Specifically for long trips: if I drive on a long trip (say, 10 hours at the speed limit, on high quality highways), given the fixed distance, how does my risk

Specifically for long trips: if I drive on a long trip (say, 10 hours at the speed limit, on high quality highways), given the fixed distance, how does my risk of a fatality change if I drive 20% faster and thus spend 2 hours less in the car?