For today's post I would like to quote the nationally renowned transportation policy expert, and multiple time presidential adviser, Robert Poole of the Reason Foundation:
The premise [that smart growth reduces green house gases] goes something like this. Transportation is a major source of greenhouse gas (GHG) emissions, and personal vehicles are a significant fraction of transportation. The more people drive, the more GHGs their vehicles emit. If their job, school, shopping, etc. are close to where they live, they won’t drive as much (since they could walk or use transit). Therefore, government should force all new development to be high-density and transit-friendly, as a powerful tool for GHG reduction.
By the time you get to the end of this “logic” chain, you are actually looking at minuscule reductions in GHGs, as many different analyses have pointed out.
First, while transportation represents about 28% of GHG emissions in the United States today (according to the EPA), passenger cars are only 34% of that, or 9.5% of the total.
Second, over the next several decades, GHG emissions per mile driven will likely drop significantly, thanks to federal and state (e.g., California) measures to require increased fuel economy and encourage alternative propulsion sources (such as plug-in hybrids).
Third, densifying development applies almost entirely to new development, leaving the vast majority of the already built environment unchanged.
Fourth, just because transit is nearby does not mean it takes you where you need to go. Since most commuting is suburb-to-suburb while transit works best on radial routes to a central business district, it’s unlikely to capture much additional commute mode share. And since most people don'’t want to walk to a corner store and pay high prices, they will still drive their cars to Target or Costco to load up on good values.