According to the INRIX National Traffic Scorecard Philadelphia/Wilmington Area congestion dropped 28% over the past year. However a deeper decrease in Atlanta kicked the region's congestion rank up from 12th worst up to 11th worst.
The Travel Time Index dropped 3% to 1.10 which means that a random trip at a random Time can expect a 10% increase in travel time due to congestion.
Which brings into the question the forecasting for traffic increasing, which is a major catalyst for building bigger roads. Granted high gas prices and a sagging economy may be a short blip in the projected trend. But with an aging population and the likely scenario that a surge in demand will drive up gas prices you have to wonder if current traffic forecasting models have any validity at all.