Another day, another high-speed rail analysis. Designing a line for Massachusetts was difficult for two reasons. In the eastern third of the state, sprawl is almost continuous. In the western half, there is again sprawl around Springfield, and then an area of very jumbled geography. None of the mountains are particularly high, but at the same time there are no large, level valleys that can be used to approach the highest peaks. Anyway, in the eastern half or so, the best solution was to parallel I-90. Following the current CSX alignment wasn't possible because it runs through the center of so many towns. In the west, because of the built environment west of downtown Springfield, a detour to the south was necessary. After that, it was a matter of finding the least bad route until the rail line could meet up with I-90 again. To keep speeds up, several tunnels and viaducts were needed.
I think the main takeaway from this exercise is how restrictive the sprawl around American cities can be on new transportation construction. Most existing rail lines were first laid out in the 1800s, and the Interstate Highway System was planned in the early 50s, when the population was half of what it is now, and much less suburban. Projects planned now, unlike those other two, have to deal with a built environment that is fully built up within a 20 mile radius of large city centers. And large city centers are where high speed rail lines need to go.