Summary: Locomotives currently account for 22 percent of PM2.5 emissions and 17 percent of NOx emissions from all mobile sources, and their share of the emissions inventory will only grow as more stringent regulations for cars and trucks become effective. Meanwhile, switcher locomotives spend virtually all of their time within a rail yard, idling up to 75 percent of the time, often in close proximity to large urban populations.

M.J. Bradley's Advanced Vehicle Technology Group is currently managing an emissions reduction demonstration project on a commuter rail locomotive operated by the Massachusetts Bay Transportation Authority. Given their size and activity level, locomotives are a good target for emissions reduction programs, and can yield large, concentrated, and cost-effective emissions reductions. Apart from exhaust gas emissions control retrofits, idle reduction programs for switcher yard locomotives can provide substantial pollution reductions, with their cost-effectiveness enhanced by the fact that they also result in fuel savings. A number of factors contribute to providing substantial opportunities associated with locomotive emissions reductions.

The particulate matter (PM) emitted from a typical locomotive diesel engine in a year is equivalent to the annual PM emissions from as many as 75 highway trucks. Annual NOx emissions from five locomotives can equal the oxides of nitrogen (NOx) output of a 200 MW natural gas-fired power plant.

Locomotive emissions are so high for three reasons. First, locomotive engines are very large-with more than ten times the horsepower of even the largest highway truck. Second, locomotives get a lot of use-operating for 18 hours a day or more virtually every day of the year. Third, emissions regulations for locomotives have lagged behind rules for highway vehicles and other nonroad diesel sources by decades.

With the advent of more stringent regulation for cars and trucks, locomotives have come to account for a growing share of the emissions inventory. EPA estimates that without new controls, locomotive and marine sources together will account for 45 percent of PM2.5 and 27 percent of NOx emissions from all mobile sources by 2030.

Virtually all of the freight locomotives used in the U.S. are diesel-electric machines. The drive wheels are powered by electric motors, with the electricity produced on board by a large diesel engine coupled to a generator. Many passenger rail locomotives are pure electric machines, although some are diesel-electric.

Locomotives are remarkably durable, with a useful life of 40 years or more, even while accumulating up to 250,000 miles per year. Typically, the diesel engine is rebuilt every six to eight years.

Most of the nation's freight locomotives are used primarily in "line haul" service-moving large amounts of freight over long distances. On a national basis, long distance line haul operations account for about 73 percent of locomotive vehicle miles traveled, with an additional 15 percent from regional freight haulers. The line haul duty cycle includes a significant amount of time with the locomotive moving at high speeds and the engine operating at steady state.

By contrast, switcher locomotives spend virtually all of their time within a rail yard, assembling and disassembling trains. Switcher locomotives never reach high speeds and can spend up to 75 percent of their time idling. Overall, the switcher duty cycle is characterized by higher emissions than the line haul cycle.

Nationally, most locomotive emissions come from line haul freight operations, but switcher yards and commuter rail lines can be important local emissions sources, and are often located in closer proximity to urban populations. In some northeastern states over half of locomotive emissions come from passenger rail operations. An analysis of locomotive emissions at a large rail yard in Roseville, California, near Sacramento, showed that 50 percent of emissions came from trains moving through the yard, but that 45 percent came from idling locomotives.

EPA first regulated emissions from locomotive engines in 2000. In that year, a set of three standards (Tiers 0-2) became effective, with the operative standard depending on the year the engine was manufactured. Tier 0 standards apply retroactively to any engine manufactured between 1973 and 2001 when it is remanufactured. Tier 1 applies to new locomotive engines produced from 2002 to 2004; and Tier 2 applies to new locomotive engines produced beginning in 2005.

EPA's view is that the Tier 0-2 locomotive standards, unlike other diesel emissions standards, apply not only when the engine is first produced, but also every time the engine is remanufactured. This means that every locomotive engine built since 1973 must be upgraded to meet Tier 0 standards when it next has a major overhaul. Upgrading an unregulated locomotive engine to Tier 0 standards reduces NOx emissions by approximately 30 percent, although it produces no appreciable reduction in PM emissions. New engines built to comply with Tier 2 standards have approximately 60 percent lower NOx and 40 percent lower PM emissions than unregulated engines.

In June 2004, EPA issued an Advanced Notice of Proposed Rulemaking indicating that it was considering Tier 3/4 locomotive engine standards. These standards would be implemented for new locomotive engines built as early as model year 2011, and would seek to reduce both PM and NOx emissions by 90 percent or more compared to the Tier 2 standards. This would bring locomotive engine emissions roughly in line with emissions from onroad trucks and other nonroad engines for the first time.

While EPA has begun to implement emissions standards for new and remanufactured locomotives, it will be several years before these have a major effect. In the meantime, technologies exist that can be retrofit onto the current locomotive fleet during periodic engine remanufacture to give significant reductions of both NOx and PM in the short term. These include low-NOx injectors as well as improved pistons, cylinder liners, and piston rings.

In addition, the same types of "tailpipe" retrofit technologies that are currently being applied to onroad trucks and buses can be applied to locomotives. The two primary devices are diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs), both of which reduce PM emissions. DOCs can reduce total PM from a locomotive diesel by 20 to 50 percent, while DPFs (either passive or active) can give reductions of over 85 percent. Total annual PM emissions from a single locomotive can be reduced by 800 pounds or more with a DOC retrofit, while a DPF retrofit can achieve up to 2,000 pounds in annual reductions. Given their high baseline emissions and high usage, locomotives represent the most cost-effective applications for these retrofit technologies.

Space constraints may limit the use of both DOCs and DPFs on some locomotives, although this is less true for active DPF systems (which are more costly to operate since they incur a fuel penalty). DPFs will likely be required in order to meet EPA’s proposed Tier 3/4 locomotive engine standards. To date, there have been no applications of passive DPFs to locomotives. Both in Europe and in California there have been limited installations of an active DPF system made by HUG Engineering, mostly on switcher locomotives.

DOCs are more feasible than DPFs in the short term, and are applicable to virtually all locomotives-line haul, switcher, and commuter machines. M.J. Bradley's Advanced Vehicle Technology Group is currently managing the demonstration of an innovative DOC design on a commuter rail locomotive operated by the Massachusetts Bay Transportation Authority (MBTA) in Boston. So far, the device has been installed on one in-service locomotive and has also undergone emissions and durability testing at Southwest Research, in San Antonio, Texas. Although some technical hurdles remain, long-term plans include installation of this system on nine or ten of the MBTA’s commuter locomotives.

There is another key point here: the sulfur content of current locomotive diesel fuel (as high as 3,000 ppm) limits the use of PM retrofit technologies. Reducing fuel sulfur from 3,000 ppm to 500 ppm will by itself reduce PM mass emissions by as much as 20 percent, and will also allow retrofit with a DOC or an active DPF. Retrofit with a passive DPF requires even lower sulfur fuel content-no more than 50 ppm because the sulfur clogs up the filter.

EPA began to regulate the sulfur content of onroad diesel fuel in 1994, setting a limit of 500 parts per million (ppm). In order to allow the use of advanced catalytic emissions controls that will be required to meet future emissions standards for both onroad and nonroad diesel engines, the most recent EPA rules further reduce the allowable level of sulfur in onroad diesel fuel to 15 ppm beginning in late 2006, and control the sulfur level of nonroad diesel fuel for the first time. All nonroad diesel fuel will be limited to 500 ppm sulfur beginning in June 2007, and these limits will be reduced to 15 ppm for other nonroad equipment in 2010 and for locomotives and marine distillate fuels in 2012.

California has the authority to promulgate its own regulations for motor vehicle fuels under section 211(c) of the Clean Air Act, but California’s rules for locomotive fuels currently parallel EPA requirements. States other than California can regulate motor vehicle fuels only in limited circumstances. However, there is certainly no prohibition on the voluntary use of low-sulfur onroad diesel fuel by locomotives.

The DOC retrofit project at the MBTA was possible because the Authority uses onroad fuel in their locomotives, as is typical of many commuter rail operations. However, application of DOC technology to most freight rail operations will have to await the EPA-mandated reduction in nonroad diesel sulfur levels in late 2007.

The Argonne National Laboratory estimates that a typical switcher yard locomotive idles up to 75 percent of the time and that idling consumes 27 percent of its fuel. These locomotives are often allowed to idle for long periods to maintain engine oil and coolant temperatures, or to provide a relatively small amount of electrical power for auxiliary equipment. They may also be left to idle because the operator believes that it is easier to idle than to shut down and restart.

There are a number of alternative systems that can provide the necessary electrical power for auxiliary loads on locomotives. In addition, systems exist that monitor various engine parameters and automatically shut down the engine when idling is unnecessary, restarting it as required. According to EPA, these idle reduction systems cost between $4,000 and $35,000 to install on a locomotive, depending on the type of system. Given the amount of fuel that can be saved by reducing or eliminating idling, virtually all of these systems installed on a switcher locomotive have payback periods of six to 20 months, and can reduce annual PM emissions from a single locomotive by up to 100 pounds and annual NOx emissions by a ton. Commuter locomotives, and even some line haul locomotives, may also benefit from automatic shut-down/restart systems, though the emissions benefit will be less and the payback period longer.

At least one company also makes a hybrid-electric switcher locomotive called the "Green Goat." Rather than having a large diesel engine sized for peak load, this hybrid locomotive has a small diesel engine and a large battery pack. The batteries supply the peak power required for the locomotive to do its work, and the diesel continuously recharges them. This system eliminates all unproductive diesel engine idling, significantly reducing both fuel use and exhaust emissions. Because an onroad engine (subject to more stringent EPA emissions rules) can be used, the engine also has much lower per-gallon emissions of both PM and NOx than a traditional locomotive diesel. Although these hybrid locomotives are expensive, with a payback period based on fuel savings of over eight years, the price of a retrofit is competitive with a major engine overhaul and the technology may be an attractive alternative.

Another approach to reducing switcher locomotive emissions during remanufacture is conversion to a "gen-set" locomotive. The traditional locomotive engine and alternator are replaced with several large commercial diesel gen-sets, usually used for stationary power generation, that can produce equivalent electrical output. These diesel gen-sets are significantly cleaner than the locomotive engine they replace.

In June 2005 the California Air Resources Board (CARB) entered into a voluntary agreement with the state's two largest railroads, Union Pacific and BNSF Railway, to reduce pollution from California rail operations and to study and reduce the pollution from 17 identified California rail yards. CARB expects the agreement to reduce PM emissions from locomotives at and near rail yards by 20 percent. The two railroads agreed to take the following actions:

• Phase out all non-essential idling within six months and install idle reduction technologies on all California-based locomotives within three years.



• Implement annual smoke opacity testing of all locomotives that operate within California and commit to immediate repair of any locomotive with visible steady-state emissions exceeding 20 percent opacity. (This requirement is similar to that of opacity-based inspection and maintenance programs imposed on heavy-duty diesel highway trucks in 16 states.)



• Maximize the use of lower-sulfur onroad diesel fuel for locomotives in California, and ensure that as of January 2007 at least 80 percent of fuel supplied to locomotives in California meets EPA or California specifications for highway diesel fuel.



• Conduct health risk assessments at 17 California rail yards and use the results to identify risk reduction measures.

The agreement also has various reporting requirements for the railroads and includes penalties of up to $40,000 per month for violations.

CARB had previously signed a memorandum of understanding with railroads operating in the South Coast Air Basin (the Los Angeles area), which committed the railroads to a complete turn-over of the locomotive fleet within the air basin between 2005 and 2010. According to CARB, the prior agreement remains in effect and is unchanged by the new program.

CARB entered into these voluntary agreements because of its view of the preemptive effect of federal law on local regulation of locomotive emissions (more below). According to the agency, its approach will avoid a protracted fight over preemption and is the most effective way to reduce locomotive emissions.

Meanwhile, the South Coast Air Quality Management District (SCAQMD) departed from CARB's views on preemption, arguing that the recent agreement was weak and should not be implemented. SCAQMD claimed that virtually all of the provisions could have been adopted as regulations, with stricter requirements and stronger enforcement mechanisms.

In February 2006 SCAQMD took the next step, imposing stringent anti-idling rules and other requirements on locomotives operating in the region. The inevitable litigation followed a month thereafter, when the Association of American Railroads, Union Pacific, and BNSF Railway filed a lawsuit claiming that federal laws preempt the SCAQMD rules.

Although California has taken the lead with local regulation of locomotive idling, other states have begun to follow. For example, as part of a comprehensive rule to limit idling of all mobile source equipment, Rhode Island is contemplating limiting "unnecessary foreseeable" idling by diesel locomotives to no more than 30 minutes in any 60-minute period.

Section 209(e) of the Clean Air Act preempts state and local governments from adopting or enforcing "any standard or other requirement relating to the control of emissions from ... [n]ew locomotives or new engines used in locomotives." Although the Clean Air Act allows California to adopt its own rules for many other kinds of new mobile sources and permits other states to adopt the California rules instead of the federal requirements, that is not the case for new locomotives.

EPA interprets "new" to include "remanufactured" locomotives and locomotive engines, and has adopted regulations that prohibit state and local governments from enforcing any rules that would affect a locomotive manufacturer's or remanufacturer's design. EPA regulations specifically prohibit three categories of state and local controls for any locomotive for eight years after purchase or remanufacture: 1) emissions standards, 2) non-federal in-use testing programs, and 3) mandatory emissions control retrofit requirements.

However, section 209(e) provides:

Nothing in this part shall preclude or deny to any State or political subdivision thereof the right otherwise to control, regulate, or restrict the use, operation, or movement of registered or licensed motor vehicles.

Risky as predictions are, we side with the District on at least some aspects of the SCAQMD locomotive regulations and against all of the other notables-CARB, EPA and the railroads-arrayed on the other side of the preemption argument. At a minimum, it seems unlikely that federal law preempts strict anti-idling rules for switcher and even commuter locomotives. In any event, just as there is no prohibition on the voluntary use of low-sulfur onroad diesel fuel by locomotives, there is no bar to voluntary agreements whereby railroad companies adopt emissions reduction strategies.

A number of factors have converged to create opportunities associated with the reduction of locomotive emissions. First, emissions of PM2.5 and NOx from individual vehicles are extremely high. Second, emissions reductions from locomotives are highly cost-effective as compared to reductions from other mobile source categories. Third, although EPA has imposed some emissions standards on locomotives, available technologies and emissions reduction strategies make possible reductions deeper than those that are mandated, at least until the agency adopts more stringent standards. Fourth, some of the technologies are relatively new and have not yet penetrated the industry. And finally, the short payback period for many of the strategies opens the door to creative financing opportunities.

Locomotives are the next frontier in terms of emissions reduction opportunities. The annual PM emissions from a locomotive diesel engine can equal the annual PM emissions from 75 highway trucks. The annual NOx emissions from five locomotives are equivalent to the NOx output of a 200 MW natural gas-fired power plant. EPA estimates that without new controls, locomotive and marine sources together will account for 45 percent of PM2.5 and 27 percent of NOx emissions from all mobile sources by 2030.

Line haul locomotives, which transport freight long distances, are amenable to retrofit with diesel oxidation catalysts (DOCs), but switcher locomotives are particularly attractive candidates for both DOCs and idle reduction technologies. Switchers spend virtually all of their time within a rail yard (often close to dense urban populations), their duty cycle is characterized by relatively high emissions, and they can spend up to 75 percent of their time idling. In some cities, commuter locomotive fleets may also be important targets for both DOC and idle reduction technology retrofits.

Locomotives currently present a window of opportunity in terms of potential PM and NOx reductions. Apart from their high emissions and the relatively recent availability of retrofit and idle reduction technologies (with the result that the technologies have not yet penetrated the industry), emissions reductions from locomotives are highly cost-effective as compared to reductions from other mobile source categories. Environmental justice considerations and the new PM2.5 air quality standards make these reductions particularly attractive.

Although DOC retrofits will require grant funding, virtually all idle reduction technologies installed on switcher locomotives have payback periods of less than two years on account of associated fuel savings, with the result that low and no interest loans should also be effective financing mechanisms. The payback period for passenger locomotives may be somewhat longer than for switcher locomotives. However, especially in the densely settled northeastern corridor, publicly controlled passenger rail may present equally attractive retrofit opportunities despite their longer payback period.