rails caused by human waste. They were replaced with bio-vacuum toilets, which use bacteria to decompose human waste, fulfilling a phaseout pledge made in 2010.
Chemical holding tank
Chemical holding tanks (retention 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
Vacuum systems 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 (e.g. toilet paper) 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 sterilization. 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.
A Passenger Train Toilet Gallery
This is one of several restrooms on the lower level of Amtrak Superliner No. 34960. (TJH2018, CC BY 3.0 US <https://creativecommons.org/licenses/by/3.0/us/deed.en>, via Wikimedia Commons)
A toilet on one of the FrontRunner trains. (Ben P L from Provo, USA, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons, cropped)
A sign posted on the toilet lid warns that lavatories in the Stadler KISS train cars are out of service during the Caltrain Electric Train Tour in San Jose, California, on July 29, 2023. (Minh Nguyen, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons)
Signs like this one were used on the Maine Central.
(Maine Central Railway, via W. Lenheim Collection)