It's easy to take our daily modes of transport for granted; the modern airplane had its humble beginnings in incredibly risky flights made by the Wright brothers, rail transport evolved from mine carts and funiculars, the first bicycle didn't have a pedal — the list goes on.
Almost every widely used form of transportation was once a crazy idea before it became the mass form of transit we're accustomed to today.
Of course, along the way, there have been many ideas that didn't quite make the cut. Here are a few ideas that never quite gained the mass appeal their inventors were hoping for.
1. The Monowheel
Almost as soon as the first pedal-powered bicycle was invented in the 1860s, inventors set out to do away with that cumbersome second wheel.
Quite hilariously, one of the reasons this transportation technology never really took off is because of its propensity for something the inventors called "gerbilling." If a monowheel rider hit the brakes or accelerated too quickly, they were likely to spin inside the machine like a pet gerbil in its wheel.
That didn't stop inventors like J. A. Purves creating monowheel variations like the Dynasphere spherical car. The vehicles often employed gyroscopic steering mechanisms to help with balance.
2. The Iron Dobbin mechanical horse
Not much is known about the origin of the Iron Dobbin, other than the fact that it was developed by an Italian inventor. The design appeared in a 1933 issue of Popular Science, in which it was described as "the mechanical horse that trots and gallops on steel piped legs, under the impulse of a gasoline engine."
The Italian military of the time considered using the walking transportation machine to train the children of the Gioventù Italiana Littorio (Italian Fascist Youth Movement) to ride. Ultimately, however, the military decided that the vehicle was impractical.
3. The Railplane
The Railplane was essentially a monorail powered by propellers. Most planes in the 1930s used propeller engines, so inventor George Bennie thought he'd make a hybrid train with the benefit of a plane's engine.
The idea was to build the Railplane's tracks above that of locomotive trains so they could make the same trips in a quicker time.
Sadly, Bennie, who financed the project in its beginnings, was never able to find the financial backing needed to build the first proposed transportation line from Edinburgh to Glasgow, and by 1937 the inventor was bankrupt.
4. Moving sidewalks
Almost a century before moving walkways started to be commonly used in airports and other public transport centers; the moving sidewalk was devised as a way of moving the masses in city centers.
Invented by engineer Max Schmidt, the sidewalk consisted of three concentric rings. The first was stationary, while the second moved at 4 km/h, and the third at 8 km/h, allowing walkers to adjust to the slower transportation speed before moving onto the faster one.
It was first unveiled at Chicago World’s Fair in 1890 and later proved to be a huge success at an exposition in Paris (pictured above). Some believe it was never implemented due to pressure from other transportation providers of the time.
5. The Transit Elevated Bus (TEB)
It seems like it was so recently that China's traffic-straddling bus was touted as a disruptive transportation technology that would end traditional bus services. The idea seemed weirdly brilliant: to have a bus-like tram that would never have to stop in traffic because it could simply glide above all cars.
Unfortunately, the TEB prototype now sits rusting in a junkyard, and 32 people connected with it have been arrested due to illegal fundraising. As The Guardian reports, though it looks impressive, the public transportation vehicle was never as roadworthy as its creators wanted people to believe.
6. Flying cars
Some, including companies that have invested great amounts of money, still argue that the flying car will one day take off as a means of personal transportation — despite the fact that you'd need runways all over cities to make them possible.
Famous astrophysicist Neil deGrasse Tyson argues that flying cars will never happen because they would be immensely dangerous to the public and would cause too much noise pollution in urban centers. Though some examples, like the Terrafugia (video above), might be promising, it only reaches a maximum flying speed of 115 m/h.
7. The nuclear-powered car
Perhaps the best-known example of a nuclear-powered car is the Ford Nucleon. It is a stunning example of a retro-futuristic transportation technology that never gained widespread usage.
The idea for a car with a reactor at the back was suggested by Ford in 1958. As can be seen in the picture above, the cab of the car was placed farther forward than in normal cars so as to protect the driver and passengers from radioactivity.
Though the Nucleon could supposedly travel up to 5,000 miles (8,046 km) before it needed to be recharged, this car never became a thing for extremely obvious reasons.
8. Space elevators
The space elevator was devised over a century ago. The machine would see a cable anchored to Earth stretching 35,000 kilometers beyond geostationary orbit. Gravity and centrifugal force would keep it taut and lasers on the ground would beam power to “climbers” that would crawl up the cable with their load.
A maglev Startram train concept (pictured below) that could launch rockets into space, without the need for huge amounts of fuel, has also been proposed.
Unfortunately, some pretty massive hurdles would need to be overcome to make this form of space transportation possible. Incredibly strong materials, that might not exist, would be needed to withstand the strain on the tether, while incredibly precise thrusters would likely be needed to stop the elevator crashing into satellites or space junk.
9. The gyro monorail
The first public demonstration of the gyro monorail was given by inventor Louis Brennan on November 10, 1909, on grounds of his house in Gillingham, Kent, UK.
The vehicle was designed so as to maintain balance via two vertical gyroscopes mounted side-by-side and spinning in opposite directions. This allowed it to overcome the instability of traveling on a single rail. The monorail could also bank on turns, somewhat like an aircraft, allowing it to make sharper turns than typical trains of the time.
Though Winston Churchill is reported to have ridden in one of the two prototypes made by Brennan and is said to have been a fan, the transportation project never went beyond the prototype phase.
10. The jet-powered train
During the Cold War, the Soviet Union and the United States both experimented with the idea of a turbojet train that had a pair of jet engines on an aerodynamic redesigned front car. Estimates at the time said the transportation technology could reach speeds of 250 to 350 km/h.
Ultimately, it was decided that the jet engines consumed too much fuel to be widely used. The safety of the train design was also put into question, as one minor issue on the rail line would have had the potential to cause a catastrophic derailment.
11. The three-wheeled car
In principle, the three-wheeled car is such a terrible form of transportation that it's best known as a running joke in British comedy classic Mr. Bean.
And yet, it's making a comeback of sorts. Why? Because urban mobility trends mean that more people want smaller cars to drive around crowded city centers. Still, we'll never be able to get rid of the image of the Reliant Robin (pictured above) rolling over after making too sharp a turn.
In the history of transportation, there will inevitably be ideas along the way that are either left behind or revisited. They do say trends eventually come around full circle, so who knows, one day we might yet see monowheels on our roads, or moving sidewalks that can transport hundreds of people at a time.