Saturday, July 30, 2011

Strava urban KOM matching

On July 12 I rode up Kansas Street on Potrero Hill in San Francisco, as someone else asked me to generate data for a segment there since my HTC Incredible phone has relatively good accuracy here. So I did that, and after defining the segment, I had the KOM. Not too surprising, since typically if any other Strava users had made a hard effort between the same two end-points they probably would have created the segment earlier. Here's that ride. As you can see, I was lucky to have beaten out Steve Smith's effort from May. He'd done a San Francisco climb-fest and had done Kansas only one second slower.

The issue on that ride was in addition to the Kansas climb Strava also gave me credit for Rhode Island, one block over. I had two KOMs, one block apart, from the same ride.

So yesterday since I ended up at the 4th and King Caltrain with my small backpack and no laptop, I decided to try and validate my Rhode Island "KOM". I wasn't quite sure where the end-points were (the embedded maps don't render on my phone), but I got up to speed where the climb started mid-way between 17th and 18th. This was my first mistake: the climb was defined to start right at the corner of 17th. Then at the intersection of 18th I stopped to wave a waiting car past. This cost me a bit more time. But the rest of the way was smooth going. I went all the way to Southern Heights, beyond which Rhode Island steeply descends.

I felt it was a good effort, and had a good chance of taking some time off that faux-KOM I'd set earlier. So when I got home I uploaded the data from my phone, went to the laptop, and checked the result.



I was 3 seconds short. But what I had done is "broken" my standing KOM up Kansas, and in fact set a KOM on De Haro, one block in the other direction. So instead of one bogus KOM, on Rhode Island, and a legitimate KOM on Kansas I now had three bogus KOM's: Kansas, Rhode Island, and De Haro.

Strava obviously needs to tighten its segment matching criteria, especially for urban segments where streets are densely located. Some areas, like the top of Old La Honda Road, have signal reflection problems where relatively large errors can result. But you can't set the matching threshold everywhere based on these worst-case locations.

Anyway, now I need to go do a hard ride up De Haro, as well. Fortunately Wisconsin, one block further, doesn't go through so I know there isn't a segment there I can contaminate.

Of course, the only reason I have KOM's on these climbs, valid or otherwise, is they're sufficiently obscure that none of the significant number of faster riders around here have bothered. But that's part of the beauty of Strava: it taps into the animal instinct to mark territory. There's more territory than the top dog can pee on, leaving space for even lesser dogs like me.

appendix: after posting this I went out and rode hard up De Haro. This fixed my bogus De Haro KOM, but also registered a new KOM up Rhode Island. So I think for these segments to be distinctly meaningful Strava simply needs to fix its matching algorithm.

Thursday, July 28, 2011

VAMs on L'Alpe d'Huez in 2011 Tour de France

This year the Tour de France climbed L'Alpe d'Huez, the "Old La Honda" of the Tour.

The "official" climbs is 13.8 km long according to Wikipedia, and gains 1099 meters according to Strava, an average grade of 7.96% (the GPS recorded distance depends on trajectory through the switchbacks, for example, and in any case GPS isn't that accurate on distance along curvy routes). It was climbed during the Tour de France stage 19 this year.

The climb was complicated by riders arriving at the start in small groups. Timing thus needed to consider the finishing time, well documented by the race, but also the starting time. According to Wikipedia:

Since 1999 photo-finish has been used from 14 km. Other times have been taken 13.8 km from the summit, which is the start of the climb. Others have been taken from the junction 700m from the start.

The following times were posted as "official" by the Inner Ring on Twitter:

official times

I assume these are from the camera Wikipedia says is 14 km from the finish.

The Science of Sports Blog claims the following:
In terms of the historical context of the 2011 performances, the overall time for Contador was 41:30. Sammy Sanchez was the fastest of the day in 41:21, while Pierre Rolland, first to summit, did it in 41:52 because he started the climb with a 51 second lead (bear in mind small errors in timing off the TV).

He initiated timing at "the start banner of the climb".

The "official" times had Sanchez 41'45", Contador 41'54", and Rolland 42'22". These times lag Science of Sports' by 24", 24", and 30". If as I assume the difference is due to a 200 meter difference in start location than this corresponds to Contador and Rolland riding at 30 kph and Rolland at 24 kph, to crude precision.

So to convert the "official" times to the times for 13.8 km "chrono", I assume all riders other than Rolland rode the 200 meters at the same rate as Contador and Sanchez, taking 24 seconds. Perhaps this is optimistic for the 200 meters in many cases, but that makes it somewhat pessimistic for the time over the climb itself. However, assigning pack times to individuals, as is done here for both the start and finish of the climb, adds several seconds of error, so I would put all times here with ±5 second error bars.

So here's the results: I show rider, time, and VAM. I also calculated an estimated W/kg, but as I've described before, there's plenty of potential errors in such estimates, especially when riders draft each other. Jonathan Vaughters tweeted 5.4 W/kg for Tom Danielson, very close to my still air estimate of 5.51 W/kg, but then I read a claim this was revised to 5.7 W/kg, so take all that for what it's worth. My calculation has Sanchez at 5.67 W/kg, with numerous assumptions.
rider                  min   VAM
Samuel_Sanchez         41.35 1594.7
Alberto_Contador       41.50 1588.9
Pierre_Rolland         41.87 1575.0
Cadel_Evans            42.07 1567.5
Damiano_Cunego         42.07 1567.5
Andy_Schleck           42.07 1567.5
Frank_Schleck          42.07 1567.5
Peter_Velits           42.07 1567.5
Thomas_de_Gendt        42.07 1567.5
Tom_Danielson          42.37 1556.4
Jean-Christophe_Peraud 42.57 1549.1
Hubert_Dupont          43.22 1525.8
Rein_Taaramae          43.22 1525.8
Ryder_Hesjedal         43.22 1525.8
Ivan_Basso             43.22 1525.8
Levi_Leipheimer        43.22 1525.8
Jerome_Coppel          43.63 1511.2
Kevin_De_Weert         43.88 1502.6
Rob_Ruijgh             44.18 1492.4
Thomas_Voeckler        44.48 1482.4
Christian_Vandevelde   44.48 1482.4
Yury_Trofimov          44.48 1482.4
Arnold_Jeannesson      44.50 1481.8
Robert_Gesink          44.63 1477.4
Carlos_Barredo         44.68 1475.7
Blel_Kadri             44.90 1468.6
Remy_Di_Gregorio       45.55 1447.6
J_Blazquez_Hernandez   45.98 1434.0
Haimar_Zubeldia        46.12 1429.9
Richie_Port            46.38 1421.6
Chirs_Anker_Sorensen   46.38 1421.6
Sebastien_Minard       46.43 1420.1
Bauke_Mollema          46.43 1420.1
Christian_Knees        46.43 1420.1
Niki_Terpstra          46.72 1411.5
David_Loosli           46.80 1409.0
Egoi_Martinez          46.93 1405.0
Sandy_Cesar            46.93 1405.0
Gianni_Meersman        46.93 1405.0
Jakob_Fugelsang        46.93 1405.0
Jonathan_Hivert        47.90 1376.6
Jeremy_Roy             47.95 1375.2
If you told me a few years ago you could win the Tour with a 1570 VAM up L'Alpe d'Huez I'd have laughed at you. Sure, maybe in the Lemond-Indurain era, but not since the age of Armstrong, who revolutionized pro cycling by previewing climbs, training in the rain, and drinking Michelob Lite.

Quick plot of these results:
VAMs


For perspective, the Strava KOM is 48.75 minutes, a VAM of 1353. Even in this kindler and gentler era, the pros humble us poor weekend warriors even after having climbed the brutal Telegraph and Galabier in week 3 of a grand tour. But this is expected: it's what they do, they're probing the limits of human ability. And maybe, just maybe, they're no longer exceeding them.

Tuesday, July 26, 2011

Coastal Trail Runs: Golden Gate 30 km

My first 30 km trail running race of the year was yesterday: the Coastal Trail Runs Golden Gate.

The Marin Headlands provided for a gorgeous course, with four big climbs and one little climb at the end, along with miscellaneous rollers liberally sprinkled between the major bumps.

On Tue I had gotten stung by a bee while riding to work through Palo Alto. My face swelled up within an hour, but I got it under control with ice. When I awoke on Wed, however, the swelling was back in force, and Wed and Thu the allergic reaction left me fatigued. I felt a bit better on Friday, still a bit tired but not 100%. My lip was still puffy when I awoke early on Saturday, but otherwise I felt much better. I'd not run at all in a week and a half, but at least I'd gotten in some decent cycling through that Tuesday commute.

In April I'd done 26 km and 27 km training runs on many of the same trails used in the race, then on July 5 I did a strong 29 km run there. With the improved hydration and calorie intake available on a supported race, I felt I would be able to put in a good effort. The goal was to run every one of the climbs at tempo, and come into the finish fast but tired.

start
Starting (Cara Coburn)

So after overenthusiastically jumping the "gun" by a half-second (whoops!) I was second into the start of the first climb, following a guy in a red sleevless shirt who was just flying. He disappeared out of sight and I settled into run-walking my own pace up the hill. I was then passed by a woman who I tried to follow for awhile, but finally let go as she was going too quickly for what I thought I could hold for 30 km. I decided then to not worry too much about who was around me but run my own pace.

first climb
First climb (Cara Coburn)

One constant goal is to improve my speed on downhills. Sometimes on trails there's a forbidden speed gap: you can descend at a speed which allows for stopping or go fast enough it's more of a controlled fall. In between is the forbidden zone where you're braking to limit your speed, and that braking exceeds the available traction. I have a hard time crossing this gap: I like having the out available of being able to stop if necessary. The good runners seem to be unafraid of falling occasionally, and are willing to take that risk of committing to running past the speed gap. Once that commitment is made the only way to slow gracefully is to reach the end of the steep grade. So for short downhills, those where I know I won't get into trouble, I try to let gravity take me a bit further than I'm comfortable.

I seemed to be doing okay with this, not getting passed on the downhills. I reached the first checkpoint at Tennessee Valley stables in good position. The runners ahead, none of whom had water, blew through this stop. I had a bottle in my Nathan belt, which I was drinking while I ran, but stopped long enough to drink two cups of Hammer carbohydrate solution, which Coastal mixes nicely dilute. Even though it was foggy and cool I wanted to stay on top of my hydration. I then fumbled grabbing three Clif Blok carbohydrate chews, eating one and storing the remaining two in my belt pouch.

All of this allowed the runners I'd been chasing to increase their gap, but I was no longer worried about them. However, I worried a bit more when soon after the stop, on the flat Tennessee Valley trail, a group of around six guys ran past me as if they were doing a 10k. I slotted in with them, wanting to take advantage of the draft, figuring if I'd been faster on the first climb I'd be faster on the next.

Soon enough we turned onto the Fox Trail. I'd not been here before: it falls between the Coastal Trail which goes by Pirates Cove to the west and, to the east, the Miwok trail. Coastal-Miwok provides a fantastic loop, so I'd never felt compelled to take the relatively broad Fox trail. I'd asked about it at the start, however, and had been told it got steep toward the end. So as the climb began I settled into a sustainable pace, even as others in the group surged ahead, saving something for when it steepened.

And sure enough as the climb progressed the runners towards the front slowed, and I regained ground on then. As we reached the top of the climb where Fox merged with the Coastal Fire Road, I was with a group of two with two more further up the trail. We then began the descent towards the turnoff to the single-track Coastal Trail, the highlight of the course.

I was pleased I was able to descend with these two guys over some of the steeper sections of the fire road. With the coastal fog, we didn't see anything of the water to the left, but the valley to the right was clear enough well below our height. Eventually I saw some ribbons to the left with a sign: what did that say? But the runners I was following kept going, so I figured it was just a minor trail I hadn't noticed before. In retrospect, I can barely believe I'm writing this: I've been on these trails many times. But I have such an inferiority complex about my navigational abilities that I always assume without question that others who appear more confident are correct. So I followed the other two.

The descent got steeper and less familiar. Muir Beach was getting awfully close ahead, the view clearing as we descended. We'd missed the turn.

"This is the wrong way", I said.... "when's the last time you saw a ribbon?"

"Back there", one of the two responded, "but this is the right way: we're following those guys up ahead."

Lemming line... It's tempting when you commit to a course of action to stick to it, long after it becomes obvious it was a mistake. So even at this point I took a few more strides, a few more precious meters of altitude squandered, before stopping. I stopped.

A runner was approaching from behind. Despite overwhelming evidence, I still needed to check. "The Pirates Cove trail is back up the hill, right?" I asked. She confirmed.

So back up the hill I went. All of the early pushing of my pace was now flushed down the proverbial toilet. Those tenths of a second saved following optimal trajectories through corners were tossed away as I'd just given away ten minutes or more in a massive exhibition of neural flatulence.

As I ran, I was amused to see more runners with numbers pinned on their shirts or shorts descending. "Wrong way!" I shouted as I climbed. Yet once again in my surrealistic haze I started to doubt if I was making a mistake. It was as if my existing trail knowledge was all a strange dream.


Anton near Pirates Cove in 2010

But there it was ahead: the turn-off to Pirates Cove, marked with a striped ribbon. The marking wasn't super obvious: a single ribbon on what is a tricky corner. Maybe Wendell could have invested a few more here. But navigation is part of the trail running game, after all.

Even though I saw a runner in the distance, one who had obviously been behind me earlier, I decided to not let this snafu take me down. This, after all, is a trail unmatched in its beauty: a dream-like run along the rugged Pacific Coast. I'd specifically trained here to improve my speed on the undulating, twisting route, and it had worked. I felt like I had this thing nailed, and made great progress even up the steep trail which extends above the strength-sapping stairs which rise above the Cove. That section had kicked my butt more than once.

The trail gave way to fire road, and I ran at a good pace on the steep descent to Tennessee Valley.

The Tennessee Valley trail is a relative low point in several ways on this run. It's low in altitude, but being flat and broad with a very gradual uphill slope, it is slow going without much scenery for distraction, and there's enough cyclists and hikers to require dodging. Here the two guys I'd followed off the course repassed me. They complemented me on my speed on the single track, but here they were clearly that little bit faster.

Then the rest stop... a volunteer filled my bottle. The weight weenie in me tends to over-analyze these moment. I knew I didn't need the full bottle to reach the next rest stop, but then if filling it would allow me to skip refilling it later, perhaps that compensate for the increased time taken to carry the bottle up the Marincello trail. In retrospect I probably should have also factored in the increased fatigue from carrying it up the Marincello trail, and stopped half-way... But either way I wanted to err on the side of too much water. The plan was to down a quick cup of Coke, and two of water, at the stop, but not spend any time refilling.

We merged here with runners doing other courses: the half-marathon and the full marathon (on their first of two laps). They'd started a bit later but since we had run the Pirates Cove loop runners here with me were slower. This was nice, as passing people on the climb gave me the opportunity to share greetings with other runners, and, I have to admit, helped my confidence. From my own race I don't think I was passing anyone. This wasn't a great sign, I decided, but I still felt I was running well.

At the summit we merged with Bobcat trail. I ran a briefly with a 50 km runner (sharing the same course to this point). He said he could run our pace all day. I told him I was getting tired... I wasn't slow at this point, but I was getting a bit worried with there still plenty of running left to go.

Alta Trail, which follows Bobcat, is up-and-down single track along the ridge separating the Headlands from Sausalito and Highway 101. Normally this is stunning, but here the wind-blown fog condensed into actual rain, and the trail in spots was even muddy. If I were hiking I would have frozen wearing only my tights and my event "technical" T-shirt, but under these circumstances I was fine.

For part of this way I found myself running next to the woman who'd passed me on that first climb. I wondered how she'd gotten behind me, especially given my wrong turn (try not to think about that, I told myself!) Again she slipped past me. I also ran with some people who seemed to be on the marathon/half marathon course. I should have been passing them, but was content running at their speed. I was becoming increasingly invested in my plan to drink a Coke at the final stop. I was banking on that caffeine + corn syrup boost.

The aid station approached. I checked my bottle: 1/3 left, which should be enough, so returned it to my belt and shouted "Coke!" as I reached the table. "We don't have any Coke" the happy volunteer responded.

My world froze.

No Coke? But I always drink Coke at the last stop. Invariability it gives me a much-needed kick to crank up the pace over the final kilometers. I considered abandoning right there. But instead, I went for two water cups and a quick Clif Blok. I declined a third water cup, thanked the volunteers, and began my descent.

Flash back to last year. This descent nearly took me down. My legs were in pain the whole way as I hobbled down the long, gradual way. Steeper and I would have been forced to take short steps and it would have been fine. Flat and the impact is less so I would have been fine. But gradual descents are the worst.

This year was better, but not by much. First my left leg, then my right let me know they'd rather be supine, thank you. But of course I continued on, trying my best to distribute the load to the less sore bits. My shoes, which normally feel cushy, felt ridiculously thin.

I reached the turn-off to the Coastal Trail climb to Conzelman. This has been burned into my memory from having missed it during a race last year. I saw runners ahead of me make the turn. I followed.

The climb, albeit short, was a relief. I knew I was going slower than I had any climb to this point, but I was still "running", and that was good. I feared the top, however: Conzelman Road would mark the return of gradual descending, and far worse than the Coastal Trail descent, on asphalt instead of hard dirt.

Before descending Conzelman climbed gradually as it passed the military installations along the coast. This alone was painful, and I knew the descent would be worse. I managed to trot onward, trying to ignore the growing pain in my legs.

Over the top, and I was relieved to see the pavement disappear. Road construction here was unfinished, and instead of pavement I had soft dirt to cushion my footfalls. Trotting continued, and the discomfort was bearable.

Field Road arrived and with it a return to pavement. Here's where I cracked. Once entering the pavement, my trot turned into more of a shuffle, but when the pain in my legs was joined by a sharp stitch on my right side, I stopped and bent over, defeated. I started to walk, slowly, focusing on my breathing.

"Are you okay?" a woman asked as she passed, "I can get help!"

"Not really, but if I walk, I'll make it to the finish. The finish is close," I responded, fully engrossed in my own misery.

"I'll wait for you at the finish!" she replied, and continued.

I walked a few seconds more, then as the grade leveled, decided to try running a bit. And that worked: slowly, barely running, but clearly better than walking.

We briefly entered the Rodeo Lagoon trail before turning off to the right to descend the staircase to Bunker Road.

Ouch... this hurt, as I took the steps slowly, one at a time. Then I heard behind me two women talking: "It's funny how my left leg feels unstable". I laughed and shouted back to them: "you, too?" That was exactly how I felt as I took each step, one by one.

I reached the road and this was the final stretch to the finish. No sprint for me, but I was able to run at a shuffle pace, and even caught the woman who'd said she was going to wait for me. I thanked her for the inspiration.

Cara was at the turn to the final meters before the finish... she's said she might leave after completing her hike, but she'd waited, and that made me happy. I turned the corner, ran to the finish line, and I was done... completely. I collapsed onto the ground and lay there, not wanting to move.

first climb
Finish (Cara Coburn)

Cara told me my time was 3:08, not much off my 3 hour target (official time was 3:08:30). I was amazed by this, as the wrong turn alone had clearly cost me more than 8 minutes, and my collapse toward the finish had been rather dramatic. When results were posted, I was 18th overall, not too bad at all, although I'd been hoping for a top 10.

But running's more about the feeling than it is about the hard numbers. That feeling of having delivered the best possible effort, to overcome discomfort and arrive at the finish strongly but with nothing more to give, is intoxicating. Here I'd failed in reaching that goal. Of course the extra distance from missing that corner didn't help: the extra km get tacked onto the end of a race, not the middle, and there was a very high rate of interest paid on that extra bit of running. Still, I finished, and placed fairly well. It just left me wishing I could try it all again: not go into the race is a partially weakened state, and not trust people to know the way just because of neurotic navigational inferiority complex. It's ironic that of the four Coastal Trail Runs I've done, on the three on courses I've "known", I've taken wrong turns (in two cases following people), while on the one on a course I didn't know, I navigated without error.

The run left me feeling totally wasted. My muscles sore, my energy spent. Here it is Tuesday, three days later, and I'm finally feeling a bit better. At least I can start walking from seated without a limp. Maybe I'll ride my bike to work tomorrow.

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.

Monday, July 18, 2011

Voeckler on Plateau de Beille: 2004 and 2011

A lot has been said and written about Voeckler's remarkable climb to Plateau de Beille in stage 14 of this year's Tour. Voeckler had an advantage of 1:49 over second-place Fränk Schleck, 2:06 over Cadel Evans, and 2:18 over Fränk's brother and teammate Andy Schleck. Due to time and fitness lost in a crash, race favorite Alberto Contador was 4 minutes down. Any of these riders were considered a threat to overtake Voeckler, although the consensus most likely scenario was Voeckler would limit his time losses and hold onto the yellow jersey by maybe 30 seconds.

Strava KOM: around a half-hour slower than Voeckler's time.


Yet it's safe to say it was a shock to almost everyone when Voeckler not only held on to his lead over all other contendors for the yellow, but was a primary activist in chasing down attacks. I'd have expected Voeckler, by any reasonable measure outmatched in that group, to take a very conservative approach to the climb, following the smoothest wheel to avoid going into the red for even a few seconds. Cadel Evans and Alberto Contador are both exceptional in their ability to put on short bursts of amazing climbing speed. So if Andy Schleck attacked, Voeckler could have let one of these riders close the gap, perhaps following Basso who would steadily bring it back together afterwards. But instead Voeckler was sprinting back to Andy's wheel himself.


Voeckler's special motivation on the climb.


Meanwhile, Andy was tempering his attacks based on what was evident weakness in his brother. Fränk obviously wasn't feeling as frisky, and the risk was an attack by Andy could result in nothing more than Fränk getting dropped from the group. That would hardly serve his team's interest. Of course, best of all would be for Andy to attack and get away solo, something a lot of his fans obviously wanted to see, but Andy had a good view of how his brother and the others appeared, and if Fränk was a weak link, he may have realized the team would do better by staying united at least until the upcoming Alpine climbs.

All of this start-and-stop worked to Voeckler's favor. Voeckler is also a punchy rider with a strong top-end, but where he'd have most likely succumbed would have been a faster, steady pace. The lack of cooperation among the favorites also allowed first Jelle Vanendert and later Samuel Sanchez to ride away from the group -- Jelle is out of overall contention and Samuel, although now 6th overall, is a poor time trialist and so still needs to gain considerable time in the mountains to be considered a threat. So by cooperating the favorites obviously could have climbed faster, likely faster than Voeckler could have sustained. But dropping Voeckler wasn't the priority, since Voeckler also is considered weak in the time trial, and so I don't believe the favorites consider him a likely threat to still lead in Paris.

Science of Sport
Science of Sport plot of great VAMs in Tour history. Voeckler's 1600 on Plateau de Beille is well off the chart.


This is all deja-vu for Voeckler, who also rode to defend his yellow jersey seven years ago on the same climb. He finished that stage 13th, 4:42 behind Lance Armstrong and Ivan Basso, to just hold on to his yellow.

So what is it that allowed Voeckler to go from a rider who got dumped by close to 5 minutes by the favorites to one who was in the mix, matching their accelerations to the end?

Michele Ferrari named and popularized the use of the VAM metric: the rate of altitude gain of a rider on a climb, typically measured in meters of altitude gained per hour. It's a decent way to objectively compare rider power/mass ratios, especially when comparing climbs of a similar grade and altitude difference.

The results: Vanendert finished the climb in 46:01, a VAM of 1627 m/h. Samuel Sanchez was 20 seconds slower, then the favorites finished Samuel Sanchez was not far behind (20") and the group of favorites did it at 1600m/h (5.75 w/kg), in 46:48.

In contrast, according to Wikipedia Lance Armstrong reportedly did the climb in 45:30 in 2004, and Marco Pantani climbed it in a remarkable 43:30 in 1998. In 2004, Voeckler finished 4:42 behind Armstrong, making his time 50:12.

So it appears Voeckler was able to take 3:24 out of his time from seven years ago. But the stage in 2004 was 206 km ridden at 33.8 kph, with seven rated climbs:

2004 stage


In contrast, this year's stage, while still extremely tough, was clearly easier: 168 km with six rated climbs (CyclingNews) ridden at 32.2 kph. That's 1.6 kph slower than the 2004 stage, which had an extra category 3 climb. So it's reasonable Voeckler would be faster this time.

2004 stage


It's no surprise the speed was higher in 2004. The finishing list looks likes a who's-whom in mid-naughts doping scandles. Of the twelve riders finishing ahead of Voeckler only the last, 12th-place Stéphane Goubert, has not been involved in a major doping scandal. I think it's safe at this point to include the stage winner in the "involved" category, given the consistency and number and specificity of charges against him. So it's really remarkable Voeckler was able to hang with that crew as long as he was without totally collapsing on that final beyond-category climb.

Anyway, Voeckler's weakness is his time trial, and thus I think he has little chance to win the yellow when the Tour arrives in Paris. And while a VAM of 1600 was enough on the tactical shadow-boxing on Plateau de Beille, it's unlikely he's going to be able to follow a more sustained attack during the back-to-back big stages in the Alpes.

added : Cyclocosm has an excellent comparison of times, which differ slightly from Ferrari's (it depends on if you time the group or the individual riders, since it takes a significant time for the pack to cross the threshold of the climb).

Sunday, July 10, 2011

Specialized Venge and Mark Cavendish

The Specialized Venge made its debut at Milan San Remo this year, and it couldn't have gone any better for the Morgan Hill company, as Matt Goss, a relative underdog, won the race. Move on the Tour de France, and with aerodynamically optimized mass-start road frames more popular than ever, Mark Cavendish has pulled out two impressive sprint victories on the bike in a first week notably unfavorable to sprinters. Last year when HTC was sponsored by Scott instead of Specialized, Cavendish rejected his Scott Foil (then F01) in favor of his tried-and-true super-beefed-up Addict, so once again this looks good for Specialized.


Venge spotted at Mike's Bikes in San Francisco


But the frame is only a relatively small part of the aerodynamic picture. Far more important is body position. So here's photos of Cavendish during his two victories this year... first stage 5:

CyclingNews
CyclingNews


Then stage 7:

CyclingNews
CyclingNews


These photos aren't cherry-picked: they're the first ones I found on CyclingNews of the respective sprints in the final 100 meters or so. Just look at Cav's position: the top of his helmet is hardly higher than his back. Sure, some other riders can be seen with low head positions, but that's with their faces down, not sustainable. Cavendish is always looking forward, never down. He's watching where he's going.

Here's a shot from Mark in 2009 outsprinting Thor Hoshovd, Oscar Friere, and a Milram rider (Ciolek, I believe). Look how vastly superior his position is to his competitors:
2009 Tour de France
Associated Press


It's often said sprinting is about raw power. Yet Cavendish's power is easily overestimated. It's been reported that Cavendish doesn't "test" well, and that in sprints he produces only around 1300 watts, a non-spectacular number. Of course, he's producing that power at the end of a long difficult race, after finishing with several kilometers over technical roads at close to 60 kph sustained. But the guys he's beating consistently can also put out power under the same circumstances. Cavendish wins not because of superior power, but because of superior speed, and except under the most exceptional circumstances most power goes into wind resistance.

Look at a Tour finish and the final 200 meters aren't enormously faster than the 200 meters preceding. Cavendish, for example, has Mark Renshaw, a man who's won Tour sprints himself, leading him out with his own maximal effort. No -- the sprint of a Tour stage, in addition to critical factor of position, is a time trial, and time trials are won by power balanced against aerodynamics. Cavendish is so unprecedentedly successful because he has one of the all-time great sprinting positions in professional cycling history... to beat him you've not only match his power but substantially exceed it.

The aerodynamic frame is icing. But the primary factor in aerodynamics is body position. 100% of great time trialists have great body position, going back as far as photographic history records. And Cavendish looks like a time trialist when he sprints. That he's able to hold that poise in the midst of so much chaos is remarkable.

Wednesday, July 6, 2011

Golden Gate Park Bicycle Lane Proposals

San Francisco has posted a survey on preferences for bike lanes on JFK Drive in Golden Gate Park. The candidates are independent bike lanes in the direction of traffic flow on each side of the street or adjacent bike lanes in each direction on one side of the street. In each case the lanes would be 6.5 feet wide with the buffer at least 5 feet wide. Vehicle parking, where present, would be outside the bike lanes (further from the curb).

Here's the configuration with bike lanes on each side. The schematic shows car parking on one side of the street. In other sections of the road there would be insufficient room for any parking, and the buffers would be wider:


Here's a schematic of the configuration with the lanes on the same side, in the case where car parking is on the same side as the lanes (the parking could also be on the opposite curb):


The San Francisco Bike Coalition has promoted the one-sided configuration. They publish artists renderings of cheerful cyclists pedaling in the sun in green-painted lanes. It's part of their "Connecting the City" campaign.

Connecting the City

However, there's two serious issues with the one-sided configuration. One is that at some point the lanes end. At each end, one direction must transition between the left and right of the road. This requires first crossing on-coming vehicular traffic, then merging with cars moving in the same direction. Usually when you merge with traffic, you look over your shoulder to make sure it's clear, but since you're facing on-coming car traffic at this point looking backward must be done with exceptional care. Even with a mirror, which reduces the head movement required to look back, your attention is removed from the on-coming lane. The same problem occurs for cyclists making left-hand turns: doing so requires crossing first the on-coming bike lane, then an on-coming vehicle lane, and finally the lane of car traffic moving in the same direction. There is enormous opportunity for failure here.

Another problem with the one-sided configuration is pedestrians, who in the park are often distracted tourists or children, must now check for bikes from the left, then bikes from the right, then cars from the left, then cars from the right in order to cross the street. With the lanes on each side of the road, cars and bikes are from the left, then cars and bikes are from the right. This latter case is the one which we've been trained most of our lives to handle. I don't have statistics to back this up, but it seems an inattentive pedestrian is at fare greater risk, and presents a far greater risk, in the one-sided configuration.

The two-sided configuration isn't great, either. With the bike lane between the parked cars and the curb, drivers moving between their vehicles and the side of the street need to watch for bikes. I'm not too worried about this: the 5-foot buffers should help. But on the 2-sided scenario cars may be parked on the side opposite the bike lanes.

So what's the solution? Of the two, I far prefer the two-sided set-up. And the much-neglected California Highway Design Manual chapter 1000 (PDF) agrees:

Class II bike lanes shall be one-way facilities. Two-way bike lanes (or bike paths that are contiguous to the roadway) are not permitted, as such facilities have proved unsatisfactory and promote riding against the flow of motor vehicle traffic.

Sure, the two-sided plan results in the loss of additional car parking, but car parking is not and should not be the priority here. The roads are primarily for transportation, and space is too precious in the city.

This may be controversial, but the City Charter has since 1978 been quite clear on the matter: San Francisco has a transit-first policy. But "transit first" doesn't simply promote mass-transit: it prioritizes all nonvehicular transportation. It's really worthwhile reading the whole thing, but here's an extract:

8A.115.3: Decisions regarding the use of limited public street and sidewalk space shall encourage the use of public rights of way by pedestrians, bicyclists, and public transit, and shall strive to reduce traffic and improve public health and safety.

This cuts straight to the core of the JFK issue. There's two reasons to allow cars in the park. One is to allow drivers to access the park itself. The other is to provide transportation from one side of the park to the other. But the presence of the cars here actively impedes park users who aren't in cars. Cyclists and pedestrians are not only endangered by all of the vehicles, but the noise from all the auto traffic spoils the tranquility which should be provided by the precious resource which is Golden Gate Park. If we want to encourage access by pedestrians, bicyclists, and public transit, if we are striving to reduce traffic in the park and improve public health and safety, the obvious approach is to extend the Sunday daylight restriction against motor vehicle access to JFK to 24-7. There's other roads into the Park, like Kezar and 19th Ave. JFK serves no critical purpose other than to facilitate and promote automobile use.

New York City is way ahead of San Francisco in many ways, and this is one of them: cars have been restricted from Central Park (except for 4 hours per day M-F) for many years. San Francisco need only follow its example.