# Presentation: 069621

## PM2.5 SIPs and Transportation Conformity

- Meg Patulski, USEPA/OTAQ
- Chicago PM2.5 Workshop
- June 20, 2007

## 
Motor vehicle emissions budgets for transportation conformity

Insignificance for conformity purposes

Direct PM2.5 budgets

Precursor budgets

- Motor vehicle emissions budgets for transportation conformity
- Insignificance for conformity purposes
- Direct PM2.5 budgets
- Precursor budgets

**Overview**

## Motor Vehicle Emissions Budgets

- The transportation conformity rule defines the term “motor vehicle emissions budget”
- A budget is the on-road mobile source portion of the SIP’s overall emissions inventory
- RFP plans, attainment demonstrations, and maintenance plans contain budgets
- Transportation conformity enforces SIP budgets as a ceiling

## Insignificance under Transportation Conformity

- The conformity rule allows States to _not_ create a SIP budget when:
- A pollutant or precursor is significant to the SIP’s overall strategy, but
- The on-road portion of this overall strategy is insignificant
- This provision does not affect when PM2.5 precursors are considered significant or insignificant from a broader PM2.5 SIP planning perspective (more in later slides)

## Insignificance under Transportation Conformity

- 40 CFR 93.109(k) has factors to consider:
- % of on-road emissions in context of total inventory
- Current state of air quality per monitoring data
- Absence of on-road controls, and
- Historical trends and future growth projections of on-road emissions
- Conformity provision used in limited cases
- E.g.,: small PM10 areas dominated by stationary or area sources (no PM10 budget), small ozone areas with large biogenic sources (no VOC budget)

## SIPs must include a direct PM2.5 budget for conformity purposes, unless on-road regional emissions are determined to be insignificant under 40 CFR 93.109(k) of the conformity rule

Direct PM2.5 budgets would always include on-road vehicle exhaust and brake and tire wear emissions

Re-entrained road dust and highway and transit construction dust would only be included in limited cases (i.e., when these dust emissions are a significant contributor)

- Direct PM2.5 budgets would always include on-road vehicle exhaust and brake and tire wear emissions
- Re-entrained road dust and highway and transit construction dust would only be included in limited cases (i.e., when these dust emissions are a significant contributor)

**Direct PM****2.5**** Budgets**

## A budget would be established for a PM2.5 precursor if on-road emissions need to be addressed to attain 
E.g., where NOx is considered an attainment plan precursor, and on-road emissions are significant

A budget would not be established for a PM2.5 precursor if on-road emissions were considered insignificant to attain
E.g., where VOC or ammonia is not an attainment plan precursor for the overall SIP strategy
E.g., where on-road SO2 is considered insignificant

- E.g., where NOx is considered an attainment plan precursor, and on-road emissions are significant
- A budget _would not_ be established for a PM2.5 precursor if on-road emissions were considered insignificant to attain
- E.g., where VOC or ammonia is not an attainment plan precursor for the overall SIP strategy
- E.g., where on-road SO2 is considered insignificant

**PM****2.5**** Precursor Budgets**

## Clearly identify on-road budgets that are established

Document how insignificance was determined under 40 CFR 93.109(k), when applicable

Use the latest motor vehicle emissions factor model
MOBILE6.2 for vehicle emissions (CA has its own model)
If road dust is significant, use AP-42 or EPA-approved local method

Use the latest planning assumptions that are available

Consult with metropolitan planning organizations and other transportation agencies when developing budgets

- Document how insignificance was determined under 40 CFR 93.109(k), when applicable
- Use the latest motor vehicle emissions factor model
- MOBILE6.2 for vehicle emissions (CA has its own model)
- If road dust is significant, use AP-42 or EPA-approved local method
- Use the latest planning assumptions that are available
- Consult with metropolitan planning organizations and other transportation agencies when developing budgets

**Other Considerations for Budgets**