nowadays, it is no longer appropriate to always display the fastest route as the default.
just today waze wanted to send me from a 25.2 km route to a 49.9 km route because it was 5 minutes faster. I think 14% time savings for a 58% longer and thus a more material- and environment-harming route, not appropriate!
in addition, vehicles consume less fuel when they drive slower (39 vs 70 km/h average in my example)

There should be a user-value in the options with defines the accepted time-distance-tradeoff. In my case a value of about 3 km/min would be accepted: I save 3 km, if i drive 1 min longer.