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Meeting the Challenge

In the 15 years since Congress adopted the Clean Air Act Amendments (CAA) of 1990 , there have been dramatic improvements in diesel technologies. Starting in 2007,  new on-highway diesel engines now produce near-zero emissions thanks to cleaner fuels and advanced engine technologies. Similarly, the U.S. Environmental Protection Agency's Nonroad Diesel Rule will reduce nitrogen oxides (NOx) and particulate matter (PM) emissions from construction, agricultural and industrial diesel-powered equipment by 90% and 95%, respectively, compared to uncontrolled levels (pre-1996).

These clean diesel developments are key to achieving cleaner air in many of the nation's metropolitan areas, particularly considering EPA has recently announced more stringent federal standards – know as National Ambient Air Quality Standards (NAAQS) – for ozone and fine particulates.

While the environmental performance of diesel engines is constantly improving, new emissions standards only apply to new engines. However, because diesel is truly the workhorse of the American economy – with engines often lasting hundreds of thousands of miles or running for hundreds of thousands of hours – a sizable fleet of equipment manufactured over two to three decades ago can still be in operation. Fortunately, many of the same advances used to improve new engines can be applied to this existing fleet – providing cost-effective emissions reductions without compromising performance or fuel efficiency.

Diesel retrofits – broadly defined as replace, rebuild, refuel, retrofit and repower – offer a number of benefits over other emissions reduction strategies, including: cost effectiveness, immediate significant reductions, flexible and voluntary programs, and no new infrastructure requirements.

Cost Effectiveness

The Diesel Technology Forum compiled the data presented below to exemplify the cost effectiveness of various air quality improvement methods. This data was collected by the Metropolitan Washington (DC) Council of Governments and the Transportation Research Board from specific diesel retrofit projects. As shown in the graphic, diesel retrofit projects demonstrate significant cost-effective advantages as compared to other eligible CMAQ projects.

Similar figures were found by the National Research Council (N RC) in its assessment of the CMAQ program with the finding that “when compared on the sole criterion of emissions reduced per dollar spent, approaches aimed directly at emissions reductions…..have been more successful than most CMAQ strategies relying on changes in travel behavior.”

Recognition of diesel retrofits’ cost effectiveness led Congress to direct the Federal Highway Administration to give diesel retrofit projects priority for CMAQ funding in its 2005 reauthorization of the federal highway bill. In her introduction of the amendment that established this priority, Senator Hillary Clinton explicitly linked the development of the amendment to the findings of the NRC report and several members of Congress specifically cited the cost-effectiveness of diesel retrofit in reducing emissions as cause for their support of the amendment.

^{National Research Council, “The Congestion Mitigation & Air Quality Improvement Program: Assessing 10 Years of Experience – Special Report 264,”
(2002), pg. 9-10.}

Immediate Significant Reductions

In the past several years, major advances in diesel technologies have resulted in the development of cleaner diesel engines, fuels and retrofit devices that can be installed on vehicles and equipment to reduce in-use emissions by 25%-85%, depending on the technology and the characteristics of the vehicle or equipment.

In nearly all cases, the emission reductions are immediate. Planners don't need to wait to see if the reductions actually materialize by monitoring travel behavior – as can be required with many TCMs. Diesel retrofit strategies can be particularly important in metropolitan areas where high volumes of heavy-duty trucks are prevalent and/or where major construction projects are underway for long periods of time.

Flexible and Voluntary Programs

A number of voluntary approaches to diesel emission reductions have proved successful throughout the United States that, in contrast to regulatory measures, are less onerous and cumbersome than compliance with regulatory measures. The types of equipment and vehicles retrofit under these programs can include: heavy-duty trucks, forklifts, bucket loaders, tractors, wheel loaders, refuse trucks, transit and school buses and others.

Lack of Infrastructure Requirements

In contrast to many alternative fuel measures, diesel retrofit strategies do not require installation of special infrastructure. Ultra-low sulfur diesel fuel is now available nationwide. Another advantage to diesel retrofits is the ability to easily and quickly install technologies on diesel engines, equipment, and vehicles thereby minimizing vehicle downtime.

1. Data collected by government agencies overseeing specific diesel retrofit projects. Cost-effectiveness for each project depends on factors including: age and type of equipment being retrofit; off-road vs. on-road applications; Tier 0, 1, or 2 technologies; and other factors. Readers are encouraged to review source materials for assumptions.
   
   Examples cited are:
   
   Repower Lumber Loaders – South Coast Air Quality Management District project repowering 15 self-propelled lumber loaders (Los Angeles)
   
   Retrofit Transit Buses – Metropolitan Transportation Commission project retrofitting 1100 transit buses with Cleaire Longview ® (San Francisco Bay Area)
   
   Repower Off-Road Engines – California Air Resources Board project repowering off-road engines, such as graders and forklifts (nonattainment areas statewide)
   
   Repower Construction Equipment – South Coast Air Quality Management District project repowering 18 heavy-duty construction equipment engines (Los Angeles)
   
   Replace Older Trucks – Gateway Cities COG project replacing 250 pre-1983 heavy-duty diesel trucks with 1994 and newer trucks (southeast Los Angeles County)
   
   
2. Median cost-effectiveness estimate from the Transportation Research Board’s (TRB) 2002 study The Congestion Mitigation and Air Quality Improvement Program: Assessing 10 Years of Experience, page 341. Cost-effectiveness depends on numerous factors including participation levels, capital and operating costs, transit ridership, and other factors. See TRB report for methodologies and assumptions.
   
   
3. Cost-effectiveness calculations made by the Washington (DC) Council of Governments for specific projects. All projects shown in cost per ton of NOx using 2005 emissions factors. Details on projects include:
   
   Speed Limit Enforcement – 95 miles of enforcement in Northern Virginia
   
   Taxicab Replacement with CNG – Project replaced 100 cabs
   
   Bike Racks on Transit Buses – Bike racks on all buses
   
   Bus Replacement with CNG – Calculation made on 100 CNG buses