Not all reviews are created equally, however, nor do
they measure identical features, which is why sometimes the results can seem confusing.
CARB merely maintains the fact that pollution control and fuel economy are not
identical — fuel economy and pollution control regulations have different policy objectives, utilize different incentive and flexibility
features, and there are technologies that reduce pollution that are not counted under fuel economy
measures, and some fuel economy improvements do not reduce emissions commensurately.31