Responding to several matters raised since my last essay;
A). The mass of the locomotive is what protects the passengers in trailing vehicles.
B). In the Victorian context, there is not deemed any particular need to protect passengers against train - train collisions. Carriages have crash-worthiness standards, which as they showed at Kerang (3rd car) and Holmesglen (two sparks at fair speed) seem to work fairly well. let's face it, if two trains are going head to head at 160km/h each, you really cannot do much to protect the occupants apart from eliminating Pintsch's gas for lights and using steel instead of timber for the bodies.
C). A crew-cab vehicle leading a set of carriages with loco pushing behind has no greater issue at level crossings than any other train, providing those level crossings are closed or at least have active protection. If either of those two conditions are met, there is no reason not to use the driving trailers.
D). That UK idea of hand cranked level crossings seems ideal for the UK. Let's keep it there. Actually, if interlocked with signalling (so that signals are at stop when gates start to raise), then that would be OK as well, but the costs of such an installation in the Victorian context, where actually getting the power on site before you can think of boom barriers, signals, etc is huge. Think of the B. McCann crossing near Lake Charm; after a truck got in the way of a train a couple of years back, they have since installed boom barriers into what is effectively a private property which gets used for only a few months each year. They had to run electricity for over a km, using several poles, the line terminating at the railway. I doubt the power company would have done this as a charitable exercise.
E). Then there is the legal "system", where the truck drivers are not being successfully prosecuted for the collisions with trains. All sorts of defences are used, but if the same truck went through a stop sign at a road and collided with a school bus, how would the courts treat that? At Larpent, around 15 months ago, a truck derailed 475, and several passengers and staff injured. The truck driver got fined for not wearing a seat belt. The legal "system" is clearly not going to do anything to protect train users, so clearly the railways have to think that they are on their own.
F). Getting back to topic; the prospect of long distance V'Locity trains. They simply may not need the same power and acceleration of a current type, as they will typically do less stops per 100km, the tracks tend to be relatively flat, certainly for most of their distances. Conventional loco type trains may yet be an alternative in this situation.