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How a Race Course is Measured

by Karl Gruber
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Anyone who has run a race wearing a GPS to record their stats — including run distance — will swear up, down and backwards that the course was too long. My piece of advice is to not stress over what your GPS says about the length of the race course. 

Most of the time, your thought capabilities have gone out the window during or after the race; I know mine usually do, especially when I try to do simple math late in the race. Wait until you recover and then read this article to understand how exactly a race course is measured and certified.

I will tell you up front that I have never measured a course myself. Even though the process of correctly measuring a race course can get complicated, the concept itself is not that complex. How race car drivers are taught to race is the best analogy I can use to explain how a running race course is measured to certify its distance. Here’s an example:

A number of years ago, I had the opportunity to drive a car on the Mid-Ohio Indy Car race track with one of their driving instructors. With me in the driver’s seat and the instructor in the passenger seat, I hit 115 MPH on the back straight away. At the end of this straight away is a tight hairpin turn, and as you are coming to the end of this long straight stretch of road, you can see that they have put a bright orange traffic cone. This cone is placed right in the apex of the corner, so the driver can see exactly where to turn for the shortest possible distance through the corner in order to have a quick lap time. This is no different than how a running race course is measured AND how you should run a race to have your quickest time possible.

While the USA Track & Field website has a huge, in depth explanation of how this is done, an online article by a guy who calls himself the DC Rainmaker features a somewhat simplified explanation of how he measures a course. Here’s his explanation along with some simple illustrations that say a lot… 

Let’s look at a simple two-turn case. In the below scenario, the actual course distance is officially measured 30cm from the curb. The total course also has a 0.1% error factor (added to it to ensure it’s never short).
 

Taken from page 19 of the USATF measuring manual

Now imagine the typical case where a few thousand (or tens of thousands) of runners are running the course, where will you likely end up?  Probably the red line instead, weaving and swerving around runners.
 

So how much extra does this one measly turn add?  Well… we’ll get there in a second.  The next scenario to look at is the twisting road case.
 

In this scenario, the official course cuts the corners. But in real life?  You’re likely swaying through the full width of the road with a few thousand of your closest friends.

Most runners who race a full or half marathon don’t worry a lot about whether a course is or isn’t measured perfectly, but I have seen many, many runners who become irate that “this course is way too long! My GPS says 27.1 miles!” As you can see above, however, the likeliest scenario is that these runners were weaving off the tangent of the course measurement and actually did run a longer distance than the official measured course. 

So next time your GPS indicates that you ran farther than the announced distance of the race — and before you get in the face of the race director to yell at him or her — kindly consider the above images and explanations first.

As for running your race and cutting all of the tangents, I will tell you that it’s not as easy as it seems. Usually it’s the front runners who have an open road, which is why these seasoned racers know their quickest race time coincides with running the tangents. 

For us mid to back of the pack runners, on the other hand, it’s almost an impossibility to do so. You have so many other runners in the way of the tangent so you do end up running a bit farther than the race course distance. Not only that, when you get so very tired late in a race, you may simply forget that running the tangents of each curve is the best race strategy. 

It’s fun knowing exactly how a race course is measured, but don’t stress over it. Run your race as best as you can and just enjoy the experience!

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