Does anyone know of a website that would let me view average traffic for specific times in a big city?

I have to go into Charlotte tomorrow evening and I’m trying to get an idea of how much traffic to expect/how much of an early start to give myself. The free parking where I’m going doesn’t open until 6, so getting there too early is not good. I’m sure there has to be a website that has this kind of data, especially with all the traffic servers out there. If this doesn’t exist yet, can one of you other web developers work on building a good traffic map? mmkthxbai