Idling downhill costs less gas but may lead you in the wrong direction for a short while, vs going over a hilly route where you must accelerate uphill more ofte

Idling downhill costs less gas but may lead you in the wrong direction for a short while, vs going over a hilly route where you must accelerate uphill more often. As a simple, unimaginative example. I'm sure you can think of others if you put in the time.