How fast is a team time trial?

HOW FAST IS A TEAM TIME TRIAL? On Wednesday's team time trial prologue of Tirreno-Adriatico, Garmin-Barracude entered the final kilometer with 17.57 on their clock. They crossed the line at 18:58 - a kilometer in 1:01. That puts their final kilometer at almost 60kph, just over 37mph, at the end of a nearly twenty-minute all-out effort that shed four of their riders. Their 18:58 time gave them an average speed of 53.4kph (33.2mph) over the 16.9km route.

HOW DOES THIS COMPARE TO OTHER DISCIPLINES? Well, the UCI's 1-kilometer track time trial record is 58.875 seconds, or an average speed of 61.2 kph / 38 mph for just under a minute - starting from a stop! And, the UCI's World Hour Record is 49.7 kilometers in one hour - averaging 49.7 kph, naturally, or nearly 31mph for an hour - three times longer than Garmin-Barracuda's Tirreno-Adriatico time trial, and with one-ninth the number of riders.

WHAT KIND OF SPEED DIFFERENCES RESULT IN TIME DIFFERENCES?

Greenedge, the winner, rode at 54.2kph - quite a bit faster than Columbia-Coldeportes' (the last team on the day) average speed of 49.6. But take a look at Saxo Bank, who finished 6th, just off the (extended) podium. They finished 8 seconds behind Astana, due to an average speed differential of just .35kph. And Lampre-ISD missed out on a top-ten ride by a speed differential with Lotto-Belisol of just .04kph.

Time trials pose great examples of the accumulation of marginal gains. A more aerodynamic position, a faster wheel, an unfavorable start position and changing weather - an extra half-kilometer-per-hour of speed all add up when the officials stop your clock. By charting these average speeds we can see where the slimmest margins are. Those who finished 6th through 17th all had speeds within less than 1kph of each other.

That looks like a pretty big drop in performance until we scale the y-axis all the way down to zero, more accurately showing the difference as a proportion of the overall (removing this "perspective" is one of the fundamental ways to mislead using statistics).

Weather and the Tirreno-Adriatico Prologue

Earlier today, Marco Pinotti tweeted, "Last 7 team to start are all in the 3rd part of final classification. Wind was a factor today." Following Monday's post I'm interested in the individual data that time trials generate. Can we see points of interest in graphing results?

A scatterplot of finishing order by starting position shows a noticeable upward trend (the green line is the least-squares regression line). Nobody who started in the last nine finished in the top ten, and BMC, a powerful team time trialing team, finished poorly and cited the weather. What does that tell us?

Compare that chart to a windchart from that day, below. Shortly after the time trial begins, the winds pick up, and halfway through the time trial, they switch from a crosswind to a headwind (most of the time trial was northbound).

NB: Starting order of a time trial is not without bias. Controlling for teams' innate difference in ability, and isolating the effect of the wind, would take a different effort.