42 C.F.R. § 414.617
For services furnished during the period July 1, 2004 through December 31, 2009, the amount for the ground ambulance base rate is subject to a floor amount determined by establishing nine fee schedules based on each of the nine census divisions using the same methodology as used to establish the national fee schedule. If the regional fee schedule methodology for a given census division results in an amount that is less than or equal to the national ground base rate, then it is not used, and the national FS amount applies. If the regional fee schedule methodology for a given census division results in an amount that is greater than the national ground base rate, then the FS portion of the base rate for that census division is equal to a blend of the national rate and the regional rate in accordance with the following schedule:
| Time period | Regional percent | National percent |
| 7/1/04-12/31/04 | 80 | 20 |
| CY 2005 | 60 | 40 |
| CY 2006 | 40 | 60 |
| CY 2007-CY 2009 | 20 | 80 |
| CY 2010 and thereafter | 0 | 100 |
42 C.F.R. §414.617