I can't help with any specific software, although I'd be interested in knowing if any existed as well, BUT, I can add that we average about 50 mph on the road when travelling on highways 60-65 mph. The 50 mph average includes fueling stops, walk the dogs stops, and stretch your legs stops. Sometimes those are combined. We usually don't stop to eat as we have prepared meals we eat while travelling down the road.
You might be able to use the 50 mph as a guide and adjust it accordingly to the speeds and style of travel.
~Rick