COMMENTS ON PROPOSED INTERIM MOTOR VEHICLE 

EMISSIONS BUDGETS FOR SOUTH COAST AIR BASIN 

Prepared by

Robert E. Yuhnke 

Adrian Martinez 

And

Michael Replogle 

 The Coalition for Clean Air, Coalition for a Safe Environment, Endangered Habitats 

League, Environmental Defense Fund, East Yard Communities for Environmental Justice, Coalition 

for a Safe Environment, and the Natural Resources Defense Council submit these comments on the 

proposal by the California Air Resources Board (“CARB”) to adopt motor vehicle emissions 

budgets (MVEBs) as part of the Air Quality Management Plans (AQMP) for Ozone and PM2.5 that 

have been submitted to EPA as part of the State Implementation Plan (SIP) for the South Coast Air 

Basin (“SCAB”). The proposed budgets are currently under consideration by EPA to determine if 

they meet the criteria for an adequate budget that can be used for conformity purposes prior to 

EPA’s approval of the attainment demonstration and implementing measures. For the reasons 

described below, the proposed interim budgets for PM2.5 do not meet the federal requirements for 

adequacy and should not be approved by EPA until California submits a complete attainment 

demonstration for all portions of the SCAB and adopts additional measures as needed to achieve the 

emission reductions required by the Clean Air Act (“CAA” or “Act”) to achieve reasonable further 

progress (“RFP”) prior to the attainment deadline, and to attain the National Ambient Air Quality 

Standards (“NAAQS”) by the attainment deadline. 

Executive Summary. 

 Commenters object to EPA’s approval of the submitted interim budgets for PM2.5 based on 

two broad concerns:

I) The failure of the attainment demonstration to – 

A) Identify the elevated concentrations of PM2.5 in the near-highway environment that have 

been shown by numerous studies to significantly exceed concentrations recorded at regional 

monitors, and

B) Estimate the emissions reductions needed to attain the NAAQS in the near-highway 

environment and include a control strategy designed to reduce these elevated near-highway 

concentrations to the level of the NAAQS; and 

II) The reliance in the AQMP on measures that may not be implemented in the relevant 

horizon year (or at all), for the purpose of demonstrating attainment and RFP, including but not 

limited to, emissions reductions expected from the marine vessel fuel rule recently set aside by the 

United States Court of Appeal for the Ninth Circuit, emissions reductions attributed to EPA’s 

locomotive rule which are not projected to be achieved by 2014, and emission reductions from non-
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road engines assumed in the AQMP, but that may not be mandatory. Further, CARB has failed to 

include several strategies aimed at reducing rail emissions. 

 Until the emissions reductions needed to attain the annual and 24-hour NAAQS for PM2.5 

in the near-highway environment are known, the emissions reductions needed to meet the RFP 

targets in the milestone years cannot be determined. Unlike ozone, where the RFP targets require a 

fixed annual reduction in emissions at the rate of 3% of the baseline emissions inventory, the RFP 

targets for PM2.5 are based on the annual reductions needed to achieve the overall reduction target 

required for attainment. The adopted AQMP contains emission reductions that will achieve the 

regional reductions shown by the modeling to be necessary for attainment at monitors that do not 

reflect the incremental impact of highway emissions in the near-highway environment. The 

attainment demonstration in the AQMP fails to estimate the reductions in primary particulate 

emissions from highways needed to attain in the near-highway environment where approximately 

1.5 million citizens in the SCAB within 300 meters of major freeways carrying more than 125,000 

vehicles a day will be exposed daily to continuing NAAQS violations. The RFP targets that will be 

needed to attain the NAAQS in all communities in the Basin cannot be determined from the adopted 

AQMP. All that can be said is that the overall reductions in the adopted AQMP are not sufficient to 

eliminate the NAAQS violations in the near-highway environment, and therefore the RFP targets 

based on that plan cannot be adequate to achieve the percentage reductions that will be needed for 

an adequate attainment demonstration. For this reason, the proposed emissions budgets cannot be 

adequate for conformity purposes, and do not meet EPA’s requirements for adequate emission 

budgets. 40 CFR § 93.118(e)(4). 

 In addition, EPA requires that emissions budgets be based upon emissions reductions that 

can be expected from adopted measures. 40 CFR § 93.118(e)(4)(v). The proposed budgets for both 

ozone and PM2.5 are based, in part, on emission reductions expected from measures identified in 

the AQMP that may not be achieved, and will not be achieved because they are not based on any 

currently adopted, legally enforceable obligation. 

 Until an attainment demonstration for PM2.5 is adopted that provides for attainment in the 

near-highway environment, and the measures needed to achieve the reductions required to attain are 

identified, it is premature to establish any emission budgets for PM2.5 emissions from motor 

vehicles. In addition, until the measures needed to achieve reasonable further progress for ozone are 

adopted, proposed RFP budgets for ozone cannot be adequate. We therefore ask EPA to postpone 

action on the submitted interim budgets until these deficiencies in the AQMP are remedied. 

I. MOTOR VEHICLE EMISSION BUDGETS MUST BE ADEQUATE TO 

PROVIDE FOR ATTAINMENT AND REASONABLE FURTHER 

PROGRESS.

To satisfy the Act’s conformity requirements (id., §7606(c)), the SIP, including its MVEB, 

must ensure that “emissions expected from the implementation of [transportation] plans and 

programs are consistent with ... necessary emissions reductions” from the SIP. Id., §7506(c)(2)(A). 

EPA has interpreted the necessary emission reductions to be those reductions needed to attain the 

NAAQS and the interim emission reduction milestones required for RFP. EPA’s conformity rule 
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requires that “when considered together with all other emissions sources, [the MVEB must be] 

consistent with applicable requirements for . . . attainment” and be “consistent with and clearly 

related to the emissions inventory and control measures” in the SIP. 40 C.F.R. Part 93.118(e)(4)(ivv). The adopted AQMP is facially inadequate, admitting insufficient control measures to 

accomplish the daily emissions reductions necessary to attain the PM2.5 and ozone standards.

These shortfalls are relevant to the adequacy of the MVEBs, since motor vehicles are the largest 

single source of ozone precursors and the primary emitter of elemental carbon, one of the 6 critical 

species of PM2.5 in the South Coast air Basin. 

EPA defines and describes the role of MVEBs in the SIP as follows: 

“Motor Vehicle Emissions Budget is that portion of the total allowable emissions defined in 

the [SIP] ... for the purpose of ... demonstrating attainment ... of the NAAQS ... allocated 

to highway and transit vehicle use and emissions.” 40 C.F.R. Part 93.101. 

“Motor vehicle emissions budgets are the . . . motor vehicle-related portions of the 

projected emissions inventory used to demonstrate . . . attainment . . . for a particular year 

specified in the SIP. The motor vehicle emissions budget establishes a cap on emissions 

which cannot be exceeded by predicted highway and transit vehicle emissions.” 58 Fed. 

Reg. 62,194 (November 24, 1993). 

The MVEBs adopted in the SIP for a nonattainment area are implemented through the 

transportation planning process by the adoption of a long range Regional Transportation Plan 

(“RTP”) and short range Transportation Improvement Program (“TIP”) that “shall implement the 

transportation provisions of any [SIP] applicable to all or part of the area covered by such 

transportation plan or program.” 42 U.S.C. §7506(c)(2). The RTP defines the future regional 

transportation system envisioned for a 20-year horizon, and the TIP prioritizes the projects to be 

funded in the next three years. 23 U.S.C. §134(g), (h). The RTP and TIP are required to be adopted 

by the metropolitan planning organization (“MPO”). Id. To ensure that the RTP and TIP do not 

cause emissions that exceed the MVEBs, “[n]o [MPO] shall give its approval to any project, 

program or plan which does not conform to an implementation plan approved or promulgated under 

section 7410 of this title.” 42 U.S.C. §7506(c)(1). Further, “no [RTP or TIP] may be adopted by a 

metropolitan planning organization ... until a final determination has been made that such plans and 

programs are consistent with the estimates of emissions from motor vehicle and necessary 

emissions reductions contained in the applicable implementation plan”. Id.

§7506(c)(2)(A)(emphasis added). Conforming to a SIP requires a determination that RTPs, TIPs 

and projects conform to a SIP’s purpose of expeditious attainment of the ambient air quality 

standards, §7506(c)(1)(A), and that such transportation plans, programs and projects will not: 

(i) cause or contribute to any new violation of any standard in any area; 

(ii) increase the frequency or severity of any existing violation of any standard in any area; 

or

(iii) delay timely attainment of any standard or any required interim emission reductions or 

other milestone in any area. Id., §7506(c)(1)(B).
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In addition to establishing obligations that the MPO must satisfy, the Act also requires that 

“[n]o federal agency may approve, accept or fund any transportation plan, program or project unless 

such plan, program or project has been found to conform to any applicable implementation plan in 

effect under this chapter.” Id., §7506(c)(2). The U.S. Department of Transportation (“US DOT”) 

may not “approve[], accept[] or fund[]” a project unless it comes from a conforming regional plan 

and TIP. Id., §7506(c)(2)(C).

MVEBs thus set limits on motor vehicle emissions that must be achieved by the RTP and 

TIP adopted by the regional transportation agencies and approved by US DOT. If the MVEBs are 

set too high and transportation projects are constructed that, through their design, generate more air 

pollution than is consistent with expeditious attainment of the ambient air quality standard, the 

Act’s conformity requirements are thwarted. 

A. MVEBs From SIPs That Do Not Attain Must be Disapproved. 

The Ninth Circuit Court of Appeals has consistently held that a SIP that fails to require 

emissions reductions needed for attainment may not be approved. Delaney v. EPA, 898 F.2d 998 

(9th Cir.), cert.denied, 111 S.Ct. 556 (1990), Arizona v. Thomas, 294 F.2d 834 (9th Cir. 1987), Hall 

v. EPA, 263 F.3d at 937. Concluding that the basic criteria for SIP review adopted by the Supreme 

Court in 1975 continue to apply to the 1990 Amendments, this Court recently reiterated that “[t]he 

objective of the EPA's analysis is to determine whether ‘the ultimate effect of a State's choice of 

emission limitations is compliance with [NAAQS].’ Train, 421 U.S. at 79.” Hall v. EPA, 263 F.3d 

at 937. “EPA must determine the extent of pollution reductions that are required and determine 

whether the emissions reductions effected by the proposed revisions will be adequate to the task.” 

Id., at 938. If the emission limitations are not sufficient to attain, “the EPA should disapprove a plan 

revision if ‘the plan as so revised would no longer insure timely attainment of the national 

standards.’ Id. at 90. See also id. at 93 (stating that a revision would be disapproved if it ‘caused a 

plan to fail to insure maintenance of those standards’).” Id., 936.

Here, EPA’s obligation is to disapprove the attainment demonstration in the submitted 

PM2.5 SIP for the SCAB because the demonstration fails to assess the reductions of primary PM2.5 

emissions from highways that are needed to demonstrate attainment in the near-highway 

environment, and fails to include control measures needed for attainment. The control measures 

needed for some of the emissions reductions have not been identified, adopted or submitted to EPA. 

A fortiori, the MVEB from this SIP also fails to provide for attainment because the allowed motor 

vehicle emissions, when considered together with other measures in the SIP, do not provide for 

attainment. A MVEB that does not provide for attainment, does not provide the “necessary 

emissions reductions” required by §7506(c)(2)(A), or the emissions reductions necessary to ensure 

that the transportation plan and program for the region “will not cause or contribute to any new 

violation, [or] delay timely attainment” as required by §7506(c)(1)(B)(iii). Accordingly, such 

budgets may not be approved as a partial SIP under the Act, or found adequate for transportation 

conformity purposes under EPA’s conformity rule. 
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There is no dispute that the AQMP does not contain enough enforceable control measures or 

even identified and committed measures to provide for attainment of either the PM2.5 or ozone 

NAAQS as required by section 7502(c)(1) and (6) and EPA rules governing the requirements for an 

approvable SIP.1

Indeed, the SIP does not even identify proposed or candidate control measures that might be 

conditionally approved under section 7410(k)(4). The ARB has identified some measures to be 

considered for adoption to achieve the overall reductions identified in the attainment demonstration, 

ARB Resolution 07-28, Attachment B, but these measures do not include commitments to achieve 

specific reductions within the 1 year period allowed by the CAA. Under these facts where the State 

acknowledges that the SIP does not contain adopted measures that provide for attainment, and 

where the evidence shows that the attainment demonstration itself is not adequate, it is unlawful to 

nonetheless approve that part of the SIP that will be used to determine the maximum allowable 

emissions from the regional transportation system for the next 20 years. EPA cannot approve the 

submitted budgets because “the EPA's analysis [cannot] ‘rationally connect[]’ its approval of 

particular plan revisions before it to its assessment of an area's prospects for meeting current 

attainment requirements.” Hall, 263 F.3d at 939. Without further emissions reductions, EPA’s 

approval of the MVEBs in the submitted plan gives the regional transportation planning agencies a 

green light to use inflated emissions budgets for the design of the future regional transportation 

system and in approving TIPs and transportation projects. EPA may not make lawful a level of 

emissions from the transportation system that will perpetuate existing nonattainment. 

This result is expressly prohibited by the conformity rule EPA promulgated in 1997 to 

govern the determination whether MVEBs in a SIP may be found adequate for the purpose of 

implementing the conformity requirements of §7506(c): 

EPA will not find a motor vehicle emissions budget in a submitted control strategy 

implementation plan revision ... to be adequate for transportation conformity purposes 

unless ... : (iv) the motor vehicle emissions budget(s), when considered together with all 

other emissions sources, is consistent with applicable requirements for ... attainment... 40 

C.F.R. Part 93.118(e)(4). 

In the preamble to its conformity rule, EPA explained that this rule required MVEBs to be part of a 

SIP that provides for attainment. “When considered with point, area and mobile sources, the 

emissions budget(s) must be consistent with applicable requirements for ... attainment.” 62 Fed. 

Reg. 43,781 (Aug. 15, 1997). In that rulemaking, EPA expressly rejected arguments that MVEBs in 

SIP submittals that failed to include emissions reductions sufficient to provide for attainment should 

nonetheless be allowed to be used for RTP and TIP conformity determinations until adequate 

emissions control measures were submitted by the State: 

1

 “Each plan must demonstrate that the measures, rules, and regulations contained in it are adequate to provide for the 

timely attainment and maintenance of the national standard that it implements.” 40 C.F.R. Part 51.112(a). 
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[I]f a SIP does not identify enough emissions reductions and the motor vehicle budget does 

not provide for ... attainment, then there is no basis to claim that a transportation activity 

conforms. 

 * * * 

EPA believes it is not possible to find new projects to conform if the SIP does not identify 

enough emissions reductions and the motor vehicle budget does not provide for ... 

attainment. Clean Air Act section 176(c)[(1)(B)(i)-(iii)] requires that projects must not 

worsen violations or delay attainment, and there is no basis to make this claim if the SIP has 

been disapproved. Additional transportation projects may worsen existing violations.

Transportation Conformity Rule Amendments, EPA Response to Comments Document, at 34, 35 

(June 23, 1997) (emphasis added).EPA expressly interpreted §7506(c) and Part 93.118(e)(4)(iv) to 

bar the use of budgets to determine the conformity of new transportation projects when the SIP does 

not contain sufficient emissions reductions to provide for attainment. 

In its review of EPA’s conformity rule, the U.S. Court of Appeals for the District of 

Columbia also interpreted the Act to bar use of a MVEB for conformity purposes if the SIP from 

which it came failed to require enough emissions reductions to provide for attainment. EDF v. EPA,

167 F.3d 641, 650 (D.C. Cir. 1999). EPA originally adopted a rule allowing submitted budgets to be 

used for transportation conformity purposes without any EPA review or approval of the SIP. The 

D.C. Circuit rejected the use of submitted budgets by transportation agencies for making conformity 

determinations before EPA found them adequate precisely because there was no basis for 

determining that RTPs and TIPs designed to meet the emissions levels in submitted budgets would 

satisfy the three statutory conformity criteria contained in §7506(c)(1)(B)(i)-(iii). As the Court 

explained, when EPA failed to: 

determin[e] that [the SIP revision] contains adequate measures to reduce emissions to 

statutorily required levels, ... there is no reason to believe that transportation plans and 

programs conforming to the submitted budgets “will not—(i) cause or contribute to any new 

violation of any standard in any area; (ii) increase the frequency or severity of any existing 

violation of any standard in any area; or (iii) delay timely attainment of any standard.... 42 

U.S.C. §7506(c)(1)(B). EDF v. EPA, 167 F.3d at 650. 

If a rule that allowed conformity determinations to be based on submitted budgets in SIPs is 

inconsistent with §7506(c) because EPA had not yet determined that the SIP provided sufficient 

emissions reductions to attain, then, a fortiori, a MVEB must not be lawful for conformity purposes 

where the State has affirmatively acknowledged that the SIP does NOT reduce emissions to the 

levels required for attainment. EPA would need to perpetuate the unlawful policy struck down by 

the D.C. Circuit in order to find adequate the MVEBs from a SIP that does not contain the 

emissions reductions needed for attainment, or for RFP. If EPA concludes that the SIP fails to 

contain sufficient emissions reductions for attainment or RFP, the legal result must be the same as 

when EPA had made no findings at all: there is no basis for determining that transportation plans 

and programs conforming to the submitted budgets will not violate the statutory criteria for 

conformity. 
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 Here the State seeks to circumvent these limitations on EPA’s ability to approve the 

submitted budgets by relying on the measures listed in ARB Resolution 07-28 Attachment B. But 

these measures are proposed for consideration, are not committed to be adopted within the 1 year 

period allowed by § 7410(k)(4) of the Clean Air Act, and are not committed to achieve specific 

emission reductions. EPA may not lawfully rely on this Resolution to conditionally approve the 

AQMP pursuant to § 7410(k)(4).

B. EPA Action on the MVEBs Requires Notice and Comment. 

It is well-settled that EPA action on a SIP revision is governed by notice and comment 

procedures required by the APA. “The APA requires an agency to: (1) publish a general notice of 

proposed rulemaking; (2) give interested parties an opportunity to participate in the rulemaking 

through submission of data, views, and arguments; and (3) adopt a rule after consideration of the 

relevant matter presented.” Hall v. EPA, 263 F.3d at 941, citing Ober v. EPA, 84 F.3d at 312. 

EPA cannot act to give legal effect to the submitted MVEBs without first publishing notice 

of proposed rulemaking and providing an opportunity for public comment in response to a proposed 

action. Here, EPA has merely posted a notice on a website stating that the SIP had been received. 

No specific action has been proposed. Public comment cannot focus on a proposed action.

EPA’s determination of the adequacy of a MVEB as part of the SIP would be final agency 

action because it would establish obligations with legal consequences. Bennett v. Spear, 520 U.S. 

154, 177-78 (1997). EPA’s decision determines the rights of the public in the implementation of one 

of the most critical part of the Basin’s air pollution control strategy, and the duties of the region’s 

transportation agencies to implement that strategy. 42 U.S.C. §7506(c)(2). Once the MVEBs are 

found adequate by EPA, they become the limits on motor vehicle emissions that must be met as the 

condition required for adoption and approval of transportation plans, programs and projects. 40 

C.F.R. Part 93.118(e)(1).2

 “In order for each transportation plan, program and FHWA/FTA project 

to be found to conform, the MPO and DOT must demonstrate that the applicable criteria and 

procedures in this subpart are satisfied....” 40 C.F.R. Part 93.109(a). The finding of conformity 

includes a demonstration that motor vehicle emissions will be equal to or less than the approved 

MVEB. 40 C.F.R. Part 93.118(a). Thus the MVEBs impose important legal obligations on 

transportation agencies that must be satisfied before transportation plans and programs may be 

approved. Individual transportation projects may not be approved or funded unless they come from 

a currently conforming plan and TIP. 42 U.S.C. §7506(c)(2)(C); EDF v. EPA, 167 F.3d at 645-650. 

Once approved, the MVEBs in the South Coast SIP establish requirements that must be satisfied as 

a condition for the allocation and expenditure of billions in federal and state transportation funds 

annually.

2

 Although commenters disagree that action on a budget may preclude effective judicial relief, EPA contends that once 

an RTP, TIP or project has been found to conform on a MVEB adequate at the time, the finding cannot be subsequently 

cancelled. 40 CFR § 93.118(e)(3). Not only is EPA’s MVEB adequacy determination binding on transportation 

agencies, the determination is allegedly irreversible thereby making it binding on the Courts and precluding judicial 

reversal of an unlawful action after judicial review. This unquestionably defines the adequacy determination as final 

agency action escalating the APA significance of the adequacy determination. 
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EPA cannot lawfully give legal effect to the submitted budgets without first publishing a 

notice of proposed rulemaking with a statement of basis and purpose that would apprise interested 

parties of the action the Agency intends to take and the reasons supporting the action. To date, 

interested parties have been given no notice of whether EPA considers the SIP and attainment 

demonstration approvable under section 110, and why the submitted MVEBs are approvable as part 

of the attainment SIP. Nor has the Agency identified the criteria that are applicable and relevant for 

making that determination. Without some notice of the Agency’s intention and the reasons 

supporting the proposal, commenters are being denied the procedures guaranteed by the APA that 

protect our opportunity to submit meaningful comments relevant to the basis for Agency action. 

Commenters therefore request that EPA not take action to give legal effect to these submitted 

budgets without first providing an opportunity for notice and comment pursuant to 5 USC § 553. 

II. ATTAINMENT DEMONSTRATION DOES NOT PROVIDE FOR 

ATTAINMENT IN COMMUNITIES ADJACENT TO HEAVILY TRAVELED 

FREEWAYS. 

The attainment demonstration in the adopted AQMP does not estimate the emissions 

reductions that will be needed to attain either the annual or the 24-hour NAAQS for PM2.5 in the 

near-highway environment where primary particles emitted from motor vehicles and re-entrained 

dust cause or contribute to concentrations well-above those used to determine the design value for 

the region and the regional attainment demonstration. Emissions from heavily traveled freeways 

have been shown to add from 1 to 14 g/m3 of elemental carbon, a major component PM2.5, to 

concentrations measured at regional monitors more than 300 to 500 meters distant from major 

highways. In the South Coast Air Basin, commenters estimate that approximately 1.5 million people 

live within this near-highway environment where elevated concentrations of PM2.5 are expected.

A. Reliable Scientific Evidence Shows Elevated PM2.5 in the Near-Highway 

Environment.

The evidence that highway emissions have a significant impact on air quality in the nearhighway environment is not new. MATES-II first identified the importance of highway emissions in 

2000. [Attached as Exhibit A]. Although MATES-II was focused on the significance of diesel 

particulate as the largest source of cancer risk in the air basin, it also provided important findings 

that demonstrated that higher levels of diesel pollution occur near highways. The Report found the 

greatest exposure to diesel PM at locations where “the dominance of mobile sources is even greater 

than at other sites.” It also found that “model results, which are more complete in describing risk 

levels...than is possible with the monitored data, show that the higher risk levels occur... near 

freeways.” “Results show that the higher pollutant concentrations generally occur near their 

emission sources.” These findings provided evidence that neighborhoods near highways would 

experience higher concentrations than the regional averages. Based on these observations, MATESII concluded that “[f]or mobile source compounds such as benzene, 1-3 butadiene, and particulates 

associated with diesel fuels, higher concentration levels are seen along freeways and freeway 

junctions.” This work identified the near-highway environment as a high risk environment where 

elevated levels of PM would be expected because of emissions from diesel vehicles. 
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This triggered further research in the region. A team from USC conducted seminal studies to 

measure the concentrations of highway pollutants as a function of distance from the I-710 and I-405 

freeways. [Attached as Exhibit B] Both studies included measurements of concentrations of CO and 

black carbon (BC) at increasing distances from the freeway. CO and BC were intentionally selected 

because their ambient concentrations are strongly related to vehicle emissions. Black carbon, also 

measured as elemental carbon (EC) in the monitoring reported in MATES-II and MATES-III 

[Attached as Exhibit C], is a species of PM2.5 that was used in the MATES-II study as a measure of 

diesel PM in the Air Basin. The MATES-III study reported more recent investigations showing that 

elemental carbon is an inadequate measure of diesel PM, and that other methods show that total 

diesel PM is at least 72% greater than elemental carbon. MATES-III, p. 2-9. The AQMP relies on 

the MATES-III data to identify elemental carbon as one of the six major species of PM2.5 in the 

South Coast air shed that contribute significantly to PM2.5 nonattainment. 

The freeway studies show the dramatic increase in BC/EC in the near-highway environment. 

The studies measured concentrations at five distances downwind from the freeway and upwind from 

the freeways. By comparing the upwind measurements which provide a good estimate of regional 

carbon loadings in the Air Basin with the downwind measurements, these studies provide a good 

estimate of the increase in concentrations of primary carbon particles emitted from highways in the 

vicinity of major highways compared to regional concentrations measured in the urban air shed. 

The BC measurements from each of the freeway studies are summarized separately below 

along with measured upper and lower limits, and the observed difference between the comparable 

upwind and downwind BC concentrations:

Measured Average (and Upper and Lower Limit) BC Concentrations at Increasing Distances 

from the 405 Freeway 

Downwind Distance (m) BC (μg/m3) BC (μg/m3) DownwindUpwind Average 

Concentration

30 5.4 (3.4-10.0) 4.75 

60 3.2 (3.0-3.5) 2.55 

90 2.5 (2.4-2.6) 1.85 

150 1.6 (1.1-2.0) 0.95 

300 1.3 (1.1-1.5) 0.65 
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Measured Average (and Upper and Lower Limit) BC Concentrations at Increasing Distances 

from the 710 Freeway 

Downwind Distance (m) BC (μg/m3) BC (μg/m3) DownwindUpwind Average 

Concentration

200 m (upwind) 4.6 (3.1-5.9) 

17 m 21.7 (20.3-24.8) 17.1 

20 19.4 (16.5-21.6) 14.8 

30 17.1 (12.6-19.3) 12.5 

90 7.8 (4.5-9.3) 3.2 

150 6.5 (3.9-9.2) 1.9 

300 5.5 (3.5-7.7) 0.9 

Notice the large increase in the near-highway concentrations of BC downwind of the I-710 

compared to the I-405. The Interstate 710 study was conducted in part because the freeway has a 

much higher percentage of heavy-duty diesel truck travel than the Interstate 405 freeway. Average 

traffic flow during sampling periods was 12,180 vehicles per hour with more than 25 percent of 

vehicles being heavy-duty diesel trucks. This is perhaps the highest density of diesel truck traffic 

anywhere in the U.S. Measurements were taken at 17, 20, 30, 90, 150 and 300 meters downwind 

and 200 meters upwind from the center of the freeway. As with the 405 freeway study, relative 

concentrations of CO and BC downwind from the freeway were found to be many micrograms per 

cubic meter greater than upwind concentrations and tracked each other well as one moves away 

from the freeway. 

These studies show that in the impact zone downwind of a heavily traveled freeway in the 

Air Basin with average truck traffic (I-405), emissions of BC from the freeway will add 4.75 g/m3

to PM2.5 at 30 meters from the freeway dropping off to 0.65 g/m3 greater than the regional 

concentration at 300 meters, and that a freeway with heavy truck traffic will add 12.5 g/m3 at 30 

meters dropping off a 1.9 g/m3 increase above the regional levels at 300 meters. 

The incremental effect of highway emissions downwind from the I-710 have been 

confirmed in recent weeks by data released as part of the deployment of Mobile Monitoring 

Platform Results in the I-710 corridor. See Mobile Monitoring Platform Update and Results 

reported by CARB, April17, 2008, at the HCMS Community Meeting, Wilmington Senior Center. 

[Attached as Exhibit D]. These results include BC concentrations within the so-called buffer zone 

500 feet from the freeway compared with results measured beyond the 500 feet buffer. 

Concentrations measured in West Long Beach residential area on the morning of July 17, 2007, 

show nearly a four-fold greater BC level within 500 feet from the 710 freeway compared to the 

same neighborhood outside the 500 feet zone (18 vs 5 g/m3). This difference of 13 g/m3 is 

highly consistent with the upwind/downwind results reported in the original 710 study.

These results were supported by measurements made in other regions. A study in Seattle, 

WA (Curtis, Gilroy, and Harper, 2004) measured the relationship between BC levels at an urban 

near-roadway monitoring site, and a heavily traveled freeway. [Attached as Exhibit E] This study 
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showed that there were frequently peak evening rush hour BC levels of 5 μg/m3 or above near I-5. 

The BC data was obtained from the Olive Street monitoring site located at the EPA-designated 

microscale within the I-5 traffic corridor. The traffic volumes and BC readings correlate well, 

supporting the hypothesis that traffic is a major contributor to PM2.5 at the site, given that BC 

originates from motor vehicle exhausts as ultrafine or fine particles. The Olive Street air monitoring 

site is about 20 meters west of the southbound lane of I-5 in the CBD. This area of I-5 contains 

express lanes along with several high use overpasses which all contribute to the area traffic. Daily 

volumes along this section of I-5 average 284,700 vehicles per day (in 2003). Light-duty traffic has 

peak weekday flows above 10,000 vehicles per hour, with diesel traffic of about 1,000 vehicles per 

hour (10%). BC tends to peak during weekdays with high traffic volumes, and is sharply lower on 

weekends. This reduction parallels the significantly lower weekend diesel traffic volumes. Peak BC 

measurements occur during the afternoon rush hour (4-6 pm). Correlations between light-duty 

vehicle volumes and BC peaks (readings above 5 μg/m3) are better than those between diesel truck 

volumes and BC peaks. This may occur because light-duty volumes overwhelm diesel truck 

volumes during this peak period (93 percent of the traffic volume is from light-duty vehicles). 

The Seattle study also measured BC at a Beacon Hill site about 600 meters from a major 

freeway, which is used as the urban background for Seattle. Hourly BC readings during the study 

period stayed within the range of 0 to 2 μg/m3, with readings mostly below 1.0 μg/m3. Comparing 

these sites demonstrates results similar to the data obtained from the I-405 study with BC 

concentrations in the near-highway environment being about 4 μg/m3 greater than the urban 

regional concentration.

The East Bay (California) Children’s Respiratory Health study (Kim et al., 2004), conducted 

with support from Cal EPA’s Office of Environmental Health Hazard Assessment, obtained 

measurements of PM2.5 concentrations at monitors located in the schoolyards of 10 middle schools 

in communities across the East Bay. [Attached as Exhibit F] This study reported the distance of 

each monitor from major freeways, the traffic density on the nearest freeway, and whether the 

school was located downwind of the traffic source. The PM2.5 measured at the school closest to (60 

meters), and downwind from a major freeway, was 15 μg/m3 which was 3 μg/m3 greater than the 

12 μg/m3 PM2.5 concentrations reported at the regional air district network monitor located about 1 

mile from major traffic sources. 

The recently released West Oakland Health Risk Assessment conducted by the ARB 

provides similar results from a modeling study that shows highly elevated concentrations of diesel 

PM in a neighborhood downwind of the Port of Oakland and surrounded by heavily traveled major 

freeways. [Attached as Exhibit G—but appendicies A through E not attached and available at 

http://www.arb.ca.gov/ch/communities/ra/westoakland/westoakland.htm]. The risk assessment 

showed that despite the significant contribution of emissions from ocean going vessels, local 

watercraft, railyard and port activities, the emissions from non-port related on-road truck operations 

accounted for 80% of the diesel PM in West Oakland. 

These and other studies provide credible evidence that PM2.5 concentrations in the nearhighway environment are expected to range from 3 μg/m3 to as much as 13 μg/m3 greater than 
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concentrations measured at regional monitors located outside the high impact zone of heavily 

traveled freeways.

 Data from these highway studies were expressly relied upon by US EPA to decide that it 

must establish a transportation conformity program to review the localized impacts of PM2.5 

emissions from highways. See Transportation “hot spot” rule, 71 Fed.Reg. 12468, 12494 (March 

10, 2006). EPA concluded that the evidence of localized impacts from highways was sufficiently 

compelling to require that “it is essential that a quantitative PM2.5 or PM10 hot-spot analysis be 

performed for all projects of air quality concern.” Id. If the evidence of localized impacts was 

sufficient to justify a national regulatory program to protect against NAAQS violations caused by 

new highways, it is also compelling enough to require a quantitative analysis to ensure that the SIP 

will protect against existing localized NAAQS violations caused by highway emissions.

B. Exposed Population in Near-Highway Environment is Significant. 

To determine the public health significance of human exposures to the elevated 

concentrations occurring in the near-highway environment, Environmental Defense Fund performed 

an exposure analysis that plotted all limited access highway links in the South Coast air Basin with 

annual average daily traffic (AADT) greater than 125,000, and then used available 2000 census data 

to estimate the population within 300 meters of these highway links.3

 The 125,000 AADT threshold 

was selected based upon EPA’s determination that this is an appropriate traffic threshold for 

identifying highway “projects of air quality concern” as a trigger for performing a transportation 

“hot spot” analysis for PM2.5. See 71 Fed. Reg. 12,468. The 300 meter impact zone is based on the 

evidence discussed above showing that the elevated BC and PM2.5 concentrations associated with 

highway emissions is significant at 300 meters from highways. This analysis shows that 

approximately 1.5 million citizens within the SCAB reside within the 300 meter high impact zone 

adjacent to major freeways. 

C. Attainment Demonstration Fails to Protect Against Elevated PM2.5 in the 

Near-Highway Environment. 

The PM2.5 concentrations expected in the near-highway environment are not reflected in the 

adopted attainment demonstration because neither the monitored concentrations of PM2.5 used to 

select the design value for the attainment demonstration, nor the modeling analysis used to 

demonstrate future attainment account for the increased PM2.5 concentrations in the near-roadside 

environment. 

1. Monitors Not Located to Measure PM2.5 In Near-Highway Environment. 

The monitors selected to determine the design value for the South Coast air basin are not 

located in the near-highway environment. 

3

 The methodology used and software applied to perform this analysis is explained in Exhibit H hereto. 
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The highest annual and 24-hour design values among the network sites are recorded at 

Rubidoux in Riverside County. For this reason, the measurements at this site play an important role 

in the development of the attainment demonstration. But this site is not located in a near-highway 

environment. The Site Survey Report for the monitor describes the location as residential, with 

residential traffic of only 10,000 vehicles per day within 25 meters. Based on this description of the 

site, it is apparent that the design value does not reflect the incremental impact of primary aerosols 

emitted from a nearby heavily traveled highway. 

Another site with a high design value is Fontana/Arrow Highway. The Site Report for this 

location describes the monitor as being 85 meters from an arterial roadway carrying 28500 vehicles 

per day. This is not a major highway. 

The Wilmington site is in the neighborhood west of the I-710, but it too is more than 300 

meters from the freeway and not located in the high impact area where vehicle emissions would be 

expected to contribute to higher PM2.5 concentrations.

These site locations are not in close proximity to major freeways, and do not detect the 

incremental impact of highway emissions. A control strategy that is adequate to reduce the 

concentrations at these sites to attain the NAAQS cannot be shown to reduce the higher 

concentrations in the near-highway environment to the level of the NAAQS. 

2. Large-Scale Regional Modeling Does Not Predict Impact of Reductions in Highway 

Emissions.

The modeling analysis performed for the attainment demonstration uses the CAMx model, 

which is the same model applied to demonstrate ozone attainment. This is a regional airshed model 

that aggregates emissions and estimates ambient concentrations for a grid that is made up of cells 5 

km on a side. AQMP, Appendix V, p. 2-15. But for the purpose of comparing modeling results with 

monitoring station measurements, the results are averaged over nine grid squares. “The CAMx 

modeling results are presented based on a nearest nine-grid-cell average basis. Performance 

evaluations at each station are based on this average concentration.” Id., p.2-24.

This approach may be suitable for the purpose of estimating concentrations of secondary 

species that are formed after primary pollutants are cooked in the chemical soup of the Air Basin, 

but this large scale averaging provides no useful information regarding the dispersion of primary 

pollutants emitted from large sources such as highways. 

 Unlike secondary particulate species which become particles downwind from their point 

of emission as gases, the elemental carbon and aerosol VOCs emitted from tailpipes, road dust, tire 

and brake pad particles are emitted directly from highways to the atmosphere, and are most highly 

concentrated at the source. The regional grid modeling analysis performed by CAMx aggregates 

these emissions and averages them over large regions, rather than recognizing them as being most 

highly concentrated at the point of origin. EPA explained in its guidance regarding PM attainment 

demonstrations that “[d]ispersion models are better able to capture the influence of primary PM 

sources where large concentration gradients may exist. Grid models spread out the PM emissions to 
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the size of the grid (typically 4 or 12 km). This makes it difficult to judge the benefits of control 

strategies that may affect primary PM sources.” 72 Fed. Reg. 20607-08. The large-scale regional 

modeling analysis performed for the SCAB cannot, and does not, predict concentrations of the 

primary species in the near-highway environment. Given the limitations of this large scale tool for 

predicting the impact of primary PM emissions from sources on local ambient concentrations, the 

attainment demonstration in the adopted AQMP cannot be approved as adequate to demonstrate 

attainment in the near-highway environment. 

3. Small Scale Modeling Tools Are Available. 

EPA’s modeling guidance identifies the problem we identify here, and suggests suitable 

models for assessing the expected ambient impacts of primary PM emissions on locations that are 

not represented by the monitoring network. The modeling guidance warns specifically of the 

possibility that high concentration locations affected by emissions of primary PM will be missed: 

Focusing the modeled attainment test only at monitoring sites could result in control targets 

which are too low if the monitoring network is limited or poorly designed. 

We recommend a test which includes a review of the strategy’s impact at locations without 

monitors. This exercise provides a supplemental test to determine whether there is a need for 

further action despite passing the modeled attainment test at all monitoring sites. 

“Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality 

Goals for Ozone, PM2.5, and Regional Haze,” p.19 [Attached as Exhibit I]. In the situation where 

highways are the most significant source of primary carbonaceous PM2.5, and a monitoring 

network that does not include any monitors located within the high concentration zone representing 

the exposure of populations adjacent to highways, an additional investigation is clearly required. 

Two recent studies demonstrate the modeling tools available for estimating the near-highway 

impacts of primary PM emitted from highways. The West Oakland health risk assessment uses a 

fine scale (250M x 250M) dispersion model nested with a larger scale model to identify the impacts 

of highway emissions on the adjacent community. The dispersion modeling analysis performed by 

E.H. Pechan and Associates to assess likely neighborhood scale impacts from the Intercounty 

Connector highway project in suburban Maryland also demonstrates the availability of CalQH3R 

for this application. Both modeling studies estimated near-highway impacts greater than 4 g/m3. 

[Attached as Exhibit I(a)].

III. CONTROL MEASURES NOT AVAILABLE TO DEMONSTRATE THAT 

EMISSION REDUCTIONS WILL BE ACHIEVED. 

On March 13, 2008, the Coalition for Clean Air, NRDC, and Earthjustice submitted 

comments objecting to the original emissions budgets submitted by CARB to EPA. [Attached as 

Exhibit J]. We continue to remain concerned about the issues raised in the March 13, 2008 letter, 

and for this reason have resubmitted these comments with this submission. 
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As previously articulated in that letter, longstanding US EPA policy governing the standards 

for SIP approval requires that each control measure in the SIP contain six basic elements necessary 

to provide minimum assurance that it will result in the emissions reductions credited to it. These 

elements include: 

1. evidence of adoption of the measures in legally enforceable form or a binding 

schedule for adoption;4

2. a description of each measure with “detail and clarity,” identifying which entity is 

responsible for implementation and what “actions are to be taken”;5

3. a “thorough demonstrate[ion] that the measures are capable of achieving the 

estimated emission reduction benefits.”6

4. an emission reduction estimate for each measure;7

5. provisions for monitoring and reporting on implementation and effectiveness;8

6. an “identification of and commitment to the financial and manpower resources 

necessary to carry out the plan.”9

Many of the measures in California’s SIP submittal do not meet these requirements. We are 

particularly concerned that CARB in its pursuit of flexibility has crafted the form of the 

commitments made throughout the SIP in such a way that it prevents enforcement by US EPA or 

anyone else seeking to enforce this SIP. Furthermore we are very concerned that many of the 

measures in the SIP lack sufficient specificity to quantify the reductions that could be achieved, be 

implemented to ensure reductions at the level claimed for the measure, monitored for progress, and 

enforced.

The current submission also does not comply with section 110(k)(4) of the Act, which notes 

that EPA “may approve a plan revision based on a commitment of the State to adopt specific 

enforceable measures by a date certain, but not later than 1 year after the date of approval of the 

plan revision.” There must be a commitment by CARB and/or the SCAQMD to adopt enforceable 

measures within 1 year of a conditional approval by EPA. Since additional enforceable 

commitments are necessary to reach attainment and one or more RFP milestones, EPA cannot at 

this time conditionally approve the plan. 

Moreover, additional emissions reductions are not solely necessary to meet attainment after 

the last milestone year, but rather are required to meet one or more RFP milestones. There are four 

additional comments worth referencing at this time. 

First, given that the Pacific Merchant Shipping Association succeeded in PMSA v. 

Goldstene, No. 07-16695 (9th Cir. 2008), the challenged CARB’s Auxiliary Engine Rule is set 

aside and may not be enforced until EPA grants a waiver. Until EPA grants the waiver, the 

associated emissions reductions may not be credited toward the reductions in the SIP for the 

4 See 43 Fed. Reg. 21,673-75 (May 19, 1978) 5

 55 Fed. Reg. 36456, 36487 (Sept. 5, 1990). 6 Id.

7 Id.

8

 55 Fed. Reg. at 36487. 

9 Id.
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purpose of setting emissions budgets for the South Coast. Moreover, the United States Court of 

Appeals for the Ninth Circuit recently denied a petition for re-hearing. It is our understanding that 

under both sets of budgets submitted by CARB reductions associated with the Auxiliary Engine 

regulation are assumed as achieving reductions during all milestone period because this regulation 

was adopted prior to October of 2006. Since the emissions reduction associated with this regulation 

cannot be credited until further action by EPA, CARB cannot take credit for them. 

Second, in Table 4, there is an assumption that 10 tpd of NOx in 2014 will come from 

federal reductions, namely reduction in pollution from locomotives. To date, the US EPA has not 

taken action needed to achieve these reductions. The budgets cannot assume these emissions 

reductions.

Third, the South Coast Air Quality Management District (“SCAQMD”) is set to vote on the 

Surplus Off-Road Opt-In for NOx Program and Adopt Proposed Rule 2449 – Control of Oxides of 

Nitrogen Emissions from Off-Road Diesel Vehicles on May 2nd, 2008. Currently, there is an 

option to have this program be either mandatory or voluntary. If the SCAQMD Governing Board 

decides to implement a voluntary program, the 12 tpd of NOx emissions reductions assumed within 

the SIP cannot be assumed within the budgets. Until the Board acts, credit may not be taken for 

these reductions.

Fourth, since the submission of the March 13th letter, we have identified a deficiency in the 

SIP and associated budgets related to failure to include additional commitments on rail pollution. 

CARB's own 2007 and 2008 risk assessment for California railyards shows significantly increased 

air toxic cancer and non-cancer health risks. PM2.5 primary and precursor emissions also are 

documented. For example, CARB's April 16, 2008 draft health risk assessment for residential areas 

adjacent to the San Bernardino BNSF railyard showed high levels of criteria and greenhouse 

pollutants emitted by California railyards. In fact, CARB’s 2007 SIP strategy documents admit that 

the severity of the region's PM2.5 problem and the attainment deadline make it necessary to further 

mitigate locomotive emissions in 2014.” 

 In the absence of demonstrated reductions from the federal new locomotive rule sufficient to 

achieve the reductions assumed in the AQMP, the State must adopt rules sufficient to make up the 

shortfall between the federal rule and the reductions assumed in the AQMP before these reductions 

can be assumed for RFP purposes. The State has regulatory options available to achieve these 

reductions.

Federal pre-emption of the regulation of railyard sources is limited to new engines and 

engine remanufacture. US EPA's analysis in support of its new locomotive regulations admits that 

the Act does not, for example, pre-empt switcher locomotive rules which “may be subject to 

regulation by California and other states.” See 72 Fed. Reg. 15971. According to CARB's own 

models, switchers are responsible for 11% of the total PM emissions from the four Commerce 

Railyards. The CAA pre-emption for the regulation of new engines also does not prevent the State 

from regulating the use of engines, including the number of engines operating in a yard, the hours of 

operation, or the meteorological conditions under which operations may be permitted. Just as the 
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Act does not limit a state’s authority to regulate the use of motor vehicles, it also does not limit 

authority to regulate the use of other mobile sources. 

Appropriately tailored measures to achieve the PM2.5 reductions from locomotives assumed 

in the SIP should include: 

1. CARB adoption of South Coast AQMD Rules 3501-3503 for idling limits, 

recordkeeping and modeling rules for all interstate and intrastate 

locomotives; 

2. Rules that limit switcher locomotive to 15 minute idling, as well as rules that 

require the retrofit of switcher locomotives for the purpose of emission 

reduction

3. Idling and plug-in rules for refrigerated units while not in transit 

4. In-use testing for compliance with federal standards 

5. Remote sensing for compliance with federal standards 

6. Diesel particulate filters on all interstate and intrastate locomotives 

7. Idling regulations for locomotive maintenance facilities and /or stationary 

emission control device regulations (such as hood technology) 

8. Stepped-up enforcement with more rigorous standards than the 2005 MOU 

9. Regulatory measure that requires the development and implementation of 

emissions reduction plan for each Railyard with components that address 

proximity to sensitive receptors 

10. Electric rail-mounted container gantry cranes 

CONCLUSION. 

Until CARB submits an attainment demonstration for PM2.5 that provides for attainment in 

the near-highway environment, and the measures needed to achieve the reductions required to attain 

are identified, quantified and adopted in legally enforceable form, it is premature to establish any 

emission budgets for PM2.5 emissions from motor vehicles. In addition, until the measures needed 

to achieve reasonable further progress for ozone are adopted, proposed RFP budgets for ozone 

cannot be adequate. We therefore ask EPA to postpone action on the submitted interim budgets 

until these deficiencies in the AQMP are remedied. 

 Respectfully submitted April 28, 2008.