The problem with any electrification system is the method of supplying the power.
What are the relative benefits of overhead power vs third rails? Is there another method?
Should not this country consider Hydrogen Fuel Cells to power trains. They are cheaper and more reliable than Deisel or Electric trains systems.
Third rail power supply is not generally regarded as suitable for long distance mainlines.
The limited clearences mean that the voltage has to be quite low (less than 1,000 volts) this requires a much larger current to supply the power.
The combination of low voltage and high current means that substations have to be located at relativly frequent intervals which adds substantialy to costs for both equipment and land purchase.
Also the
HSE▸ are opposed to any significant expansion of the third rail network, they dont like the presence of a lethal voltage exposed at ankle height.
Fuel cells are very bulky and very expensive in sizes suitable for locomotive use, much bigger than a diesel engine.
Hydrogen fuel is also very bulky and problematic to store and handle, it must be stored either as a supercold liquid in a very expensive insulated tank, or as a gas under great pressure in special ultra high pressure tanks,
Refueling would be a complex operation, requiring sophisticated facilities, not like diesel fuel that simply needs a pump and a hose!
However the main objection to the use of hydrogen is that hydrogen is not a source of fuel, but a means of storing or transporting energy.
Hydrogen must be manufactured, there are two means of so doing on a large scale.
Firstly by the chemical treatment of natural gas, this is a well understood process, but natural gas suffers from the same problems of declining supply and rising prices as does oil. If natural gas is to be used, better to use it directly as liquified natural gas rather turn it into hydrogen.
Hydrogen can also by produced by electrolisis of water, this requires a great deal of power and there are already doubts as to the sufficiency of
UK▸ generating capacity. To electrify and use electricity directly would be more efficient.
Finaly having produced the hydrogen, it must be either compresed or liquified which requires considerable expensive plant, that also requires energy to run it.
Then convince the nimbys that it is safe to store hydrogen at rail depots etc! it is probably no more dangerous than petrol, but try convincing anyone of that. And it probably is more dangerous than diesel fuel.