Thursday, July 21, 2011

Time Gaps and Km in the Tour de France

In its live coverage of stage 18 of the Tour de France today, CyclingNews posted the following update:

17:35:28 CEST
Andy Schleck powers under the red kite, with his grimace beginning to curl into a grim. Over 60km off the front for the Luxembourger.
17:35:56 CEST
Schleck has a shade under 3 minutes over Evans, but 3:30 over Contador.
17:36:34 CEST
Pierre Rolland sets the pace for Voeckler. The Frenchman is battling to hold on to his yellow jersey here.
17:36:58 CEST
Voeckler needs to close the gap to 2:35 to hold the yellow jersey.
17:37:24 CEST
Evans and Voeckler lead the yellow jersey group in pursuit of Schleck.
17:38:19 CEST
Schleck appears to have slowed in the final kilometre, his efforts have finally begun to tell in this steep upper section of the climb. He should take yellow by a handful of seconds, but it might be close.

When it was all done, despite being dropped by several of the riders in his group, Voeckler managed to close the gap to 2:21, saving his yellow jersey by 15 seconds.

So what was CyclingNews' mistake? How could they, watching the race on television, so overestimate how much time Andy had on the chasers?

The answer is likely the way time gaps are reported. Andy rides under the kite, the screen says "1.0 km" and next to it a time gap, for example "3:00" (indicated in the report). However obviously at this point the time gap does not apply to 1 km to go: that gap is impossible to determine since the chasers haven't reached that point yet. Instead the time gap is no closer to the finish than the chasers' current position, and with a 3 minute time gap, that's more than 2 km from the finish, not 1 km.

Science of Sport timed the actual gap at 1 km and it was 2:38. So between the point where Andy crossed the 1 km to go kite, when the gap was 3 minutes, and when the chasers crossed the same point the gap had fallen by 22 seconds. The gap was to drop another 21 seconds before Frank Schleck crossed the line in second place, 2:07 back.

So CyclingNews simply underestimated, by close to a factor of two, how much road Voeckler had to reduce Andy's hold on "la meilleur jeune virtuelle".

As an aside, a still air estimate for the power produced by Frank Schleck on the climb of the Galabier was 5.7 W/kg (Science of Sport blog comments). There was reported to be a headwind, but Frank was sitting in the group for most of the climb, protecting his brother's lead. Evans was probably a bit higher than this. But it's all further proof that riders blowing the top off 6 W/kg late in a stage race is, for now, apparently a thing of the past. And just in time for Voeckler, who finally gets to show his real talent. Of course the proof will come tomorrow, when the riders climb L'Alpe d'Huez, sort of the Old La Honda Road of the Tour as far as times are concerned.

No comments: