I did a blind analysis of an experiment about drafting another cyclist at 12 metres:


http://alex-cycle.blogspot.com.au/...2/pour-me-draft.html

In short, this rider attained a significant reduction in power demand at 40km/h.
~ 30W in still-ish air
~ 20W with cross winds

Not nearly as big an impact as the car convoy following the race. Anyone who drops back can now easily get back to the peloton. In pure bike racing you get dropped like that, for whatever reason, and the day is over. But not in all the big pro races![/quote
Not sure you've experienced what actually happens in pro bike races. I speak with experience as a UCI world tour accredited convoy driver and the impact of vehicles is minimised wherever possible. There are specific protocols in place for this.

In bike races with vehicle convoys, if riders are dropped because they can't keep up, as opposed to having a mechanical or simply going back to the team car for a chat or to collect bidons, then commissaire vehicles create a barrage preventing team and other vehicles from filling the gap. It means that any such riders must cross the gap under their own steam.

Once the gap is large enough, the commissaire will permit a few vehicles to pass but not so many as to fill the gap and give advantage to the dropped riders. As the gap grows, so more vehicles are permitted to pass.

If a chasing group is making ground back up on a peloton with following vehicles, eventually the commissaire will require the vehicles following the peloton to pull over to ensure the chasing group does the work on their own.

Commissaires are constantly monitoring the gaps and managing the team cars and other vehicles in the convoy. It's actually one of the biggest elements of the work they do during the race. As a driver you work along with the commissare to help execute these race protocols, and much anticipation of the race situation is required - it's a very dynamic beast at times.

For riders who have suffered a mechanical mishap or a crash and then restart riding, then commissaires don't generally consider that a reason to form a barrage since it's "no harm, no foul". There are limits of course to the amount of assistance a rider may receive and riders are required to make progress back - they may not simply stay within the convoy.

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http://www.cyclecoach.com
http://www.aerocoach.com.au

Yep I read your post a long time ago along with other stuff of the years. I don't feel it is that much at all. Truthfully I can't really notice any difference at 12m, if it is a cross-wind then definitely no difference. The problem is it is just too much hassle to space at 12m. Any more and someone can slot in, any less and you open yourself up to subjective penalty. Would just be much easier at 20m.