Route 1 seems like a local-road to me with lots of traffic lights though.
I-95 works really well as long as its clear. But as soon as an emergency happens, the spillover traffic is too massive for Route 1 to ever hope to handle. An interstate-highway can't rely upon a traffic-light laden local road to handle the traffic from a 4-lane interstate.
EDIT: In the case of the 2017 eclipse, the traffic was so heavy that truckers started to pile up on the side of the roads (allegedly due to the laws stating that they could only drive for X hours at a time). Losing a few lanes slowed down traffic dramatically, causing even more truckers to just pull over due to legal requirements. I don't think the GPS / Waze ever recommended for us to leave I-95 during this time, so Rt. 1 was never a consideration.
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A 2-lane highway without traffic lights that runs parallel would help a lot. I don't know the lay of the land in Virginia (ideally such a road would be coordinated with local suburbs / local cities to lessen day-to-day traffic as well).