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

The Congestion Mitigation and Air Quality Improvement Program

The Response

Note: This information was archived in September 2013. For current information, see

The Congestion Mitigation and Air Quality Improvement Program

In 1990, Congress amended the Clean Air Act to accelerate America's efforts to attain the NAAQS. The amendments required further reductions in the amount of permissible tailpipe emissions, initiated more stringent control measures in areas that still failed to attain the NAAQS (nonattainment areas), and provided for a stronger, more rigorous linkage between transportation and air quality planning. The following year, Congress adopted the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991. This law authorized the Congestion Mitigation and Air Quality Improvement Program (CMAQ) to provide funding for surface transportation and other related projects that contribute to air quality improvements and congestion mitigation. The CAA amendments, ISTEA and the CMAQ program together were intended to realign the focus of transportation planning toward a more inclusive, environmentally-sensitive, and multimodal approach to addressing transportation problems.

CMAQ and Air Quality

The main goal of the CMAQ Program is to fund transportation projects that reduce emissions in nonattainment and maintenance areas. Using State Departments of Transportation (State DOTs) estimates in 1997, total emissions reductions nationwide for CMAQ-funded projects were 170 tons per day for VOC and 430 tons per day for CO. While small in comparison to the reductions needed to attain the NAAQS, CMAQ funding has been proven to assist State DOTs and MPOs to meet their emission reduction requirements. Typically, under ISTEA, 89 percent of CMAQ-funded activities result in an estimated benefit of fewer than 100 kg/day or less while a much smaller percentage show significantly greater benefits. Figure 5 shows the distribution of expected VOC reductions for CMAQ-funded projects nationwide for FY 1997.

Figure 5. Expected Emission Reductions (VOC) FY 1997
<1: 129; 1-5: 262; 6-10: 107; 11-15: 48; 16-20: 21; 21-25: 23; 26-30: 16; 31-35: 17; 36-40: 9; 41-45: 18; 46-50: 3; 51-55: 8; 56-60: 1; 61-65: 11; 66-70: 8; 71-75: 2; 76-80: 1; 81-85: 1; 86-90: 2; 91-95: 2; 96-100: 4; 101-1000: 63; >1000: 12
Emissions reductions are provided without comment to their accuracy.


Figure 6 4. VMT Versus Lane Mileage
Years 1980-1998: VMT has increased with approx 30 degree slope where the Lane Mile Index has increased only very slightly

The most effective CMAQ-funded projects tend to be large in scope and those that directly affect vehicle emissions, for example, Inspection and Maintenance VOC reductions range from 2 to 17 tons per day.3

CMAQ and Congestion Relief

Congestion mitigation is also a goal of the CMAQ Program. Congestion relief can contribute to improvements in air quality by reducing travel delays, engine idle time and unproductive fuel consumption. And while emissions are generally being reduced nationally, most metropolitan areas are experiencing increases in congestion. Over the past twenty-five years, vehicle miles traveled (VMT) have more than doubled, while lane miles have increased slightly. (See Figure 6). This means that people are driving more and over a relatively static surface transportation system which is causing increased congestion.

Reductions in traffic congestion may decrease mobile source emissions as well as improve local economic competitiveness and productivity. However, given our current investment patterns, increasing levels of congestion are likely in the coming years. Our current course of runaway congestion is ---less and less--- a publicly acceptable option.
In addition to the $72 billion in lost time and wasted fuel, businesses located in areas with major travel delays face added costs associated with production delays, delivery difficulties, and diminished access to clients. While one alternative is to fund additional road construction to keep pace with traffic growth, this requires large capital expenditures, as well as other social and environmental costs that many communities are increasingly unwilling to accept.

Furthermore, there just may not be enough land where the need is greatest in dense urban cores. Part of the solution for these areas is to greatly improve the efficiency of the entire transportation network by increasing vehicle occupancy through better transit services, ridesharing and other demand management strategies; and managing our road systems better through Intelligent Transportation Systems and other traffic flow improvements. These improvements offer the mobility choices to reduce congestion and emissions, and CMAQ funding can help make these a reality.5

The CMAQ program is targeted at the areas of the country with the most severe air quality problems, which unsurprisingly represent the nation's largest metropolitan areas. These areas are of tremendous importance. They account for 34 percent of the population, 45 percent of the national Gross Domestic Product, 34 percent of the employment, and comprise just 3 percent of the land area. If CMAQ funding were sub-allocated to these areas according to the federal apportionment formula applied to the States, they would receive more than 57 percent of all CMAQ funds nationally (see Table 1).

Table 1 6
Federal Fiscal Year 1999 CMAQ Apportionments for the Country's 12 Largest Metropolitan Areas*
Metropolitan Area Name Total CMAQ Funds
for Metro Area
New York City (tri-State area) $ 182.5 M
Los Angeles $ 158.7 M
Chicago $ 68.7 M
San Francisco $ 34.0 M
Philadelphia (tri-State area) $ 56.2 M
Detroit $ 24.5 M
Boston $ 50.0 M
Washington DC (tri-State area) $ 59.7 M
Dallas - Ft. Worth $ 31.3 M
Houston $ 35.6 M
Miami $ 23.0 M
Atlanta $ 24.8 M
Total $ 749.2 M
Percent of Total Apportionment 57.2%

*If suballocated according to the Federal apportionment formula

CMAQ and Livability

Smog-free urban areas with good mobility underpin sustainable development goals, and a key benefit of CMAQ-funded projects is improved livability in an urban area. Areas with significant traffic congestion and bad air pollution are consistently rated poorly by the affected populations. Congestion is cited as the cause of "road rage" and other anti-social behavior. By addressing these key needs, CMAQ funding can help an area achieve a more livable environment for its inhabitants. Other quality of life benefits can also result from CMAQ funded projects. Bicycle and pedestrian improvements can make urban life much more enjoyable.

In addition to these benefits, the CMAQ Program has many indirect benefits such as including new stakeholders in transportation decisions, fostering project innovation, enhancing intermodal planning, and promoting savings in infrastructure investment. The future success of the CMAQ Program relies upon the continued participation of a diverse group of stakeholders. This diversity results in positive benefits for communities throughout the United States, because air quality decisions are subjected to a wider variety of input from representatives throughout communities and the public

The Scale of CMAQ Projects

CMAQ funding will not "solve" an area's air quality or congestion problems. Nor can it alleviate a great many urban problems, and dramatically improve an area's livability. It is one piece of a larger mosaic that can help in specific transportation corridors. For example, about $109 billion was spent by all levels of government on highway and transit programs in 1995. CMAQ funding available to the States in that year was only about $1 billion, or just 0.9 percent. Even single, albeit major, transportation infrastructure projects can cost in the billions of dollars, far exceeding total CMAQ funding.

As instructive as this comparison is to give a relative sense of scale, the proper comparison is not to the amount spent each year to maintain and improve the transportation network but to the total value of the network. While reliable estimates are not available, that figure is generally estimated to be in the trillions of dollars. When viewed in this context, CMAQ funding can only be viewed as providing incremental improvements to such a vast network. The appropriate way to view the potential of the CMAQ program is at the project or corridor level where the benefits of a single project can make a difference.

3 Source: FHWA, 1997 CMAQ Annual Report.
4 Sources: FHWA. Highway Statistics Summary to 1995, Highway Statistics Annual Reports 1996-1998; FHWA/FTA. 1997 Status of the Nation's Surface Transportation System; BTS. Transportation Statistics Annual Report 1998
5 Source: Texas Transportation Institute. 1999 Annual Mobility Report.
6 Source: FHWA.

Updated: 9/23/2013
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000