[Mike Carr]

Using a given density altitude may work, but all tracks are various physical elevations. Houston, Gainesville and Sonoma for example (and a few others I'm sure) are 100' above sea level (physical elevation) or less. Maple Grove is around 550' above, give or take. Vegas is 2,100 or so. Denver is over 5,000'. So the number would have to be changed. -250' below sea level at The Grove would really be -700-800' below track elevation, whereas the same air in G-ville would be -300 below track elevation. And Denver will never see air that good. Neither will Vegas, Chandler AZ or Brainerd MN (Brainerd and Chandler are 1,200' or so above). SO you kind of would have a floating number, specific to each track, as far as what would be considered 'mineshaft'. At least this way NHRA introduced, the number is the same, regardless of track and elevation.