There's a new article in Time: Off the Interstate: Turning 'Blue Highways' Green
The idea is that across the U.S.A. are side roads which were bypassed by the Interstate Highway System that are still there and underused. Some have proposals in the process to convert (?some of?) these side roads into some kind of green highway for EV's and bicycles. The Time article makes it sound similar to the "rails to trails" projects that convert old railroad lines into hiking and biking trails.
They point to small towns that used to be vitalized by the old highway system, but are largely abandoned and crumbling. They claim these small towns could have a resurgence.
It would take some laws to redesignate the roads to have a maximum 35 miles/hr speed limit. One thing they return to again and again are the "tens of thousands" of NEV's being sold, and how they could plausibly be used in the countryside if only the laws allowed them on the road.
The Time article claims the main page for the movement is: http://GreenInterstate.com/
Rails to trails is a terrible idea.
With climate change and the environment becoming toxic in more and more states across the country we need MORE rails not fewer.
I'd prefer us going the opposite direction: get rid of the interstate highway system and local freeways entirely. Build PRT lines and high speed rail lines interconnecting the states.
Rail improvements would be good, but, existing commuter trains need to expand their services to include "ferry cars" for bicycles, recumbents, ev-scooters, or rails will still not help many, unless other mass transit is expanded to cover the destinations. People value highly their independence, rather than wait while the bus stops at every corner. The open road still has appeal.