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State of New Jersey Department of Environmental Protection

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Environmental Regulation
Diesel Inspection and Maintenance

Notice of Rule Proposal
Control and Prohibition of Air Pollution from Diesel Powered Motor Vehicles: Motor Vehicle Inspection and Maintenance Program N.J.A.C. 7:27-14

Public Notice
Take notice that the NJ Department of Environmental Protection is proposing amendments to N.J.A.C. 7:27-14 – Control and Prohibition of Air Pollution from Diesel Powered Motor Vehicles: Motor Vehicle Inspection and Maintenance Program, to reduce the opacity cutpoints, strengthen the visible smoke standard for diesel-powered trucks and buses, and clarify the rules’ exemption for emergency vehicles.  This rulemaking is a part of the Department’s statewide effort to reduce diesel exhaust emissions from diesel-powered vehicles.  This proposal also represents a revision to the State Implementation Plan.

Diesel exhaust contains particulate matter in several size ranges, from coarse soot that can actually be seen as individual particles, to virtually invisible ultra-fine particles less than one micron in diameter (PM1.0).  In this proposal, the term "particulate matter" or "PM" means the mostly visible particle fraction, including particles up to 10 microns in diameter (PM10).  Although the opacity measurement technique utilized in the Diesel Powered Motor Vehicle Inspection and Maintenance Program (Diesel Inspection Program) focuses on PM10 emissions, reductions of particulate matter less than 2.5 microns in diameter (PM2.5, which is a fraction of PM10) will also occur when a vehicle is properly maintained.  Fine particle emissions from diesel engines can be reduced by implementing stricter diesel emission cutpoints and idling regulations, encouraging which encourages increased levels of maintenance and repairs.

Smoke opacity, which is an indicator of particulate matter, is the degree to which a plume of smoke will obstruct transmission of visible light.  It is typically expressed as a percentage of obstructed light.  When the Department adopted the existing smoke opacity cutpoints in 1998 (30 N.J.R. 901(a), 30 N.J.R. 2476(b)), excessively smoking diesel-powered vehicles were a common sight on the State's roads and highways.  Enforcement of the State's opacity cutpoints has made those excessively smoking vehicles the exception, rather than the rule.

Excessive smoke opacity is an established indicator of improper performance and poor maintenance.  Regular maintenance and common engine repairs help to control emissions of diesel exhaust particles and reduce other pollutants.  Reducing the opacity cutpoints for heavy-duty diesel vehicles and diesel buses will result in the reduction of visible quantities of particulate matter, including soot and air toxics throughout the State.

The proposed stricter cutpoints are based on an analysis of the periodic inspection records collected from 1998 through 2003.  The data indicate the fleet performs at smoke opacity emission levels significantly below the existing standard.  In developing the proposed cutpoints for a given engine model year, the Department took into account the average opacity value of those vehicles that passed the periodic inspection.  It then considered how often diesel engines of that model year achieved the same opacity value during inspection.  This data analysis indicated three opacity groups, very closely aligned with the level of engine control technology.  The propsed new opacity cutpoints are:

For trucks and other vehicles: 40% - 1990 and older; 30% - 1991 to 1996; 20% - 1997 and newer
For buses: 40% - 1987 and older; 30% - 1988 to 1993; 20% - 1994 and newer
For retrofitted buses: 30% - 1993 and older; 20% 1994 and newer.
All: no visible smoke of any color when the engine is at normal operating temperature.

As with the existing cutpoints, the older engines, controlled mechanically rather than electronically, would be subject to the least stringent cutpoint.  Newer electronically controlled engines, with various mechanical enhancements, would be subject to more stringent cutpoints.  The proposed stricter cutpoints are a natural continuation of the Department’s existing program.  No new test method, procedure or equipment is required.  In most cases, existing engines will be able to meet the proposed cutpoints by following the manufacturers’ recommended maintenance practices, or by repairing commonly occurring mechanical faults.

Although newer diesel-powered vehicles and equipment usually operate more cleanly and contribute less to air quality problems than their predecessors, diesel-powered trucks and buses tend to remain in service for 20 years or more.  Unless existing diesel-powered trucks and buses that operate in the State are properly maintained and repaired, such that the emissions from them are reduced, these trucks and buses will continue to contribute significantly to air pollution in the State for many years to come.

Since the Department is providing a 60-day comment period on this proposal, this proposal is excepted from the rulemaking calendar requirement pursuant to N.J.A.C. 1:30-3.3(a)5.

The proposal is scheduled to be published in the New Jersey Register dated June 16, 2008.  A copy of the proposal (PDF) is available from the Department’s website.  You can obtain an official copy of the proposal from LexisNexis Customer Service at (800) 223-1944 or    Be advised that there may be a fee for obtaining a copy of the proposal from some sources.

A public hearing(s) concerning the proposal is scheduled as follows:

Wednesday, July 30th, 2008 at 9:00 am
Department of Environmental Protection
Public Hearing Room
401 East State Street, Trenton, NJ 08625

Written comments may be submitted by August 15, 2008 (comment period extended to August 22, 2008) to:

NJ Department of Environmental Protection
Alice Previte
ATTN: 05-08-05/194
Office of Legal Affairs
PO Box 402
Trenton, New Jersey 08625

To open the PDF documents, you will need the Adobe Acrobat pdf reader to view. Left-click on the link and they will open. Or, right-click on the link and select "Save Target As" to save the document to your hard drive or personal directory. You can download the free pdf reader here.

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