I hit enter before I was finished, so here is another shot at actually answering the question.
When we went from (Liberty Harbor) NYC down to DC (Cherry Hill Park), we left out about 9:30 am on a Tuesday morning and hit little/no traffic until we got right outside of DC.
This was about halfway through a 45 day east coast travel tour that took us up through Va, to WV, Md, PA, CT, MA, NH, VT, ME, then back down through MA, RI, CT into NY, DC and then further south to NC, and finally to SC. We met friends there in SC and spent another week with them at the beach. We had a wonderful time.