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.
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.
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.
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.
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.
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.