In 1888, a German city built a railway that climbs without an onboard engine: 1,849 gallons of water weigh one car down enough to pull the other 272 feet uphill

Wiesbaden's Nerobergbahn has climbed the same hillside since September 25, 1888, and it has never used a motor to do it. Instead, it uses water. The technical specifications published by ESWE Verkehr, the transit company that has operated the railway under the city's public transit authority since it opened, confirm this. Every year, about 300,000 passengers ride two carriages that pull each other up and down a 272-foot rise using nothing but gravity and Wiesbaden's public water supply. The idea might seem too simple to work for a real train. But the Nerobergbahn remains Germany's oldest water-ballast rack railroad, and it still runs pretty much as it did in the days of Kaiser Wilhelm II.

How the water does the work

At the top station, one carriage fills a tank with water under its floor. The tank has a capacity of 1,849 gallons, or 7,000 liters, adding about 15,430 pounds to the carriage. Both carriages run on a steep 1,439-foot track and share a single steel cable that passes through a pulley at the top station. When the tank is full, the downhill carriage, which is heavier, begins to sink under its own weight. It pulls the cable as it falls, and the cable drags the lighter carriage up from the bottom. The route is mostly single track, with the two cars passing at a short loop halfway.


When the loaded carriage reaches the bottom, its tank is emptied. That water is kept in a 200-cubic-meter reservoir near the bottom station until a 37-kilowatt pump pushes it back up to a 350-cubic-meter tank at the top, ready for the next round trip. No part of the carriages' own cycle involves burning fuel, though the pump that returns the water to the top does draw electricity. The "no engine" design refers to the cars themselves, which carry no onboard motor.

A brake controls the ride

It's a common misconception that the train is pushed along by the toothed rail that runs down the middle of the track. It doesn't. That rack rail, based on a system devised by the Swiss engineer Niklaus Riggenbach, is only a brake and safety lock. The carriage's downhill speed is regulated by the operator, who changes the tightness of the gears engaging the rack.

Wiesbaden was not unique in this sort of engineering. Similar water-powered rack brakes were found on funiculars across Europe in the late 1800s, including Switzerland's Giessbach funicular, which opened nine years earlier, in 1879. A historical account of that separate railroad, published as an engineering landmark record by the American Society of Mechanical Engineers, describes how nineteenth-century engineers used a counterweighted, cable-connected carriage system to solve the same basic problem: moving a heavy carriage down a steep slope without letting it run away.

Built for a spa town that valued clean air

Wiesbaden was a well-known spa town in the 1880s, and its leaders didn’t want a coal-burning engine puffing smoke near the hillside gardens where people came to relax. That problem was solved entirely by a water-ballast system, which needed no boiler or combustion. And this might be why the design has aged so well, too. A study of funiculars, published in the academic journal Transport, notes that historic water-powered funiculars made the technology even more energy efficient by using water instead of a motor to move the load. That kind of engineering is a lasting testament to ingenuity. The basic physics is pretty simple: the weight of the descending carriage does most of the lifting, so the only real energy loss is friction in the cable and wheels.

The numbers behind one trip

The railroad is 438.5 meters long and climbs 83 meters along the way. This averages out at about 19 percent, with a maximum gradient of 26 percent at its sharpest point. Each ride lasts about three and a half minutes, and moves at about 4.8 miles per hour. Each carriage can accommodate 50 people going downhill and 40 people going uphill, a difference that reflects standing-room allowances rather than any structural difference between the two carriages, since both cars share the same cable and complete the trip in the same time. The math still has to work out precisely on every trip: the water-filled carriage has to outweigh the carriage full of passengers on the other end, or the system just won't move.

A 19th-century concept that still works today

For more than 130 years, the Nerobergbahn has been using this water-ballast system. ESWE Verkehr's own historical records show that in 1988, marking the railway's 100th anniversary, the state of Hesse officially declared it a protected technical monument. It continues to run every year from April through October, as it always has. For a generation brought up on apps and algorithms, the Nerobergbahn can be a reminder that not all of the smartest engineering ideas require software or sensors. Sometimes all they need is water, gravity, and a good steel cable.