Nice option that would be.
But even nicer I do find the option between 'fastest' and 'shortest' maybe called 'optimal'?
Some car navigation systems offer this and calculate the route fast but keep in mind short-cuts that are shorter (but take more time).
So gor carlos example
fast 35km 27min
short 30km 30min
I would not drive 5km extra for saving 3 min.
But maybe there is route in between like
optimal 32km 29min?

--edit
have used the car mavi today and the option was
called 'efficient route' not optimal
it tries to save kilometers but still going fast