Talk of the pollution from electricity generation versus use on diesel trains is rather more complex than has been discussed so far.
With fossil fuels, you've got various different pollutants to consider.
From a diesel engine, due to the limitations of what can be done in the exhaust system, you will get even with a modern engine a fair amount of particulate matter- mainly unburnt fuel, residual sulphur compounds etc. This is a local pollutant, affecting only places nearby and is much more of a problem from road vehicles. Particulate pollution causing respiritory problems (astham etc) and can be carcinogenic.
Coal power stations (plus the rare oil and the modern biomass!) do produce particulate during burning, but with all the stations in the UK these days this is almost entirely scrubbed out of the exhaust using various methods, including electrostatic scrubbers in the flue. This does need disposed of however to landfill/reclamation (along with the furnace ash- Lognannet was built partly on reclaimed land made using the waste from Kincardine).
You've also got oxides of nitrogen from all combustive fuel burning (including gas) that are unavoidable due to the high combustion temperatures. Again, these are more readily removed at static power stations.
The one that gets headlines of course is CO
2. From a diesel engine, this will be mixed with much more harmful (both locally and as greenhouse gas) CO as well due to incomplete combustion. From a combustion power station, they are able again to deal with the CO in the flue.
Now, whether one or the other sourse produces more CO
2 per passenger km is more difficult, and I'll keep out of that area as I don't know enough.
But, of course, electric trains aren't tied to combustion. The Swiss, as said, use their plentiful Hyrdro power- not that hydro is 100% emission free- though emissions are very much "front loaded" for a new scheme. France generates nearly 80% of its electricity from nuclear. Wind, whilst having certain issues (no wind/too much wind), is growing very rapidly as the poster on the wall behind me shows. Tidal/wave will have a part to play. Spain now has some massive Solar power stations- these work well in very sunny locations, and are similar in the generation phase to a coal/gas/biomass/nuclear power station, except using mirrors to focus sunlight on to the boiler.
In fact, with a lot of these, the mention of other countires is perhaps key- really, power is something that needs considered more at European (and perhaps further) levels. There is a need for an intenrational, high efficiany "super grid" to balance out supply and demand, especially with talk of building vast solar farms in the north african desert.
yes, electric trains fail when the wires come down/there's a supply problem. But the motors on electric trains are much, much more reliable (witness the old Southern region practice of using old motors on new classes). They accelerate faster, produce less track wear and are generally more pleasent (if we're talking MUs, which realistically we are) for passengers.
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I'd say they could probably haul more aswell
Class 59 produces 2,460 kW (about the same as Deltic, as it happens). Class 92 is 5,040kW, Class 91 4,540kW.
OK, so then factor in gearing, but electric locos are able to be much more powerful. You notice it in MUs too- modern DMUs have all carriages powered, whilst EMUs have trailer cars (the class 317/320/321/322 have one motor car to three trailers), which contributes to the train being light.
