The flat terrain helps with the smooth traffic flow.
You can build roads anywhere, unlike Pittsburgh where everything funnels to "The Point".
The Point is, among other things, where the three rivers meet, where the French built Ft. Duquense which led to the French and Indian War and where Lewis & Clark launched their flatboats for their famous expedition into the newly acquired Louisiana Purchase. So it has been a site of traffic congestion for a long, long time.
LOL. You are suggesting that Lewis & Clark created the first traffic jam in Pittsburgh? It's been a traffic mess ever since.