Study shows how electric transport and urban design help us meet climate goals


New research from the Institute for Transportation Development Policy (ITDP) and the University of California, Davis (UC Davis) concludes that electric cars alone won’t save us – the only way to stay below 2, 7 degrees Fahrenheit (1.5 degrees Celsius) of warming is a combination of electrification and increased urban density. Lewis Fulton of UC Davis and D. Taylor Reich of ITDP, lead authors of the report, titled “The Compact City Scenario—Electrified,” calculated the numbers on four scenarios:


  • As per usual (BAU) where we continue to build and drive internal combustion engine (ICE) cars, with more than two billion new cars by 2050.
  • High EV where all cars are electrified at the rate announced at COP26, with sales of ICE vehicles being phased out by 2040.
  • High offset where land use is shifted to a compact mixed-use design, much like the one shown in our article, how can we build in a climate crisis. “In the world of high gear change, it is easier to get around cities on foot, by bicycle or by public transport than by car, and the demand for cars is therefore reduced. While global car use is increasing slightly due to population growth, it is much lower than under BAU or High EV.”
  • EV + Shift where a combination of High Shift compact design in walkable cities and electrification of all vehicles.

The problem with the high electric vehicle (EV) scenario is that even if cars and trucks don’t emit greenhouse gases in their exhaust, it will take far too long to change them. They will need vast new sources of clean electrical energy. And, notably, the report takes into account embodied carbon or the initial carbon emissions of manufacturing and the infrastructure that supports them, which we noted is an important but overlooked issue.

“Our scope is not limited to greenhouse gas emissions from the operation of vehicles (“Well-to-Wheel”). Rather, we include emissions from the manufacture and disposal of vehicles, which is particularly important for electric vehicles because of the carbon-intensive processes of creating batteries.We also include emissions from the construction and maintenance of infrastructure, including roads, rails, bike paths and parking spaces.

On first review I thought their initial carbon accounting was too low, but they covered that too. They write: “For vehicle production, disposal and infrastructure, we assume fairly strong decarbonization, in the order of 50-60% by 2050.”


Including embodied carbon, or manufacturing emissions, means that those dark blue bits of manufacturing emissions are important; going all-electric does not mean that in the full life cycle, emissions disappear. They are as important as the operational emissions from the not fully electrified network.


The biggest difference between just switching to High EV and combining High EV with High Shift is the number of cars on the road, which is around 300 million fewer. This also adds up to a massive reduction in the amount of electricity needed to run the transportation system.


In summary, electrifying transportation and moving to compact design is the only scenario that reduces emissions enough to stay below the curve representing the drop in emissions needed to keep global warming below 2.7°F. (1.5°C). Or as ITDP CEO Heather Thompson put it in a press release:

“We need electrification, but we won’t reach our 1.5°C target if we just focus on electric vehicles. We also need to focus on the fundamental equation of driving less, even if it’s in electric vehicles, which still require a lot of resources like clean electricity. We need high-density development that provides better access to jobs, education and services for families of all income levels without relying on cars. Walkable and bikeable cities are not only better for the economy and the environment, they are also healthier and happier for everyone. We have the evidence, and we know what needs to be done: we need an integrated approach that includes both electrification and compact development. Cities must mobilize.”

Synthesis of the LCGE and the population accommodated with a fixed land area for the four urban typologies.

npj Urban sustainability

Particularly absent from the report is the discussion of the carbon emissions that come with the change in building form that accompanies compact cities. In a previous article on the density of Goldilocks producing the lowest lifecycle carbon emissions, we noted research by Francesco Pomponi demonstrating that high-density low-rise (HDLR) design as you would have it in compact cities of the type proposed by the ITDP, has less than half the life cycle GHG emissions (LCGE per capita compared to low density low rise (LDLR) designs. And I complained in this article that “the study did not take into account transportation, which has a much lower impact per capita at high density than at low.”

Now the ITDP tells the transportation side of the story but misses the built form side. One of the study’s authors, Taylor Reich, acknowledges this, telling Treehugger that “we’re a transportation consultancy and that’s not our expertise.”

The ITDP report highlights that urban form and transport are interconnected, a point we have long tried to make in Treehugger. In the conclusion of my book, “Living the 1.5 Degree Lifestyle”, I channeled transportation planner Jarrett Walker and wrote, “How we live and how we move are not two issues distinct; they are two sides of the same coin, the same thing in different languages.”

More recently, I wrote, “We need to stop talking about transport emissions as something separate from building emissions. What we design and build determines how we move (and vice versa) and you don’t You can’t separate the two. These are all emissions from the built environment, and we need to manage them together.”

The ITDP report doesn’t quite sum it all up or give the full picture of the impact of the built form change and transportation change, but the pieces are starting to fall into place.

Reich also notes that starting to implement changes to public transportation that get people out of cars, like bus-only lanes and bike lanes, is much faster than waiting for electric cars.

“Timing is key, especially over the next ten years. Electric cars aren’t expected to go mainstream until the early 2030s, but compact city policies are ready now. If we build public transit, bike lanes, and compact neighborhoods today, we can reduce the demand for fossil-fuel car ownership. Transit-oriented planning will pave the way for easier electrification, especially in rapidly growing cities.

The compact city part of the equation takes a little longer and needs something else.

“It’s ambitious to say we can phase out internal combustion engines by 2040, and it’s ambitious to say we can redesign cities so that more than half of all travel is on foot, by bike or public transit,” but these things are logistically and technologically feasible. …all that is missing is the political will.


This chart really sums it all up, the difference that happens when you go from electrifying all those cars in the High EV scenario or keeping 300 million of them off the road, switching to other modes of transportation: greenhouse gases are about 40% lower. In addition to needing electric cars, we need fewer cars, and for that we need cities designed so that people can walk, cycle or take public transport.

And that, again, is just transport emissions; it does not include changes in building form, total emissions from the built environment. It will be an even prettier image.

You read the post, now watch the movie:


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