Electrification maybe expensive, but, for high speed operations it is now being proposed to be installed on the Caltrain route and is part of the between Coalinga and Fresno (line to nowhere CAHSRA), and is proposed in the next phase of CAHSRA onward to just west of Bakersfield.

So we may see an interesting test of the actual (or extremely bloated????) costs, although this will be high speed electrification, with tensioning and design capable of 180 mph, (which we so far can't even manage to upgrade to in the NEC?)in the near future?

And, as to that evil "diesel" Metrolink which hauls 50,000+ riders per day, with folks of 30-40+ mile commutes is still less polluting, even with lousy (and more fuel efficient) Tier 3 loco's and Tier 4 HPU's, especially for CO2 emissions, than driving to work (and then there are the real transportation benefits in reducing competition for limited freeway space, and saving some of the enormous public and private costs of parking).

So the question is: what do you want to save the planet from? Is it localized ozone and diesel particulates, affecting public health now, or global warming gases, screwing over our great grand kids? You may find that you need a different control regime depending on what you are trying to achieve.

Tier 4, at least thus far, appears to be not yet a cost effective technology totally ready for prime time. And, maybe, if money grew on trees, and if we really took our environmental threats to our great grand children more seriously, then we probably would begin to electrify, yesterday.

The reality is that political and economic case for electrification won't very likely be made in the near term, with the kind of major changes in our tax laws and/or vast subsidies required to make such investments But, a "ton miles' equivalency, fleet averaging, or offsetting credits, with full availability of Tier 3 locos to replace the existing fleet is actually "doable", and thus, makes more sense from an environmental and public health standpoint, compared to the present course we appear to be on.