Read on Twitter
Thread: For 2 years, I've been trying to answer a question that, despite its importance, has not been addressed adequately: what is the climate impact of the SUV boom in the US? I recently completed a working paper that seeks to quantify this impact. http://dx.doi.org/10.13140/RG.2.2.10190.59209
We already know that SUVs and other light trucks have come to dominate American roads. SUVs increased their market share from just 1.8% of new vehicles in 1975 to 43.3% in 2017, a 2,306% growth rate. Cars/sedans saw their share plummet from 80.6% to just 41% during that period.
While other papers have addressed aspects of this question, none has tackled it head on, as I attempt to do here. To answer this question, I use MY 2000-2017 data from US EPA's Automotive Trends Report https://www.epa.gov/automotive-trends
Using these data, I constructed a model of the US light-duty vehicle (LDV) fleet across the lifespan of these vehicles, some of which will be on the road until 2047. I also built 3 separate alternative fleets to compare the impact of SUVs and other light trucks.
These 3 scenarios involve fleets based on the following:
- MY 1996 vehicles (the last year when cars accounted for >60% of LDVs);
- MY 1980 vehicles (the year when cars accounted for the greatest fleet share, 83.5%); and
- EU vehicles (vehicle shares equal to those in Europe).
- MY 1996 vehicles (the last year when cars accounted for >60% of LDVs);
- MY 1980 vehicles (the year when cars accounted for the greatest fleet share, 83.5%); and
- EU vehicles (vehicle shares equal to those in Europe).
Compared to the baseline, vehicle fleets across these 3 scenarios emitted 2.1%, 8.7%, and 11.4% fewer GHG emissions per mile from 2000-2017.
Across the entire lifetimes of these LDVs, the alternative scenarios emitted from 404.3 million to 2.4 billion fewer metric tons of CO2, compared to the baseline scenario. Cumulative emissions are lowest in the EU scenario.
The emissions impact is staggering. According to EPA, the Obama administrations MY 2017-2025 CAFE standards (which Trump rolled back) would save 4.7 billion metric tons of CO2. As a result, based on these 3 scenarios, the rise of SUVs may eat away 19-75% of this benefit.
Because SUVs & other light trucks both stay on the road longer and drive more miles, this shift is also adding more VMT to American roads. Under my 3 alternative scenarios, Americans would have driven 227.8-990.9 billion fewer VMT from 2000-2017.
Ultimately, carmakers have pushed Americans to buy larger, more powerful vehicles. This effort has increased their profit margins, but it has also increased GHG emissions, put greater wear on our roads, and made the transportation system far more dangerous.
I welcome constructive feedback on this working paper, as I continue to hone the methodology and discussion. Thanks go to @kevinrinz, @HannahLebovits, and @FrontierTony for their feedback throughout this process.
The datasets that I constructed for this working paper are available here: https://drive.google.com/drive/folders/1fu7XdObgWfats-Bvd9Jydx4-BGHfXolx?usp=sharing
As an illustration of how this all works, consider the average MY 2020 car & the average MY 2020 truck SUV. The car is 25% more fuel efficient (32 vs. 23.9 mpg).
But the emissions impact really adds up if you look at the total lifespan of these vehicles.
But the emissions impact really adds up if you look at the total lifespan of these vehicles.
According to U.S. EPA, there is 90% chance that a car will be off the road by age 22, but it's 29 for SUVs.
Over the course of those 22 years, an MY 2020 car will emit 61.6 metric tons of CO2. Over those 29 years, an SUV will emit 110.7 tons, 79.7% more CO2.
Over the course of those 22 years, an MY 2020 car will emit 61.6 metric tons of CO2. Over those 29 years, an SUV will emit 110.7 tons, 79.7% more CO2.
