Railway gauges

General 4 Comments

Episode 3 in a series “Things that are the way they are because of constraints that no longer apply” (or: why we don’t change processes we have invested in that don’t make sense any more)

The standard railway gauge (that is, the distance between train rails) for over half of the world’s railways (including the USA and UK)  is 4′ 8.5″, or 1.435m. While a few other railway gauges are in common use, including, to my surprise, in Ireland, where the gauge is 5′ 3″, or 1.6m. If you’re like me, you’ve wondered where these strange numbers came from.

Your first guess might be that, similar to the QWERTY keyboard, it comes from the inventor of the first train, or the first successful commercial railway, and that there was simply no good reason to change it once the investment had been made in thbat first venture, in the interests of interoperability. There is some truth to this, as railways were first used in coal mines to extract coal by horse-drawn carriages, and in the English coal mines of the North East, the “standard” gauge of 4′ 8″ was used. When George Stephenson started his seminal work on the development of the first commercial railway and the invention of the Stephenson Rocket steam locomotive, his experience from the English coal mines led him to adopt this gauge of 4′ 8″. To allow for some wiggle room so that the train and carriages could more easily go around bends, he increased the gauge to 4′ 8.5″.

But why was the standard gauge for horse-drawn carriages 4′ 8″? The first horse-drawn trams used the same gauge, and all of their tools were calibrated for that width. That’s because most wagons, built with the same tools, had that gauge at the time. But where did it come from in the first place? One popular theory, which I like even if Snopes says it’s probably false, is that the gauge was the standard width of horse-drawn carriages all the way back to Roman times. The 4′ 8.5″ gauge roughly matches the width required to comfortably accommodate a horse pulling a carriage, and has persisted well beyond the end of that constraint.



QWERTY keyboards

General 2 Comments

Episode 2 in a series “Things that are the way they are because of constraints that no longer apply” (or: why we don’t change processes we have invested in that don’t make sense any more)

American or English computer users are familiar with the QWERTY keyboard layout – which takes its name from the layout of letters on the first row of the traditional us and en_gb keyboard layouts. There are other common layouts in other countries, mostly tweaks to this format like AZERTY (in France) or QWERTZ (in Germany). There are also non-QWERTY related keyboard layouts like Dvorak, designed to allow increased typing speed, but which have never really gained widespread adoption. But where does the QWERTY layout come from?

The layout was first introduced with the Remington no. 1 typewriter (AKA the Scholes and Glidden typewriter) in 1874. The typewriter had a set of typebars which would strike the page with a single character, and these were arranged around a circular “basket”. The page was then moved laterally by one letter-width, ready for the next keystrike. The first attempt laid out the keys in alphabetical order, in two rows, like a piano keyboard. Unfortunately, this mechanical system had some issues – if two typebars situated close together were struck in rapid succession, they would occasionally jam the mechanism. To avoid this issue, common bigrams were distributed around the circle, to minimise the risk of jams.

The keyboard layout was directly related to the layout of typebars around the basket, since the keyboard was purely mechanical – pushing a key activated a lever system to swing out the correct typebar. As a result, the keyboard layout the company settled on, after much trial and error, had the familiar QWERTY layout we use today. At this point, too much is invested in everything from touch-type lessons and sunk costs of the population who have already learned to type for any other keyboard format to become viable, even though the original constraint which led to this format obviously no longer applies.

Edit: A commenter pointed me to an article on The Atlantic called “The Lies You’ve Been Told About the QWERTY Keyboard” which suggests an alternate theory. The layout changed to better serve the earliest users of the new typewriter, morse code transcribing telegraph operators. A fascinating lesson in listening to your early users, for sure, but also perhaps a warning on imposing early-user requirements on later adopters?