I am looking at it from the realistic point of view of a switchman…not the “what if” point of view.
That and every idea I ever heard that started with “All you have to do is…” or "What if…"usually cost reams of money, never works, and are based on a single theory, excluding all other considerations…in this instance, all the other trains using the tracks…it isn’t like a freeway where your “short train” can just scoot over to the widget factory, drop off a few cars, grab the loads and hustle over to the local Wal Mart and drop them off…that’s exactly what LCL trucking companies are for, FedEx, UPS and such, who do have the option of city streets and picking their most efficient route.
There is an excellent reason for railroads doing away with single car service when ever they can, it doesn’t make money.
Where I work, we get the big 100 to 120 cars worth of general freight, which we switch out into blocks for our outlaying yards…where they are switched out into customer specific trains.
We combine those customer specific “small” trains into a single train, which works its assigned industries on a daily basis, in some instances, two or three times in a 24 hour period.
Several of theses train use our outlaying yards at the same time, which allows us to move 500,000 cars yearly.
The entire concept is based on the idea of forwarding every car you can in the next available train headed towards its final destination…dwell time in the yard cost the railroad money, and in spite of what you may imagine or heard, we do not let them sit for days if there is any way possible to move them.
Short trains would only gum up the works more; the physical plant has a finite capability in the number of trains it can accommodate, be they 12 cars or 120 cars long.
Now, if you playing in the “what if” world then sure, park the 120 car mixed trains and use your main line for dozens of 1