When asked how long an athletic track is, everyone answers with some confidence: 400 meters! Which is true, although every correct answer should begin with “It depends.”
I joke, but not entirely
First of all: the length of athletic tracks is standard and was decided by World Athletics (formerly Iaaf) in, precisely, 400 meters. The distance is not random but derived from the so-called “quarter mile,” which is a quarter of the English mile, or just over 400 meters, then rounded down to 400.
However, noting that the tracks are composed of several loops or lanes and knowing a bit about geometry, the question arises: is the loop/lane number 1 (which is always the innermost one) shorter than the outermost one. True, and it is no coincidence that for races involving distances greater than 100 meters, athletes do not start at the same starting line, but at different distances from each other so that they are at the same distance from the finish line.
To be precise, to be 400 meters long is only the innermost lane, while proceeding outward and considering a track with 9 lanes, this will be more than 460 meters long, that is 60 meters longer! What never varies, however, is the length of the two straights, which are always 84.39 meters.
At this point you might ask how it is possible for the 100-meter flat track to be contested on these tracks if … there is no straight of at least 100 meters. As you can see, however, the tracks are not oblong donuts, or rather they are, but they also have an appendage that lengthens the straight, allowing for precisely the fateful 100-meter distance.
The geometry is not that stable
Well, do you understand what track design rules are established by World Athletics? Then we can proceed to question them: there are also athletic tracks that have longer straights, some up to 97.26 meters, which is almost 100 and still almost 13 meters longer than the ones we were talking about earlier.
How is that? The reason is quickly stated: not all athletic tracks are included in sports facilities exclusively dedicated to them. They often have to share space with soccer fields or other sports played outdoors. In order to, literally, run around these rectangles with proportions that do not reconcile with the geometry of athletics, the tracks adapt and, for example, lengthen their straights and compose the curved parts no longer in a curve with a single radius but also with polycentric curves or composed of two sectors of a circle joined by a small straight.
This is also why many athletes who train on dedicated tracks (that do not rise around fields of other sports) find themselves displaced when they run in hybrid facilities: the straight they are used to is in fact no more 84.39 meters but much longer.