Today’s invention is a way for people to board trains and disembark from them without the trains themselves ever slowing.
Having trains stop is pretty inefficient and it also means that the only place you can get aboard is at a station.
Instead, the idea is to have a small, electrically-driven micro-carriage running parallel to the train itself. People could get on this, via a simple siding, get up to speed, and when the two vehicles docked, simply walk from one to the other.
The accelerating engine would then disengage and run backwards to its siding, to wait for the next train and its passengers. Obviously this requires that the accelerative micro-carriages have efficient drive mechanisms and are monitored rigorously to avoid collisions. Some might stay docked, to allow for extra flexibility (A super clever system would have a range of microcarriages which would feed passengers from walking to bullet train speed).
In this way, main trains could avoid the problems of variable speed and passengers could board or get off at any one of a very large number of intermediate locations.