I've lived in and around DC for going on 20 years now. In my opinion, Saturday morning is 2nd best overall for traveling through the mixing bowl that is DC/MD/VA--Sunday morning would be the best. 8AM on Saturday would be fine, earlier, of course, would be better, but later would definitely be less desirable. As mentioned earlier, accidents would be the exception, but that can happen anywhere on 95 from Maine to FL.