Greenhouse Gas Implications
Increasing or encouraging turnover of the vehicle fleet to lower-emitting, more-efficient vehicles would reduce GHG emissions. However, the amount of this reduction cannot be determined without better definitions on what vehicles would qualify for the program and how large the program is.
A University of Michigan study determined that the 2009 federal program had a one-time effect on GHG emissions of preventing 4.4 million metric tons of CO2e, about 0.4% of U.S. annual light-duty vehicle emissions. Of these, 3.7 million metric tons are avoided during the period of the expected remaining life of the inefficient “clunkers” and 1.5 million metric tons were avoided as consumers purchase vehicles that are more efficient than their next replacement vehicle would otherwise have been. An estimated 0.8 million metric tons are emitted as a result of premature manufacturing and disposal of vehicles. These results are sensitive to the remaining lifetime of the clunkers and to the fuel economy of new vehicles that would have been purchased in the absence of the program, suggesting important considerations and significant uncertainty for policymakers deliberating on the use of accelerated vehicle retirement programs as a part of the GHG reduction policy.
In addition to limited GHG reduction from vehicle replacement, this policy would not reduce travel demand and vehicle miles traveled (VMTs). Vehicle manufacturing, disposal, and operations (roadway construction and materials) generate some amount of GHGs with or without additional tailpipe emissions.
The state could, however, tailor this program differently from the federal program, including stricter eligibility requirements to replace the most-polluting vehicles with low- or zero-emissions vehicles. The federal program was very popular and provided for a faster turnover of highly-polluting vehicles.
Further, although the magnitude of the impact is still likely to be fairly low compared with the GHG reduction targets, there are benefits to replacing older vehicles with newer models because of reductions in tailpipe emissions of other pollutants that contribute to poor air quality, including particulate matter. New vehicles are also required to meet higher safety standards.
Simply, this type of policy would likely reduce GHGs, but the magnitude and timing of emissions reductions would depend on the size and scope of the program.