If a 55 mph road usually sees traffic flowing at 60+ mph most of the day, but everyday it slows to 35 mph at the same time, Waze will do two things:
1.) It WON'T ask if you are stuck in traffic
2.) It WON'T draw a line on the map showing traffic
So that seems to be what you are asking for. Waze just needs enough historical data to be sure that the slow down is "normal" for the time period (in 10 minute slices).
Note: quite a few Wazers actually hate this method and want to know everytime a road is flowing slower than its all-day average. Personally I like Waze to hide "normal" traffic otherwise every single road will be red at rush hour in most major metro areas