Have you ever wondered which NZ road races are the fastest?

The first place time or the median time can’t answer this question accurately, because the strength of the field varies from race to race. So I spent the last few months collating data from >100,000 running performances throughout NZ over the last few years to work out which 10km, half marathon and marathon races are the fastest. The analysis works by matching thousands of runners by name/gender/division between races to see how, on average, their performances vary depending on the race they run at. This effectively controls for differences in the strength of field from one race to the next.

For half marathons the fastest in the North island is the Kerikeri half marathon, whereas in the south island the fastest is Southern Lakes half marathon.

The full results are published on a new website for the purpose: http://runningstats.nz

You can click on any race and see how the course speed varied from year to year (presumably for reasons of weather conditions, course changes, course measurement errors, but also other intangibles, such as whether the race was a National or regional champs or not).

The attached figure is a detail from the half marathon comparison page. Bars to the left represent faster races and the difference can be significant (+/-5% for your time).

There is a calculator so you can convert a performance at one race to what would be the equivalent performance at a different race.

Quite a lot of work just to find out which race to do next, but it was a fun little data science exercise.

A ranking of half marathons in New Zealand. Left bars are faster.
A ranking of half marathons in New Zealand. Left bars are faster.