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Frequently Asked Questions

FHWA

Air Quality Planning and SIPs

Transportation conformity ensures that Federal funding and approval goes to those transportation activities that are consistent with air quality goals and can have a significant impact on the transportation planning process. Transportation officials must be involved in the air quality planning process to ensure that emissions inventories, emissions budgets, and transportation control measures (TCMs) are appropriate and consistent with the transportation vision of a region.

Each State air quality agency is tasked with determining how best to achieve the Clean Air Act's (CAA's) goals and with developing state implementation plans (SIPs) for achieving health-based air quality standards. In some states, local air quality agencies also play a major role in air quality planning. SIPs are collections of regulations and measures used by a State to reduce emissions from stationary, area, and mobile sources and demonstrate attainment and maintenance of air quality standards. Decisions made in the air quality planning process and during SIP development can have a direct effect on transportation plans and projectcs. Transportation agencies need to participate fully in the air quality planning process to ensure that the decisions made reflect community priorities, including mobility.

Policy

FHWA

EPA

Technical

EPA

Conformity Lapse / Grace Period

FHWA

A conformity "lapse" means that the conformity determination for a transportation plan or transportation improvement program has expired, and thus there is no currently conforming plan or transportation improvement program. During a conformity lapse, FHWA and FTA can only make approvals or grants for: Project that are exempt from the conformity process (pursuant to 93.126 and 93.127 of the conformity rule), and Transportation control measures (TCMs) that are included in approved SIPs. Only those project phases that have received approval of the project agreement and transit projects that have received a full funding grant agreement (FFGA), or equivalent approvals, prior to the conformity lapse may proceed during a conformity lapse. The conformity lapse grace period allows an additional 12 months from a missed conformity deadline for the area to correct the problem before a conformity lapse occurs.

EPA

Emissions Analysis

Policy

FHWA

EPA

Analysis

EPA

Emissions Models

EPA

Land Use

EPA

Research and applied practice have attempted to define the nature of land use and travel behavior for several decades. An increasing number of studies have suggested that land use can also indirectly influence emissions of airborne pollutants that are largely produced through the use of internal combustion engines operated in private automobiles and trucks, among other point and area sources. The theories have a similar origin, suggesting that land use patterns influence trip making frequency, trip lengths, choice of what mode of transportation to take, and so forth. The overwhelming majority of conclusions cite that land use patterns do (1) influence the trip making behavior of individuals; and (2) when measured, these travel changes in turn influence emissions from private automobiles and trucks when measured over a broad area.

Multi-Jurisdictional (Complex) Areas

FHWA

The boundaries of a metropolitan planning organization (MPO) do not always correspond to the nonattainment or maintenance area boundary, nor does a nonattainment or maintenance area always contain a single MPO. In addition, a nonattainment or maintenance area boundary may encompass portions of more than one state. Also, there may be some portion of the nonattainment or maintenance area that is not included in any MPO's planning area. The following documents provide information about transportation conformity issues related to these multi-jurisdictional areas.

  • Court Decision on Transportation Conformity Rule (October 2006) - The U.S. Court of Appeals vacated a provision of the Transportation Conformity Rule (40 CFR 93.109(e)(2)(v)), a provision that allowed areas to use the interim emissions tests instead of the 1-hour budgets where the interim tests could be shown to be more appropriate for ensuring that the plan, TIP, or project would not create new violations, worsen existing violations, or delay timely attainment of the 8-hour standard, as determined through interagency consultation.

EPA

NAAQS and Designations

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. The EPA Office of Air Quality Planning and Standards (OAQPS) has set National Ambient Air Quality Standards for six principal pollutants (Particulate Matter, Ozone, Carbon Monoxide, Nitrogen Dioxide, Lead, Sulfur Dioxide), which are called "criteria" pollutants. Transportation conformity applies to particulate matter, ozone, carbon monoxide, and nitrogen dioxide.

Ozone

EPA

Particulate Matter

FHWA

EPA

Project Level Conformity

Project level conformity determinations require that the FHWA/FTA project must come from a conforming transportation plan/TIP or associated regional emissions analysis. In addition, in carbon monoxide and particulate matter nonattainment and maintenance areas, an analysis of localized emissions may be required for federally funded or approved projects. This analysis is called a "hot-spot" analysis.

FHWA

EPA

Transportation Control Measures

FHWA

  • Interim Guidance for Implementing the Transportation Conformity Provisions in SAFETEA-LU (February 2006) - Memorandum from FHWA, FTA, and EPA concerning guidance on implementing the transportation conformity-related provisions contained in SAFETEA-LU - this interim guidance pertained to the time period before the federal transportation conformity rule was revised.
  • Guidance on the Implementation of the March 2, 1999 Court Decision (January 2002) - Updated guidance from FHWA and FTA concerning approval for projects in nonattainment and maintenance areas that do not have a currently conforming transportation plan and transportation improvement program. Changes resulted from a case brought against EPA by the Environmental Defense Fund.
  • Program Guidance on High Occupancy Vehicle Lanes (or PDF) (August 2008) - FHWA guidance on the planning, design, operation, and management of HOV facilities, as well as examples to follow in evaluating proposed significant changes to the operation of an HOV lane (e.g., conversion of an HOV lane to an HOT lane)

EPA

Superseded Guidance

FHWA

  • Carbon Monoxide Categorical Hot-Spot Finding (February 2014) - FHWA's 2014 carbon monoxide (CO) categorical hot-spot finding per the transportation conformity rule at 40 CFR 93.123(a)(3) for urban highway projects that include one or more intersections in CO maintenance areas, except in California. Project sponsors may be able to rely on the categorical hot-spot finding in place of doing their own CO hot-spot analysis as part of a project-level conformity determination in CO maintenance areas. *Note: This Finding was based on MOVES2010 which is no longer the latest emissions model for transportation conformity and SIP purposes as of October 7, 2016. Therefore, this Finding may no longer be relied upon for any CO hot-spot analyses begun after October 7, 2016
  • Interim Guidance for Implementing the Transportation Conformity Provisions in SAFETEA-LU (February 2006) - Memorandum from FHWA, FTA, and EPA concerning guidance on implementing the transportation conformity-related provisions contained in SAFETEA-LU - this interim guidance pertained to the time period before the federal transportation conformity rule was revised.

EPA

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Updated: 3/27/2019
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