Not sure about past years but this year the Main drag WAS closed to all traffic. The roads one block over on each side are still open and they are kept at a slow pace. It seemed like they had thru traffic rerouted around the town. There are quilts on the side streets as well. It is pretty impressive to see it all the first time.
If you get there a little early (9ish), the traffic really wasn't all that bad. Maybe 3-5 blocks? You can find a spot to park near the fire station and there is a nice picnic park right there with lots of trees to shade you.