According to The Transport Politic blog it should be smarter to focus on few high speed lines trying to use them as much as possible to serve not only routes connecting stations served by HSL but also those cities linked to old lines which can benefit of travel time reduction on the high speed segment. Of course it is a giants’ war based on huge territories that would require amazing investments to operate in the next few years a wide net of bullet trains. TTP basically focuses on a scheme that results well balnaced in countries like Spain in spite of the double gauge net:
A large regional passenger rail network, operating at low-to-medium speeds (60-90 mph), must serve most of the country, reaching almost all destinations. This network could operate on cheaply upgraded freight track, which we in the United States are privileged to have in abundance.
A select few main lines, operating at high speeds (150-220 mph), should serve the country’s largest cities only, and the cities well positioned in between. This network would have to be built at great expense and virtually from scratch.
Trains must be able to operate on both types of track, so that trains can take advantage of high-speed segments, but can also serve smaller destinations not directly on high-speed lines.
[image: The Transport Politic]