Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration
Office of Planning, Environment, & Realty (HEP)

Limited Maintenance Plans - September 7, 2001


The purpose of this message is to alert you to the availability of new guidance from EPA on the use of limited maintenance plans in certain moderate PM-10 nonattainment areas. We also wish to discuss the conformity implications of these plans, as well as limited maintenance plans in ozone and carbon monoxide nonattainment areas.

On August 21, 2001, EPA issued a memorandum discussing a limited maintenance plan option for moderate PM-10 nonattainment areas. This memorandum and its appendix can be found on EPA's website at:

In short, the limited maintenance plan option may allow certain moderate PM-10 nonattainment areas to be redesignated to attainment with a streamlined maintenance plan, if they meet the defined criteria. One element of such a limited maintenance plan is that motor vehicle emissions budgets are treated as unconstrained for the length of the maintenance period. In other words, motor vehicle emissions from the planned highway and transit system are not limited and do not have to be less than a defined budget. This element of the limited PM-10 maintenance plans would be similar to how motor vehicle emissions are treated in limited maintenance plans for ozone and carbon monoxide. EPA previously released guidance on ozone and carbon monoxide areas, and this guidance can be found in Appendix J of the Transportation Conformity Reference Guide.

Since for transportation conformity purposes, EPA would be concluding that emissions in areas with limited maintenance plans need not be capped for the maintenance period, a regional emissions analysis and associated "budget test" (40 CFR 93.118 and 93.119) would not be required. However, since these areas are still maintenance areas, transportation conformity determinations are still required for transportation plans, programs, and projects. Transportation plans, TIPs, and projects must still meet the criteria for consultation and TCMs in the conformity rule (40 CFR 93.112 and 93.113). In addition, projects in CO areas with limited maintenance plans would still have to meet the criteria for CO hot spots (40 CFR 93.116 and 93.123), and projects in PM-10 areas would have to meet the criteria for PM-10 hot spots (40 CFR 93.116 and 93.123) and PM-10 control measures (40 CFR 93.117).

The conformity determination should note that a regional emission analysis is not required because the area has an approved limited maintenance plan.

If the limited maintenance plan criteria are no longer satisfied and a full maintenance plan must be developed to meet the Clean Air Act requirements, the approval of the limited maintenance plan would remain applicable for conformity purposes only until the full maintenance plan is submitted and EPA has found the motor vehicle emissions budgets adequate for conformity purposes.

If you have any questions regarding the conformity requirements for areas with limited maintenance plans, please contact Cecilia Ho at or (202) 366-9862 or Cecilia Ho at or (202) 366-2048.

Updated: 10/20/2015
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000