I was driving home from my Dad's today right around 1630. Just the beginning of rush hour on the expressway. I'm zipping along all happy and content then one of those lighted signs display, "Expect delays, traffic congestion ahead." Okay, sure enough, the traffic slows to a crawl. Stop and go traffic. Inching along for a good mile or mile and a half. Then suddenly, the traffic is free flowing again. What was the hold up? There were no entrance or exit ramps, no construction. What causes that congestion? It was so weird.