Speed Govener's

I wonder if a variable speed limiter could work? Like say once an hour you can have 70 or 75 for a period of 30 seconds for passing purposes?

I know Volvo's can be setup to reward the driver with an increased speed limit for a short amount of time if they can meet target avg. fuel economy set by the carrier.

I didn't understand because I'm not a real driver yet. I've only spent a limited amount of time driving a rig on the highway and it was local.