I think that you can get good energy density with Hydrogen which will allow long train journey, but this will degrade further the overall efficiency as high compression of the gas is needed, and this energy is likely lost during usage.

Extremely good for weight and extremely poor for volume. To reduce the gasses volume storage is usually either highly compressed (200-700bar) or cryogenic (30K), like in the space shuttles tank.

In both cases the volumetric density is still quite poor, cryogenic is about 70g/l, which is actually less than the weight of hydrogen chemically bound in a liter of gasoline.

There exists some concepts of storing hydrogen chemically bound, e.g. to hydrocarbons or metal hydrites which release the gas on high temperatures (100-200°C).