Think [MENTION=24635]Greg Bobkin[/MENTION] might have been looking at the other Centurion link (piece of string race).......
Good question. It was interesting doing the Amex Marathon a few weeks ago with the elite runner that was in the field - he was very clearly and obviously taking the 'racing line' on the inside all the time, to the extent he was calling ahead to people to move out - I hadn't thought about it previously but obviously the decent runners know what difference it makes on lapped events. Just an extra 10 yards every lap in a 24 hour track ultra for an elite ultrarunner would cost them over 6km if my calcs are correct (ie they'll have run 6km further than the results given them credit for)
Each lane is 7.665m longer than the one inside it. The difference between the inside line and outside line of each lane would be almost 7.665. So straying from lane 1 to the outside of lane 2 would be 15.331m. As you say a huge difference.