The big dig was replacing an urban highway that already demolished much of the city and shouldn't have been there in the first place, and it shouldn't have been replaced. When you have land constraints the answer is easy: don't build for the car.

The way forward isn't that complicated. Electric cars don't fix most of the problems with ICE cars, and they'll need vast amounts of lithium and other materials to produce. We'll spend just as long replacing every car with an electric one as it would take to build out a decent amount of non car dependant infrastructure. And the way to do that isn't difficult either, just stop building new car dependant places, remove euclidean zoning codes, and start adding some transit and bike lanes. The dutch didn't get their bike infrastructure overnight, it was done by redesigning roads whenever they needed to be rebuilt anyway. The same can be applied elsewhere.