Mass Start or Wave Start

There were 2,750 competitors at Challenge Roth last year before you factor in teams, yet the course rarely felt crowded. It may be forced by the narrow canal swim, but dividing the field into waves of roughly 300 athletes started at 5 minute intervals goes a long way to easing congestion. This may not eliminate drafting, but it certainly makes it easier to manage.

Would we have seen the pictures of packs from Melbourne last weekend had a wave start been adopted for the shortened swim? That’s the question I’m hoping to answer for the IM Talk Podcast next week having been asked by John Newsom to look at the statistics. So what might a wave start have looked like in Melbourne?

Wave Starts: Reducing Congestion on the Ironman Melbourne Course

The answer – potentially – is shown in the graph above. If we are willing to make an assumption it’s actually relatively easy to simulate the impact of wave starts using the result from last week’s race. If we assume that wave starts would not alter an athlete’s splits then I can simulate them by simply adjusting race times recorded at each mat. In this case I’m interested to see what the congestion would be like in T1 if athletes had been started in separate waves.

I tried a number of approaches to the wave start. Firstly I divided by gender, but it soon became obvious that wouldn’t work – at least 75% of the field was male, women were not the cause of congestion. More waves are needed and they need to target age groups, once I made those divisions I started to make inroads into the congestion. It was only when I applied a more intelligent split into five waves that I really made a difference; I ordered age groups by average swim speed and grouped them so that waves were around 400 athletes in size, as small as I could go without dividing the male 40-44 year old division. As the graph shows this does a better job of splitting the competitors at the start of the bike, but did require the benefit of hindsight. More waves with the fastest athletes first is the most effective way to reduce congestion at T1.

Out of interest I also tested how a full length swim might have affected congestion. Had a 3.8K swim been possible, and had the athletes maintained the same pace for the extra distance, we would not see the same problems. It seems the issue may be less pressing when a full length, challenging swim begins the race.

Of course we can never know what would have happened, a switch to wave starts would change the dynamics of the race. There might have been fewer packs, but there would still be drafting. It’s hard to measure the benefits when statistics on drafting are unreliable. Are the gains enough to warrant a change? I can’t say. There are also implications for the competition: I was careful not to divide age groups to ensure head-to-head competition for Kona slots and podium places, but there are Ironman races, like Frankfurt, that do. How much affect does that have? And what about those races that use time trial starts? Texas will be using that method, how does it influence a race? As so often happens one simple question leads to others.

To answer John’s question though, wave starts would have alleviated the congestion at the exit to T1 and this would likely have made drafters easier to catch. But it would also have largely been unnecessary had conditions allowed a full length swim.

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