User blog comment:Mr Procrastinator/Length of Drag Races/@comment-26249703-20160217160349/@comment-26329136-20160217182937

I just use endurance events to find out lap lengths. It's not exact but it's accurate to less than 10m or so. I did that to find out lap distances for my How often does a car need servicing blog.

If a track has a NASCAR race on it, you can ram another car to wreck it and then park next to it to measure distance. I just tried doing that on Indianapolis Speedway track and got a distance of 4,032 m. The endurance method has a distance of 4,030 m.