Commonwealth of Pennsylvania

Department of Environmental Protection

FINAL

State Implementation Plan Revision:

Diesel-Powered Motor Vehicle Idling Act

(Act 124 of 2008)

January 2010

Bureau of Air Quality

Pennsylvania Department of Environmental Protection

P.O. Box 8468

Harrisburg, PA 17105-8468

717-787-9495

www.depweb.state.pa.us

John Hanger

Secretary

Edward G. Rendell

Governor
(Blank for two sided copying)
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Pennsylvania State Implementation Plan Revision to Incorporate the DieselPowered Motor Vehicle Idling Act (Act 124 of 2008)

Purpose of Document

The purpose of this document is to request that the U.S. Environmental Protection Agency (EPA)

incorporate the Diesel-Powered Motor Vehicle Idling Act (Act 124 of 2008) into the 

Pennsylvania State Implementation Plan (SIP). The emission reductions achieved by imposing 

restrictions on the idling of diesel-powered motor vehicles with a gross weight (GW) equal to or 

greater than 10,001 pounds will allow the Commonwealth to make progress in attaining and 

maintaining National Ambient Air Quality Standards (NAAQS) including the health-based 

eight-hour ozone and fine particulate standards. 

If Act 124 is incorporated into the Pennsylvania SIP, it will become enforceable by EPA, in 

addition to continuing to be enforceable by state and local governmental entities. Pennsylvania 

will also be able to take credit in subsequent SIP revisions for emission reductions resulting from 

compliance with Act 124. 

Overview of Act 124

On October 9, 2008, Governor Rendell signed the Diesel-Powered Motor Vehicle Idling Act

(Act 124 of 2008; P.L.1511, No. 124); the law became effective on February 6, 2009. The act, 

codified at 35 P.S. §§ 4601- 4610, will reduce unnecessary idling of the main propulsion engine 

in diesel-powered motor vehicles, including trucks and buses. Act 124 prohibits the owners and 

drivers of any diesel-powered motor vehicle with a gross weight of 10,001 pounds or more,

engaged in commerce, from allowing or causing the engine of the vehicle to idle for more than 

five minutes in any continuous 60-minute period, except as provided in the act. In addition to 

vehicle drivers and owners, owners and operators of locations where subject vehicles load, 

unload or park are also responsible for compliance with Act 124.

Buses, school buses and school vehicles may idle for 15 minutes in a continuous 60-minute 

period when passengers are aboard. Other exemptions address excess idling due to factors 

outside the drivers’ control, such as traffic or mechanical issues. There are also exemptions 

addressing idling during maintenance, vehicle equipment inspection, and emergency or utility

service functions, and idling for security reasons. Certain types of other vehicles including 

motor homes, commercial implements of husbandry, implements of husbandry, farm equipment, 

and farm vehicles are not covered by Act 124. Additionally, the restriction on idling does not 

apply if a vehicle exhibits a label issued by the California Air Resources Board under 13 CCR 

§1956.8(a)(6)(C) showing the vehicle’s engine meets the optional nitrogen oxide (NOx) idling 

emission standard.

An owner or operator of a location where subject vehicles load or unload, or where 15 or more 

parking spaces are provided for vehicles subject to the act, must erect and maintain at least one 
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permanent sign to inform drivers that idling is restricted in Pennsylvania. The requirements of 

the law will not be incorporated into any permit issued by the Department of Environmental 

Protection (DEP). 

Any conviction for violations of Act 124 will result in fines ranging from $150 to $300, plus 

court costs. DEP is also authorized to assess civil penalties, not to exceed $1,000 per day for 

each violation of Act 124. Although Act 124 preempts and supersedes local anti-idling 

ordinances or rules, more stringent idling restrictions imposed by counties of the first and second 

class (Allegheny and Philadelphia counties) prior to Jan. 1, 2007, continue in full force and effect 

provided they are not amended, suspended or rendered invalid. See Appendix A of this 

document for a copy of the law. 

Benefits of Act 124

Act 124, which requires idling reduction by diesel-powered vehicles over 10,000 pounds gross 

weight, will help reduce emissions of pollutants that contribute to ground-level ozone and fine 

particulate matter concentrations. Projected emission reductions, assuming at least a 50% 

compliance rate, are shown below in Table 1 for volatile organic compounds (VOC), nitrogen 

oxides (NOx) and fine particulate matter (PM2.5).

Table 1: Projected Emission Reductions from Act 124

(tons per year)

2009 2018

VOC 45 30

NOx 1622 1600

PM2.5 30 7

In 1997, the EPA established ozone and PM2.5 primary and secondary NAAQS to be more 

protective of public health and the environment than earlier ozone and particulate matter

standards and to ensure an adequate margin of safety. In October 2006, EPA further tightened 

the 24-hour PM2.5 standard, and in March 2008, EPA strengthened the ground-level ozone 

standards. In September 2009, EPA announced that it will reconsider the 2008 ozone standard in 

order to ensure the standard is clearly grounded in science, protects public health with an 

adequate margin of safety, and is sufficient to protect the environment. 

Fine particles or PM2.5 (particles with a diameter of 2.5 micrometers or less) in the atmosphere 

are made up of a complex mixture of components. Some, like diesel particulate, are emitted 

directly into the air (primary sources) and others, such as sulfate and nitrate, form in the air as a 

result of various chemical reactions (secondary sources). The health effects associated with 

exposure to PM2.5 are significant, and the evidence for these effects is compelling. Premature 

mortality, aggravation of existing respiratory and cardiovascular disease, decreased lung function 

and asthma attacks have been attributed to exposure to PM2.5.

Ground-level ozone is not emitted directly to the atmosphere but is formed by a photochemical 

reaction between VOCs and NOx in the presence of sunlight. Heavy-duty vehicles contributed 
Incorporation of Act 124: SIP Revision

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about 25% of all NOx emissions in this Commonwealth in 2002. (Compared to gasolinepowered vehicles, diesel vehicles are not a significant source of VOCs.) Repeated exposure to 

ozone pollution may cause a variety of adverse health effects for healthy people and those with 

existing conditions, including difficulty in breathing, chest pains, coughing, nausea, throat 

irritation and congestion. It can exacerbate bronchitis, heart disease, emphysema, and reduce 

lung capacity. Ozone can aggravate asthma, causing more asthma attacks, increased use of 

medication, more medical treatment and more frequent visits to hospital emergency clinics. 

Ozone also has adverse effects on vegetation (forests and food crops) and, through deposition of 

NOx precursors, contributes to pollution in the Chesapeake Bay.

Furthermore, EPA and other agencies have evaluated the health effects of direct exposure to 

diesel particulate matter. The small size of diesel exhaust particles allows them to be drawn 

deeply into the lungs. Diesel particulates are, for the most part, even smaller than 2.5 

micrometers. The EPA has said that long-term exposure to diesel particulate exhaust is likely to 

pose a lung cancer hazard. Exposure to diesel particulates has non-cancer and acute effects as 

well, including throat and eye irritation and inflammation, exacerbation of existing respiratory

and allergic conditions, and exacerbated risk of heart attacks. Studies indicate that children 

living near highways have more lung and breathing problems than other children. Children may

also be exposed to more diesel exhaust inside diesel school buses, especially in idling buses that 

queue. People commuting to work in almost any mode of transportation along truck routes are 

exposed to high levels of diesel fine particulate matter.

Vehicle operators, the people in the closest proximity to diesel exhaust, will benefit most, 

particularly drivers of long-haul vehicles. In addition to cleaner air, the noise of their sleeper 

berth should decrease if power is supplied by an alternative power source. This should lead to a 

more rested truck driver. The National Transportation Safety Board has cited fatigue as a major 

cause of accidents in which long-haul trucks are involved. Nearly 500,000 trucks in the nation 

are dedicated to long-haul trips. Since trucking companies need to replace truck drivers 

constantly due to high turnover rates, more truck operators would be affected than there are 

number of trucks. It is possible that most, if not all, long-haul drivers will idle in this 

Commonwealth at some time. Including bus drivers and local drivers in this Commonwealth, 

there are nearly one million drivers who may benefit through reduced exposure to diesel 

emissions.

In addition, because idling heavy-duty vehicles consume approximately one gallon of fuel per 

hour, reducing idling will save diesel vehicle owners and operators money over the long run. 

Because the United States increasingly relies on imported fuel for transportation needs, reducing 

idling will contribute to the country's energy independence. Another benefit of reducing idling is 

the reduction of carbon dioxide (CO2) emissions, a major greenhouse gas. Idling heavy-duty 

diesel vehicles can produce as much as 22.2 pounds of CO2 for every hour of idling time. 

Public Comment

Requirements for a public comment process are set forth in Section 110(a)(2) of the CAA and 40 

CFR Section 51.102(d). Public hearings on the incorporation of Act 124 into the Pennsylvania 
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SIP were held in Harrisburg on September 17, 2009, and in Norristown and Pittsburgh on

September 18, 2009. Notice of the hearings was published in the Pennsylvania Bulletin on 

August 15, 2009, and in newspapers in general circulation at least 30 days prior to the date of the 

hearing. The public comment period ended on Friday, September 25, 2009. A 

comment/response document has been developed and is being submitted to EPA with this final 

SIP revision. 
Appendix A

ACT 124

Diesel-Powered Motor Vehicle Idling Act

(P.L. 1511, No. 124)