The Tour de France threads brought this to mind. How do they time bike races nowadays? From personal experience, 5K running races are often timed with electronic chips that go on your shoe – do bike races use the same basic technique? Or are the racers spread out enough that you can time it manually?
I’m not just interested in pro level races (with unlimited budgets), but also recreational/local weekend ones.
You’d see the cables they run over if the shoe-chips were used. Since these aren’t visible, it must be an official timer at the finish. Keep in mind that it’s not as difficult as it seems since riders finishing in a pack all get the same time, even if they’re technically several seconds behind.
As John Mace said, the peltenon (the pack of riders) all get the time of the lead rider in the pack. This accounts for the majority of the riders. Any group gets the same time as the lead group rider, so you don’t need to time each rider individually.
How precise is the measurement of this 1 second gap between packs of riders?
Tangential question: How do the bonuses work? Do they deduct x, y, z number of seconds off the 1st, 2nd and 3rd place finishers, respectively, after every stage? Does the time bonus vary to reflect (and compensate) stage difficulty? What is the rationale behind it? Make the race more exciting? Place a premium on sprinting ability, perhaps?