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Transportation Conformity Practices in Complex Areas

Multi-MPO Nonattainment and Maintenance Areas

There are 26 nonattainment and maintenance areas that encompass multiple MPOs. These areas include 78 MPOs as shown in Attachment B. These areas face challenges that include:

SIP Issues:

Each State with a multi-MPO nonattainment or maintenance area must determine how motor vehicle emissions budgets will be developed. The State could choose 1) to develop a single motor vehicle emissions budget for the entire multi-MPO area within that State, or 2) to develop separate sub-area budgets for each MPO or some other subset in the multi-MPO area within that State.

If the State chooses to develop a single motor vehicle emissions budget for the entire nonattainment or maintenance area, conformity determinations for each MPO within the area are based on a regional emissions analysis done for the entire multi-MPO area and tested against the single budget. In other words, the motor vehicle emissions budget is not sub-allocated among the MPOs. 8 multi-MPO areas have followed this method, 7 of which are contained within a single State each. The eighth, Washington, DC-MD-VA, is also a multi-State area. (See Multi-State Nonattainment and Maintenance Areas and Attachment A for more information.) Multi-MPO nonattainment and maintenance areas that have a single budget for the entire area are noted Attachment B.

Five of the multi-MPO areas are also multi-State MPOs with a separate MPO in each State. (See Multi-State Nonattainment and Maintenance Areas and Attachment A for more information.) Each State in these 5 areas has separate budgets for the MPO in its portion of the nonattainment or maintenance area. MPO conformity determinations in these 5 multi-State nonattainment and maintenance areas are based on separate regional emissions analyses for each State that are tested against the separate budgets for each State independently.

Seven of the multi-MPO areas are contained within a single State, and the SIPs in these areas allocate sub-area budgets for each MPO, or some other subset, such as per county. In other words, the State has negotiated allowable emissions for each sub-area, and the SIP specifically identifies the portion of the motor vehicle emissions budget that applies to each sub-area. MPO conformity determinations in these multi-MPO areas are based on separate regional emissions analyses for each sub-area that are tested against the sub-area budgets independently. Therefore, when sub-area budgets are in place, conformity in one sub-area is not entirely dependent on conformity in another sub-area. However, all sub-areas within a single State's portion of a nonattainment or maintenance area must be in conformity in order for any MPO within that State's portion of the nonattainment or maintenance area to make a conformity determination. In other words, if conformity lapses for one MPO with a separate sub-area budget, the other MPOs within that State's portion of the nonattainment or maintenance area will not lapse immediately, but they will be unable to make new conformity determinations until the first MPO once again determines conformity. Attachment B also notes the multi-MPO areas that have sub-area budgets.

The North Carolina Department of Environment and Natural Resources (DENR) has, in the past, apportioned VMT by county in order to develop countywide motor vehicle emissions budgets. The North Carolina Department of Transportation has provided speed, VMT, and vehicle mix and age distribution by peak, off-peak, and balance of day to the DENR. DENR has used this information to calculate emissions at the county level. During the most recent agency comment period, the North Carolina DOT asked for safety margins to be added to the 1-hour maintenance SIP motor vehicle emission budgets for the Raleigh/Durham maintenance area. The DENR agreed to adjust the budgets in some years and for part of the maintenance area. For a complete explanation of how the DENR allocated safety margins in the recent 1-hour ozone maintenance plans, please see: http://daq.state.nc.us/cgi-bin/parsePdf1.cgi?file=/rules/Rrules/Hearing/One_hour_maintenance.pdf (or the PDF at http://daq.state.nc.us/rules/Rrules/Hearing/One_hour_maintenance.pdf).

Three of the multi-MPO areas (Boston-Lawrence-Worcester, MA-NH; New York-N. New Jersey-Long Island, NY-NJ-CT; and Philadelphia-Wilmington-Trenton, PA-NJ-DE-ME) demonstrate even further complexity. These 3 areas are also multi-State areas. Each of these areas has separate budgets for each State. However, these areas also have multiple MPOs within a single State or States. For the Boston and New York areas, each State has a single budget that is not sub-allocated to the multiple MPOs in Massachusetts, New Hampshire, Connecticut, and New York. However, for the multiple MPOs in the New Jersey and Delaware portions of the Philadelphia area, the SIPs do sub-allocated sub-area budgets to each MPO. For more information on these areas, please see Attachment B.

Of the remaining 3 multi-MPO areas, 2 of them do not currently have budgets in their SIPs. Therefore, conformity is determined using an emissions reduction test. The other multi-MPO area, Saginaw-Bay City-Midland, MI, has a limited 1-hour ozone maintenance plan, in which motor vehicle emissions are unconstrained, and a regional emissions analysis is not required for conformity. These areas are also noted in Attachment B.

Institutional Arrangements:

A key challenge in multi-MPO nonattainment and maintenance areas is the coordination of the conformity process between MPOs. Two distinct approaches exist for the conformity processes in these areas. One approach is that the State DOT takes the lead in developing the conformity analysis, as is the case in Connecticut where 9 MPOs are part of 2 nonattainment areas. This is also the case in Massachusetts where 10 MPOs are part of 2 nonattainment areas.

For example, in Connecticut, the State DOT sets the transportation planning and conformity schedule to ensure coordination between all the MPOs and the State DOT. Also, in Ohio, an agreement is under development that will address the coordination of schedules between MPOs.

The other approach is that the MPOs use interagency consultation to coordinate the conformity analysis, as is the case in the San Joaquin Valley nonattainment area in California, where each of the 8 MPOs within the nonattainment area conducts its own modeling. Another example is the Tampa-St. Petersburg-Clearwater, FL 1-hour ozone maintenance area, where the Pinellas and Hillsborough MPOs take the lead on travel demand and emissions modeling and coordinate their activities to ensure a smoothly running conformity process. Each MPO has a separate approved motor vehicle emissions budget (subarea budgets) for 2005 and 2015. The Florida Department of Environmental Protection (DEP) and the State Department of Transportation also play a key role in coordinating the conformity process for all of the MPOs in nonattainment and maintenance areas in Florida.

Approximately half of these areas have regularly scheduled interagency consultation meetings, with about a quarter of the areas meeting monthly and a quarter of the areas meeting annually. In the other half of the cases, the MPOs indicate that the interagency consultation meetings are held on an as needed basis. Due to the fact that many of these areas have separate or sub-area budgets as discussed above, frequent coordination between the MPOs is not as prevalent. However, in areas where a single budget is used for the entire area, coordination is essential.

In most cases, where agreements do not exist or where interagency consultation is not the forum for establishing schedules, the State DOT sets the schedule for transportation planning. State DOTs in Maine, New York, North Carolina, Virginia, Ohio, Michigan, Connecticut, California, Pennsylvania and New Hampshire set the transportation planning schedules, especially for TIP updates, which must be coordinated with State Transportation Improvement Programs (STIP) for transmittal to U.S. DOT (FHWA/FTA).

Analysis issues:

Attachment B also notes for each multi-MPO area which agency takes the lead for travel demand modeling and which agency takes the lead for emissions modeling. As the attachment shows, the same agency takes the lead on both travel demand and emissions modeling in most cases although there are some notable exceptions. In Massachusetts, the MPOs take the lead on travel demand modeling, but the State DOT takes the lead on emissions modeling. Another exception is North Carolina, where the State DOT takes the lead on travel demand modeling in most cases, and the State air agency takes the lead on emissions modeling. Also, in New York State, the MPOs take the lead on travel demand modeling, while the State DOT takes the lead on emissions modeling.

The majority of the areas indicated that the motor vehicle emissions budget was being updated using MOBILE6 prior to their next conformity determination. Local data inputs for MOBILE6 were available in a large number of these areas and examples include VMT, speed, and meteorological data. In addition, about two-thirds of the MPOs in the multi-MPO areas have origin-destination data and local road and speed data that they are using in conformity.

Updated: 07/06/2011
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