In order for times set in a road race to be eligible for a world record, the course needs to satisfy some rules, two of which are:
- The start and finish points of a course, measured along a theoretical straight line between them, shall not be further apart than 50% of the race distance.
- The overall decrease in elevation between the start and finish shall not exceed 1:1000, i.e. 1 m per km (0.1%).
See rules 31.21.2 and 31.21.3 here. The purpose of these rules are to avoid athletes getting a world record time by being aided by an overall downhill course or having a constant tailwind in a point-to-point course.
In this document there is a list of marathons and half marathons around their world, alongside with an indication as to whether or not they satisfy the downhill/separation rule. I noticed that the Edinburgh Half Marathon is included as compliant with the rule (and therefore a theoretical world record set on this race would be valid). However, if we look at the race information page, specifically the elevation profile, we see that it drops from about 90 m to 10 m, i.e. about an 80 m drop, which is far higher than the 21 m maximum permitted for a half marathon (1/1000 of 21 km).
Plotting the start and finish points on Google Maps, we come to a similar conclusion about the elevation drop.
So my question is: Despite all this, why is the Edinburgh Half Marathon still considered Rule 31.21 compliant?
I also want to note that World Athletics' list has been updated this year and the couse has been unchanged for several years, and is set to remain unchanged for the 2021 edition of the race (this year's edition was cancelled due to COVID-19).
Another surprising fact is that the Edinburgh Marathon – which takes place on the same day and has the same start and finish points – is not even included on World Athletics' list, neither as compliant or non-compliant with the rule. The elevation drop of ~80 m is still too much for a marathon, put proportionally less than the half marathon since the course length it is double the distance.
As a side note, when looking at the route map on the race information page, it may also give the illusion that the half marathon violates the 50% separation rule since the course heads mostly eastwards. However, by using the measure distance tool in Google Maps, we find that the straight line distance is about 9 km – so it is safe by about 1.5 km.
Up until now, the times set in the Edinburgh Marathon and Half Marathon do not come close to the world records and it seems very unlikely that a world record will be attempted in Edinburgh in the near future. However, the course being world record eligible can influence non-professional runners who are considering running it as a PB attempt, since it means that whatever time they achieve is "valid" as a PB (compared to, say, a race going from the top of a 2000 m mountain pass to sea level, which would be considered "cheating" since the massive elevation drop will probably make everyone several minutes faster).