If I understand your explanation correctly, then the need for hysteresis is removed too... Nice!
That got simplified out in the discussion, but would still a good idea, and would be handled by the GPSapp algorithm... Following on from the hypothetical scenario earlier, the transitions should occur:
mph.
(0) - set 'base' volume to -10dB
30 +1 step
40 +1 step
50 +1 step
60 +1 step
(65) 'base' volume changed.
50 -1 step
40 -1 step
30 -1 step
20 -1 step.
This would allow us to cruise within a 10mph band without the volume constantly changing.
_________________________
Mk2a 60GB Blue. Serial 030102962
sig.mp3: File Format not Valid.