I've taken part in road rallies that technically observe the speed limit.
Times at Marshall points are calculated based on your departure time, and a calculated time between them -based on achieving an average speed that does not exceed the speed limit.
... Fact is I've never driven so hard for two hours straight as I did then... Clutch cooking and brakes fried... Averaging the speed limit on English B roads can be pretty tricky!
... Whoever is closest to their target time wins...
Not sure if this is the same thing as you're talking about, but its a road legal rally, and they aren't uncommon here.
