Years ago, I came up with a hybrid proposal that would help railroads during a period when only some lines were electrified. I ran the idea past a senior professor of electrical engineering (with a good knowledge of railroad technology) at a nearby University -- and he said there was no reason that the basic concept would not work.

The basic idea is this: For heavy freight trains, you have a consist of a six-axle diesel locomotive, a six (or four-) axle electric locomotive, and another six axle diesel locomotive.

Both the diesel and electric locomotives would need some modifications, though these diesels could come from existing inventories. The electric would probably have to be purpose-built with a heavier transformer and electrical gear than on standard electrics, but it could be based on existing technology.

The idea is this: Under wire, the electric locomotive not only powers its own traction motors but also feeds the traction motors on the diesels, which are in effect slugs. The electric locomotive also provides head-block heater power to the diesel prim movers, making them easier to start.

When you leave electrified territory, you start the diesel prime movers which also feed power to the traction motors on the middle electric unit, which now becomes a slug.

This type of setup would allow you to electrify a long base tunnel and some surrounding territory -- without having to change motive power at each end. Remember, base tunnels help eliminate steep grades, so this power combination could handle quite substantial trains.

-- Ernest