It seems that Waze picks the best route at the time navigation starts.

With all the timing and route information that Waze and Google collects, it should be easy to calculate a good variance for the time of day.

It might be nice if Waze could display a midspread or "middle 50%" time, i.e. the time estimate for 50% of all drivers on that route at that time of day.

So maybe below the estimated arrival of "9:02", it would show "(9:00 - 9:15)"

It'd be even better if it took this into consideration when routing, like preferring a "9:03 (9:00 - 9:05)" over a "9:02 (9:00 - 9:15)"