George,

Yes, taking the sulfur out and down to the various tiers of "clean diesel" has made a huge differnece. This is because refining out the sulfur, also reduces the aromatics, a source of secondary carbon particulate content, as well. This then allows for the more efficient fuel burn, and also for better NOx controls, due to less aromatic content (diesel gunk)to deal with.

Tier 4 is doable, and is being done with clean diesel and naturual gas, for almost all heavy duty prime mover applications. The issue increasingly for many industries and OEM's is: is it "worth" doing with diesel?

Based heavy duty truck and bus fleets will add significantly to their natural gas heavy duty fleets this year, and this year the number of heavy dutye natural gas fueling stations will nearly double, nationally. A number of fleet operators are talking to CNG providers about establishing a national "over the road" CNG filling station network, to allow for long distance heavy duty truck operatons on natural gas. I-40 is being proposed by some as the first such route.

The "tiered" diesel fuel standard is closely tied to the technology progress in "clean diesel" OEM (original engine manufacturer) technologies. This allows for the use of technologies to "cool and better control" the burn to reduce the NOx emissions, because there is less aromatic carbon and sulfur to deal with. However, the BTU equivalent cost per "gallon" of "clean" diesels can be over double triple the BTU equivalent cost of CNG, and those heavy duty CNG engines meet the same Tier 3 and 4 standards easily, at an equivalent, or in some cases lower long term/life cycle cost for the CNG engines.

Logistical and safety issues with CNG have resulted in fewer RR applications or demonstrations. These have been limited to a few experimental uses with yard engines. CNG is more difficult for RR's due to fuel density and storage issues on locomotives. But, it may be the long term significantly higher cost of diesel, especially the ultra-clean diesels required to meet these emission goals, that may begin to tilt the market to electrification of some major western RR corridors over the next decade, and justify the cost of capital involved. Thus far however, emissions reductions from cleaner fuels and tighter diesel emissions standards have been far more "cost effective" in dollars per ton of pollutant, than most electrification schemes I've seen.

Technology "forcing", through additional grant funds from the various "air pollution" reduction funding sources, is often used to assist in offsetting part of the higher cost of "cutting edge" low emission locomotive technologies at some of these commuter railroads. This is often less a game of politicians, as was asserted in an earlier comment, than the use of these kinds of fund sources to act as public "seed money" which is being used to "push" and subsidize the development and testing of the "next generation" emission technologies.

I was involved in providing funding for a number of these "technology forcing" programs involving locomotives, transit buses, and school buses, which required that in order to be eligible, you had to agree to use technology that achieved a standard "above and beyond" the adopted regulatory standards, and produce "surplus" emissions reductions to qualify. These innovations, now tested and viable, were then used and adopted as the next "tier" to be used in the next generation of OEM product lines, for the class of vehicles for which they were designed.

Corporations are neither good nor bad inherently. Like the people that created them, corporations run the gamet from responsible, civil, and moral providers of goods and services, to crooked, lying, and filching thieves, who would sell their own mothers under a street lamp for a buck. Many corporations, like most people, are not perfectly good nor perfectly evil. Most presented with new rules, new demands by society, or new demands of the marketplace, just try to figure out how to do what they need to do in the most cost effective way, while staying in business and trying to make a living, and morality per se, has little to do with that.

The bottom line is that we live in a world with air that's a lot cleaner than what we grew up with from a health perspective, and we are likely to continue to see real progress in doing more, at a lower cost per mile of operations, and with less fuel use per ton moved. And, that's not a bad Christmas present from this generation to the next.......

Merry Christmas to all, and to all a good night!

BOB2