Thursday, November 22, 2012

Kennedy Trail dirt: Mixing things up for Low-Key Hillclimbs

A big motivation for Kennedy was that it would mix things up a bit: not only the experience, but also the scoring. While the results in typical climbs can get almost frustratingly predictable, on the dirt skill, confidence, and balance can play a substantial role.

I like to compare the scores for riders who did climbs in any given pair of weeks, to see how their scores different (RMS average difference). Here's the result:

w1: Montebello
w2: Quimby Road (Murillo start)
w3: Morgan Territory Road (S)
w4: Hwy 9 from Boulder Creek
w5: Hwy 84 - West Alpine
w6: Soda Springs
w7: Kennedy Trail

rms score delta (riders doing each)
       w1    w2    w3    w4    w5    w6    w7
w1      .  4.73  2.99  5.29  6.04  3.40  6.88   w1 
w2   4.73     .  4.96  7.91  5.77  3.33  6.48   w2 
w3   2.99  4.96     .  4.07  6.41  3.09  6.72   w3 
w4   5.29  7.91  4.07     .  5.66  5.59  7.46   w4 
w5   6.04  5.77  6.41  5.66     .  4.59  8.02   w5 
w6   3.40  3.33  3.09  5.59  4.59     .  6.70   w6 
w7   6.88  6.48  6.72  7.46  8.02  6.70     .   w7 
       w1    w2    w3    w4    w5    w6    w7

The week-pairs for which scores were the closest match were Montebello and Morgan Territory. A close second was Morgan Territory and Soda Springs. The biggest difference was between Kennedy Fire Trail and W Hwy 84 - W Alpine, while Kennedy Fire Trail vs West Highway 9 was also a large difference. Scores between Kennedy and any other week differed RMS by at least 6.48 points. There's other weeks which also had mismatch, for example Quimby versus W Hwy 9, but in general Kennedy proved the most unique.

Here's a plot of the W 84 scores versus Kennedy scores for riders who did both. The scoring algorithm clumped the scores around the line y = x, so there's no evident strong bias to faster or more endurance-oriented riders. The only bias is towards riders relatively better or worse at climbing on dirt, as it should be:

week 5 vs 7

So the scoring worked well. As I've described before I calculate a parameter I call the "slope factor" which corrects for riders being relatively closely or relatively widely spaced in time on a given climb. Steeper hills tend to spread riders out more than flatter rides. But dirt also spreads people out more than pavement. It is curious to see if the result matches this expectation. Here's the scoring factor plotted, where each point relating road grade to slope factor is indicated with the week's number:

slope factors

Kennedy, indicated with the brown 7, is indeed an outlier, and separated the riders more than any other climb. This year's scoring code helps limit the relative influence of Kennedy versus, for example, Mount Hamilton on Thursday which traditionally yields far less separation due to its modest grades and intermediate descents.

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