This is not a new problem, and has in fact been going on for decades.
A significant contributor to the problem is the cul-de-sac layout of so many of Fairfax County's neighborhoods.
Rather than the highly connected streets of a more traditional grid pattern, which creates alternate routes for traffic to flow, developers use the cul-de-sac pattern to maximize the available home sites on a given tract. Home buyer preference also plays a significant role: many people would rather live on a quiet cul-de-sac than a busy neighborhood street.
What this means is that when people want to leave their neighborhood to go to work or go shopping, all that traffic is funneled through one or two exits onto a single primary or secondary road. There's no back route for them to take.
The problem is further compounded by traffic control measures, such as speed humps or conversion to cul-de-sacs, that many residents demand on their residential streets because they don't want a large volume of traffic flowing through their neighborhood, which is wholly understandable.