BOB2 Wrote:
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>
> In the late eighties, when I started working on
> diesel locomotive emissions, there were no
> regulations on diesel trucks or trains for
> emissions. The typical fleet average diesel
> emissions for nitrous oxides (NOx) from
> locomotives was over 40 grams per brake horsepower
> hour. This is why we had to cover our cars at
> Taylor yard at night back in the "good old' days.
> NOx would mix with fog from the LA River to create
> acids that would eat the paint on your car, or
> give you a nice face peel (you could feel it
> burning your skin), and we were breathing that all
> night.
>
> Included in that toxic locomotive emissions mix
> was a good dose of toxic diesel particulates, made
> up of a good deal of sulfur and carbon. And, I
> knew not just a few career rails who between
> smoking and this soot exposure had bad lungs.
>
> NOx is also a precursor chemical for Ozone, or
> good old fashion photo-chemical smog, it mixes
> with high octane hydrocarbons, and sunlight to
> cause Ozone. We used to refer to these then
> unregulated sources as "mobile NOx generators", as
> locomotives consisted then of a small but
> "untouchable" "Federal" source of emissions.
>
> New locomotives are now regulated for emissions
> and are now meeting tier 3 and 4 standards, with
> reductions in particulates, and over a 90%
> reduction in NOx. As a result of locomotive fleet
> replacement, over the last decade, this has made
> this a noticeably smaller source of air
> pollutants.
>
> Partial gas conversion at terminals and/or partial
> electrification of major western mountain
> corridors and mainlines might make long term
> economic sense, and also meet emission
> requirements at a lower cost. Cost and ROI on
> reasonable long term investment risk horizon will
> be the test of viability for all of these options.

Thanks BOB2 for your thoughtful description of diesel and natural gas propulsion and air quality issues.

Since 1989, I have been working for a transit authority. In 1988, the first federal regulations covering diesel emissions from transit buses were issued. Subsequently, the 1990 Clean Air Act Amendments had provisions with increasingly stringent requirements on diesel bus emissions. As with diesel locomotives, urban transit buses are much cleaner than they were 25 years ago.

I think that diesel-electric hybrid buses are the best choices for large transit systems as they are more energy efficient than straight diesels and quieter, too.

Although use of natural gas lowers particulate matter emissions, it is worse for NOx and generates more greenhouse gas emissions than diesel. However, there is a lot of pressure from the natural gas industry and politicians for us to convert to natural gas. I hope it doesn't happen.