Slowdown in Vehicle Replacement Could Negatively Impact Region's Air Quality

Apr 16, 2012

The average age of all the cars and trucks on Washington area roadways is on the rise, according to a 2011 Transportation Planning Board study of vehicle registration information from Maryland, Virginia, and the District of Columbia. The trend suggests that residents and businesses in the region are waiting longer to replace aging vehicles, which could have a negative impact on air quality as the rate at which newer, more fuel-efficient vehicles hit the road slows down.

According to the study, the average age of the region's vehicle fleet increased by 1.21 years between 2005 and 2011. The majority of the change came since 2008, the last time the TPB conducted its triennial survey of the region's vehicle fleet. These trends are most likely the result of the national economic downturn that began in late 2007, as economic difficulty and uncertainty often pushes individuals, families, and businesses to delay purchases of new vehicles.

To calculate the age of the vehicle fleet, the TPB uses specialized computer software to decode Vehicle Identification Numbers (VINs) collected from the departments of motor vehicles in each of the two states in the region and the District of Columbia to determine the year, make, and model of every car or truck that is currently registered.

The TPB studies the characteristics of the region's vehicle fleet every three years, primarily for the purpose of forecasting future emissions of harmful air pollutants that result from the operation of motor vehicles with internal combustion engines. Under federal regulations, the region must demonstrate that it is on track to meet national health standards and targets for future emissions reductions in order to continue receiving federal funding for transportation. The overall age of the vehicle fleet, among other factors, can significantly affect air quality, as newer-model vehicles tend to emit less than older-model vehicles.

Currently, the Washington region has the opportunity to seek redesignation by EPA as an "attainment" area for fine particle pollution, which can lodge in the deepest tissues of the lungs and cause various health effects, including asthma and cardiovascular complications. As part of the redesignation request, the Metropolitan Washington Air Quality Committee -- which is the primary body responsible for air quality planning in the region -- would submit a maintenance plan with targets for additional, future reductions in emissions from motor vehicles.

In a recent letter to MWAQC, the TPB highlighted the findings of its 2011 study of vehicle registration information and recommended that the group consider the potential impacts of additional aging of the region's fleet of cars and trucks as it works to set emissions targets for the years 2017 and 2025. Further aging on the order of what occurred in the region between 2005 and 2011 could result in total emissions being some 15% to 20% higher than currently forecast.

Air quality planning isn't the only use for the TPB's vehicle registration study. The data can also reveal geographic patterns in the number and types of vehicles that people tend to buy, such as higher rates of vehicle ownership outside the downtown core, and differences in the mix of passenger cars versus trucks and sport-utility vehicles over time.

The main finding of the most recent study, however, is that the region's vehicle fleet is aging, which means that cars and trucks that are older and less fuel-efficient are staying on the road longer. Widespread economic recovery could reverse the aging trend by encouraging new purchases. The next vehicle survey in 2014 will shed further light on one of the most important transportation-related trends affecting air quality in the Washington region.

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