I agree with the person who said to compare a month each of driving to biking. The test isn't accurate/fair if they don't do that. Big surprise
Anyway, I usually CHOOSE to ride where there is less traffic. Granted, the city I live in isn't hugemongous like NYC or something, it's a smallish city, so it may not be such an issue, but the roads that have less traffic also have better scenery! I ride as much for that as anything else. You just can't really look at stuff going by at 50+mph. I'd choose the nicer+safer route over the faster one any day.