US Route 1 is already an interstate highway with 4+ lanes through the area you're talking about. Development was encouraged down the I95 corridor since its creation and the density that has resulted pretty much makes this unavoidable. There was a similar situation with the Woodrow Wilson Bridge on 495 outside of DC in 1998 when it was closed due to a jumper during afternoon rush hour, and the traffic jam lasted overnight despite there being alternate major routes in every direction. The problem is that the bridge carried more traffic than all of the alternate routes put together (I'm assuming based on my experience).

https://www.washingtonpost.com/wp-srv/local/longterm/wilson/...