For me, i think either all T or all M...more pratical.
All T... I suppose this would be a linear (or gravitational?)
concept? There must be at least a motor car on a train.
All M, I also thought of this once. Not until I saw materials
about All M trains, other than the Shinkansen/high performance
trains.
Local (slow to moderate speed) trains tend to carry lots of
passengers. With a All M configuration on a heavily loaded train
(200 percent load factor), the power draw would be huge. So much so
that voltage drops and performance of the train/other trains will
be compromised.
Hence All M configurations have largely been avoided. However
for companies with large infrastructure, good substations and power
lines/supply, this poses little/no problem.
