Today's time trial was hilly, with two uphill and two downhill sections. The roads were narrow and twisty in many places, including several switchbacks and a downhill section through a town where it would not be possible to practice the turns beforehand due to traffic. On each turn, the riders are faced with a choice: slow down to be sure not to crash, or take your chances and maintain velocity through the turn. With so many turns, speeding through all of them might save a total of a minute or maybe even two, out of an hour and 15 minutes or so for the whole stage. That's more than the winning margin for the stage, and comparable to some of the overall placement margins. But crashing costs minutes, and affect your rhythm after the crash as well. So in addition to the problem of how best to pace himself for a long effort, each rider must decide how to approach the turns -- a calculus which can change over the course of the race.
To understand how the riders today rode the way they did, let's look at what each of them is trying to achieve.
Lance Armstrong came into the stage with a healthy lead over second-place Ivan Basso. No matter how either of them ride, that's not going to change. But he'd like to win the stage, since he hasn't won one yet this year. If he does win, he doesn't care by how much. So Armstrong starts out willing to take a fair amount of risk, because the upside is a stage win and the downside (a crash) would not cause him to lose the overall lead. He's not worried about crashing twice, because after the first crash he'd stop taking risks to get the stage win, and would still be assured of losing less than two-and-three-quarters minutes to Basso.
Ivan Basso in turn has a good lead on the riders behind him, and isn't worried about losing his second-place spot as long as he doesn't crash. But he doesn't have as big a cushion as Armstrong does. He'd also like to win the stage if he can, but it's not really all that likely, and it's even less likely that he'd depose Armstrong. So Basso is not going to take any risks at all on the descents. But we can expect him to do well on the climbs.
Mickael Rasmussen, in third place overall, is worried about losing his 2-minute, 12-second lead over Jan Ullrich. He's not a strong time trialist; if it weren't for the tight corners he'd expect to lose a little less than 3 minutes to Ullrich. So he's motivated to take every chance he can; it's the only way he might still be on the podium in Paris.
Ullrich, in fourth, has his sights on Rasmussen and on the stage win. So he too is going to be taking a lot of chances.
Bobby Julich, way back in 18th place, wants to help Basso (his team leader) retain his second place. He can't do this directly, but there's a subtle way he can help. Basso won't know how far behind Armstrong he is, because Armstrong starts last. So Julich is going to ride a very good time trial, to give Basso something to compare himself against. This means not taking any risks, partly because Basso isn't going to, and partly because if he crashes then there's no reference. Julich and Basso are both followed by team cars with GPS, which can provide Basso with real-time information on how he compares to Julich at any point along the course. Basso also knows how Julich is feeling, and rides with him enough to know how Julich's strengths and weaknesses compare to his own, so he has a very good idea how his time should compare to his teammate's.
Armstrong and Ullrich also have teammates whose jobs it is to provide a reference. But Julich did the best job of that today. So let's use him for a reference too (instead of comparing to Lance as everyone else does), and see how everyone did.
At the top of the first mostly-uphill section, Basso held the lead, having picked up a surprising 41 seconds compared to Julich. Armstrong has 34 seconds on Julich, and Ullrich 24. Rasmussen has crashed, and lost 94 seconds, which is about a minute more than he would have lost without the crash. Ullrich now knows that third place overall is assured, and is considering the stage win. Basso, though, doesn't know yet that he's picked up time over Armstrong, so he's sticking with his no-risks strategy.
At the bottom of the first mostly-downhill section, Armstrong has picked up 26 more seconds, and Ullrich has picked up another 17 seconds. Basso, riding conservatively, has lost 34 seconds out of his 41-second lead. Rasmussen has crashed again, and since his chase car only had one complete bike he's had some mechanical trouble; he has lost 233 more seconds, which is about three and a half minutes more than he'd have lost without the crashes.
At the top of the second uphill section, Armstrong has picked up another 28 seconds, Ullrich has picked up 15 more seconds, Basso has gained 3 seconds, and Rasmussen has gotten past his mechanical problems and only lost another 31.
At the bottom of the second downhill section, Armstrong has picked up 10 more seconds on Julich, Ullrich 7, Basso (still descending conservatively) has lost 22, and Rasmussen has lost another 42. Armstrong is now over 30 seconds ahead of Ullrich and it's near the end of the stage, so he's going to cut back on the risks he's taking.
The stage ended with a flat section, over the course of which Ullrich gained 7 seconds, Armstrong lost 5 seconds, Basso lost 9 seconds, and Rasmussen lost 36 seconds. Rasmussen is now just over five minutes behind Ullrich in the overall standings, four and a half of which he can blame on his crashes. We were expecting him to finish about 45 seconds back overall, so all those risks he took probably only got him about 15 seconds, because Ullrich was also taking risks. But Rasmussen could have gotten lucky, or Ullrich could have gotten unlucky (especially since he might have taken more risks if Rasmussen hadn't crashed), and so there was some chance; it was a gamble worth taking. Basso's conservatism has had the expected result; he is still in second overall. Could he have gotten the stage win? Maybe, but maybe he'd have crashed, and Ullrich finished less than two minutes behind him in the overall standings so the risk wasn't worth it. Ullrich has accomplished his goal of moving up to third, though he hasn't gotten the stage win. Armstrong's gamble has also paid off; he finished 23 seconds ahead of Ullrich for the stage win, and didn't have to do anything dangerous in the final miles.
So yes, it's a shame that Rasmussen crashed. But it's not the surprise that you might imagine it was by reading the papers.