The growth of China's High Speed Rail network

[George Harris]

The issue with transit in the median, in cold climates (or moderate climates with snow), is the salt and salt spray thrown up by salting highways in winter. It's caused a lot of problems for the CTA over the years on all of their lines that run in the median.

Which is why Union Pacific (or was it Southern Pacific before their takeover by UP) gave up on maintaining signals on their line across the Great Salt Lake. It now runs without signals. The salt spray kept shorting it out. By the way, salt water also significantly shortens rail life.