The M-497 Black Beetle, a US-built jet train, in action. General Electric, Youtube During the 20th century, dramatic visions of what human life would soon be like through technological advances were extremely popular.

People imagined that cheap space travel, permanent colonies on the moon and hovercars would be available for their children and grandchildren.

It didn't quite work out that way, but some of the futuristic technology that actually did get built has since been abandoned.

Specifically, jet trains.

First of all came the French jet train model, the Aerotrain, which was tested in early 1966.

Here's what it looked like in action:

Unlike models in the US and Russia, it wasn't a passenger train, but the designers did later develop one with 80 passenger seats.

The more advanced models looked like this:

Lead engineer Jean Berlin died in 1975 and the French project was abandoned two years later.

Just a few months after the initial Aerotrain test, in July 1966, the US M-497 Black Beetle made its first test run — it was a much larger vehicle.

Two General Electric engines designed for US fighter jets were mounted to the top of an existing railway car by engineer Don Wetzel and tested successfully. Just a few years later Wetzel made a more permanent mark on the modern world as the inventor of the automated teller machine (ATM).

The M-497 still holds the US light-rail land speed record in the United States (183 miles per hour), nearly 50 years after its inception:

Of course, as with any technological development in the mid-late 20th century, if the United States had one, the Russian government wanted one too.

The SVL, or "high speed laboratory car," was constructed in the USSR in 1970.

Like the US model, a passenger train had engines from a Russian jet, the Yakovlev Yak-40, simply attached to the top. The SVL was a little slower than the M-947, reaching 160 miles per hour.

People stopped building jet trains after the 1970s — some countries started going for high-speed rail and some seemed to simply have lost interest, perhaps realising that attaching the engines of an incredibly expensive plane to the top of existing trains was not a viable long-term transport solution.

But all the same, we're glad they tried.