Looks interesting. The ETA in mu Garmins have always been pessimistic but I have found at the end of the day they work out almost spot on since they do not do not factor in fuel and lunch stops.
I wonder if the Waze app realizes that MSTAers (well most, anyway) go faster on twisty backroads where there are no popo than on the major highways where radar threats slow us down. A big flaw in Gar,im's "Fastest Rout" calculation.
Depends on the backroads and how wild of a rider you are. To me back roads = twisty and often with many small towns. That means lower than highway speeds, my GPS bears that out as does a friend and riding companion's bicycle computers used on his rides for years. Riding on back roads we rarely have a moving average above 40-45MPH. On the slab that would easily be higher, depending on the speed limits maybe close to double (80 in a 70MPH zone). Sure back roads have less police, but there's also more challenges for the rider.
If however your back roads are mostly flat and straight (Florida, Kansas, etc.) then sure the speeds may be higher.
In the years I've used GPS I've tried to understand the estimated travel time, even in the car it doesn't seem to make sense or depend much on the speed I'm traveling.