First, consult a clock. Is it rush hour? If so, you will have traffic. Is it three hours before rush hour, but a Friday afternoon? Then you will have traffic. Is it any time after noon on a Friday before a long weekend? You will have traffic, and a lot of it, especially in the summer.
Next, consult a calendar. Is it a federal holiday? You will not have traffic, because everyone else is at home. Is it a Friday morning? If the other signs are in order, you will not have traffic. Is it the weekend and the morning? There will not be traffic, but beware: traffic increases throughout the day, even on the weekend, and especially if there is a Redskins game or Jimmy Buffet concert.
Look out a window. Is it raining? There will be traffic. Is it snowing? Just stay off the road. Has there been ice? Poor benighted fool, you will labor under a curse for the rest of the day.
Then, turn on the news radio. Is your principle route the first road they mention in the traffic report? You may wish to pull off the highway and have a coffee and danish if this is the case.
Finally, consult the heavens above. If you see one helicopter hovering over the road ahead of you, all may yet be well, but your chances of traffic are increasing. If you see two helicopters hovering, there will almost surely be traffic. And if you see three or more helicopters hovering, be prepared to move aside to make room for the emergency vehicles which will need to get past your parked car.