Actually, it's when someone can figure out how to make meal service on trains profitable. Most Amtrak routes without meal service makes operating profits, and only one or two routes with meal service might make an operating profit.
Given current train speeds, that comes out to around 500-700 miles being the upper limit of viable HSR. This is roughly the distance between Chicago and DC and also roughly the distance of the largest axis of most European countries.
Given current train speeds, that comes out to around 500-700 miles being the upper limit of viable HSR. This is roughly the distance between Chicago and DC and also roughly the distance of the largest axis of most European countries.