Research Projects

Project at a Glance

Project Status: complete

Report Published April 1993:

Title: Technical feasibility of reducing NOx and particulate emissions from heavy-duty engines

Principal Investigator / Author(s): Browning, Louis

Contractor: Acurex Environmental Corporation

Contract Number: a132-085

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


Oxides of nitrogen (NOx) and particulate matter (PM) emissions from heavy-duty vehicles represent a significant portion of California's air quality problem. NOx, along with reactive organic gases (ROG), are responsible for the pervasive smog problems in most of California's urban areas. California contains two of the nine U.S. cities, Los Angeles and San Diego, which are in extreme ozone non-attainment. As for PM emissions, a recent body of research indicates health threats from this pollutant. The South Coast Air Basin (SoCAB) exceeds the current Federal annual average PM standard by 70 percent. Heavy-duty diesel engines account for a significant portion of the controllable, inhalable, directly-emitted PM emissions from on-road motor vehicles in the SoCAB. (It should be noted that diesel engines only account for about two percent of all PM emissions in the SoCAB). If California is to attain compliance with the National Ambient Air Quality Standards (NAAQS), established by the U.S. Environmental Protection Agency (EPA) as part of the Clean Air Act (CAA), reductions in these emissions are required.

Significant improvements in diesel engine technology and fuel control have made heavy-duty engines capable of meeting today's emissions standards. The current and future Federal and California emissions standards are listed in Table 2-l. In 1991, California reduced the PM emissions standard for buses to 0.1 g/bhp-hr. The federal standard for buses follows in 1993. During 1991 and 1992, only alternative-fueled and trap-equipped diesel production engines have been certified to meet the 1991 California Bus Standards. However, DDC has recently certified their Series 50 engine without aftertreatment which meets this standard.

Table 2-1. California and Federal Heavy-Duty Engine Emission Standards, U.S. FTP (g/bhp-hr)
1991 Federal-----5.0----0.25----5.0----0.25
1991 California--5.0----0.25----5.0----0.10
1993 Federal-----5.0----0.25----5.0----0.10
1994 Federal-----5.0----0.10----5.0----0.07
1994 California--5.0----0.10----5.0----0.07
1996 Federal-----5.0----0.10----5.0----0.05
1998 Federal-----4.0----0.10----4.0----0.05

In recognizing the heavy-duty vehicle emissions problem, the California Legislature adopted Senate Bills (SB) 135 and 2330. SB 135 (California Health & Safety Code (CH&SC) 43806) requires the Air Resources Board (ARB) to adopt emissions standards and test procedures applicable to new and replacement engines for urban transit buses by January 1, 1993. These standards are to be effective by January 1,1996, and will reflect the use of the best emissions control technologies expected to be available at that time. SB 2330 (CH&SC 43701) requires the ARB to consider adopting regulations that set low emissions standards for all heavy-duty vehicles. This report will be used in developing regulations for vehicles with a gross vehicle weight rating (GVWR) greater than 14,000 lb which will augment the interim transit bus regulations mandated by SB 135.

Before determining these new emissions standards, ARB has contracted Acurex Environmental Corporation to provide a technical feasibility assessment of current and future heavy-duty vehicle technology. The purpose of this assessment is to identify and evaluate heavy-duty engine technologies and/or combinations of technologies that can achieve low emissions. This includes evaluation of various emissions control techniques and their associated emissions reductions, performance effects, and costs.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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