Monorail

Every other railway on this map balances a train across two rails set a fixed gauge apart. A monorail throws that away and runs the whole vehicle along a single beam that is narrower than the car itself — so the train doesn't sit between its supports, it wraps around them or dangles from them. It looks like the future, and has since the 1950s. It has mostly stayed a curiosity anyway.

How it works

The defining rule is simple: the guideway is narrower than the vehicle. A slim concrete or steel beam runs the length of the route, usually elevated on thin columns, and the train grips it rather than resting across a pair of rails. Because the beam is skinny and raised, a monorail casts a small shadow and needs a narrow footprint — part of why it reads as clean and space-age. Almost all modern monorails run on rubber tyres rather than steel wheels, which is where several of their real advantages come from.

Two families: straddle and suspended

There are two ways to attach a car to one beam, and they split the whole category in half.

• Straddle-beam — the car sits on top of the beam like a saddle, with rubber load tyres rolling along the top and guide tyres pressing the sides to keep it centred. This is the ALWEG design from the 1950s, and it dominates today: Disney's park monorails, the Tokyo Haneda airport line, and Chongqing's large urban network are all straddle-beam.
• Suspended — the car hangs beneath the beam, swinging slightly on curves. The oldest and most famous example is Wuppertal's Schwebebahn in Germany, carrying passengers over a river since 1901; Japan's Chiba Urban Monorail is a large modern one.

Why it stays niche

For all the futuristic imagery, the monorail rarely wins when a city sits down and does the maths, and the reasons are structural rather than aesthetic.

On top of that, switching is hard: you can't just throw a set of points on a solid beam, so junctions need heavy moving-beam mechanisms that are slow and expensive. Capacity also tops out below a full metro — respectable for a feeder, but not trunk-line throughput. Add the bespoke everything, and a monorail often costs like grade-separated heavy rail while carrying less.

Where it earns its keep

The rubber tyres are the upside. They make monorails quiet, and they grip well enough to climb steeper grades and tighter curves than steel-on-steel rail — useful on hilly, cramped alignments. Combined with the narrow elevated beam, that makes monorails a good fit for airports and theme parks, where a short self-contained loop with no rail connections is exactly the point, and for a handful of full city lines — Chongqing being the standout — where terrain and space favour a slim viaduct. Genuinely useful in its niche; just rarely the right answer for a city's main line.