Trains – October 2019

LOCOMOTIVE EMISSIONS control

is a major challenge for loco-

motive builders. Designing a

locomotive that meets increas-

ingly strict U.S. Environmental

Protection Agency emission

requirements while maintain-

ing horsepower, fuel efficiency,

and reliability has, no doubt,

kept many a design engineer

up at night. The standards,

implemented by regulation in

2000, have matured to the

existing Tier 4 standard on

Jan. 1, 2015. Two of the major

pollutants measured in a loco-

motive’s exhaust and regulated

by the EPA are nitrogen oxides

and particulate matter.

As emission-control stan-

dards ramped up, the builders

were able to accumulate emis-

sion credits. These were gener-

ated by using equipment on a

locomotive that would enable

it to save energy above and

beyond what such locomotives

could do without the added

equipment. For example, a

Tier 3-compliant SD70ACe

that had distributed power and

EMD’s Smart Consist system

installed and its use verified to

the EPA would be able to gen-

erate credits. This is because

equipment installed would re-

duce emissions while in ser-

vice. Earned credits could then

be applied to new locomotives

built to an earlier emission

standard, such as Tier 3, and

achieve the present-day Tier 4

16 OCTOBER 2019

LOCOMOTIVE

Emissions credits ride the rails

Program allows continued production of Tier 3 units

A Union Pacific credit ES44AC
is seen just west of Shawmut,
Ariz., on the Sunset Route. The
railroad has been acquiring
credit units since 2015. Chris Guss

A BNSF Railway credit unit’s builders plate shows such information

as the engine family it belongs to and what standards the locomotive

must be refurbished to at each major overhaul. Sean Graham-White