I usually try to avoid the Denver traffic Cluster-F**k, but to save time on my way home from the MB500 in Woodland Park, I just let my GPS get me home via the quickest route. When it routed me onto E470, I realized there would be some kind of toll, maybe a few bucks. But after a while I hit I76, and I don't remember any Toll Plaza, except at the exits. I just figured that through traffic got a break, until I got a letter instructing me to pay $29 or face eternal damnation. What did I miss?