With close to a century of history behind it, slot car racing is still a very active hobby because it is becoming the closest kin to auto racing around the world. The first slot cars were made by Lionel (USA) and appeared in their catalogues from 1912.
I first introduced my son to slots about 25 years ago with an HO scale set that offered a lot of realism even in that small a scale. We chose the Aurora Plastics Corp. HO vibrator sets that were so popular in the USA.
The tiny cars fascinated the public, and their cost and space requirements were better suited to the average consumer than the larger scales.
Most of today's "In The Groove" racers are larger.
1/24 - The choice scale for commercial racing centers. This scale is only used widely in the United States and Australia. Everywhere else when slot racing is discussed, it is mostly about the smaller 1/32 scale or H.O. cars, according to John Ford, a leading authority on slot car racing since 1965.
Ford noted that 1/32 is the scale of choice for most of Europe. Mostly because of the high cost of housing a slot car track, the Europeans have adopted the smaller cars because the tracks are much smaller, and a racing center could easily be put up in someone's home. This is also the case for most club tracks World wide.
HO scale is 1/64, a little larger that the original HO scale of 1/87.
The current breed of slot car racers offer a lot more speed and agility with some models developed as drifters capable of four-wheel slides.
In 2004, the digital control systems which had revolutionized model railroading began to appear in 1:32 slot cars, offering the promise of multiple cars per lane and more realistic passing. Some speculate that digital control will soon replace conventional slot racing, but only time will tell if the appeal of racing on parallel slots with simple controls, which has endured for half a century, may yet outlive the expectations of the high-tech advocates.