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UC Berkeley study concludes demand reduction policies on light-duty vehicles essential to meeting GHG reduction targets by 2050

Average per capita light-duty vehicle (LDV) transport CO2 emissions (kg CO2 person-1 yr-1) for a global sample of countries (2007) with a wide range of per capita incomes. Per capita transport CO2 emissions are decomposed into the product of two terms: per capita LDV use (horizontal axis, veh-km person-1 yr-1) and propulsion carbon intensity (vertical axis, g CO2 veh-km-1). Full explanation at Sager et al. Click to enlarge.

A team from the University of California, Berkeley concludes that reducing demand for light-duty vehicle (LDV) travel will likely be essential to meeting the international greenhouse gas emission and climate targets for the year 2050. Their open access paper is published in the IOP journal Environmental Research Letters.

The quest for reduced LDV emissions is often posed as a technology issue of lower-carbon fuels or more efficient vehicles, Jalel Sager, Joshua Apte, Derek Lemoine and Daniel Kammen note in their paper. However, in their study they decomposed transport sector emissions into technological and behavioral drivers, and showed that even significant technological advances will be insufficient to meet climate goals, unless the growth in LDV use slows or reverses.

While policy options aimed to reduce the need for LDV travel typically receive far less attention than do technological measures, we find such demand avoidance options are likely essential to meeting mid-century GHG reduction goals.

...We find that innovation in a single area such as fuel economy does not offer a realistic, affordable, or resilient pathway to the LDV emission reductions necessary by mid-century. Instead, as social, technical, and infrastructural drivers of LDV GHG emissions interact multiplicatively, the responsibility should be spread over a portfolio of achievable improvements across the transport system.

—Sager et al.

Sager et al. identify five potential elements for improvement in LDV GHG emissions:

  • Fuel carbon intensity and vehicle energy efficiency (together representing LDV propulsion GHG intensity); and
  • Increasing the vehicle occupancy rate; decreasing the mean per-trip distance; and reducing the per capita trip rate (together representing per capita LDV transport use).

In surveying 2007 LDV usage and fuel economy in an economically diverse set of countries, the team found that the large differences in per capita LDV GHG emissions—which range from ~100–4,000 kg CO2-eq yr-1—are principally explained by differing national per capita LDV use (range: 300–13,000 VKT (vehicle kilometers travelled) yr-1), rather than by fleet average fuel efficiency and carbon intensity factors, which reflect broadly similar car technology worldwide.

They found that in upper-income countries, intensive LDV use results in present-day emissions that exceed the 2050 target per capita range of 50–100 kg CO2-eq yr-1 by a factor of 10–80.

With global per capita LDV use of 10 000 km yr.1, GHG propulsion intensity would need to decline from current levels of around 300 g CO2-eq km-1 to around 5–10 g CO2-eq km-1 on a well-to-wheel basis. Such a performance level would require universal deployment of one or more of: electric vehicles (EVs) running on nearly zero-carbon electricity; cellulosic-biofuel-powered vehicles achieving 300 miles per gallon (0.78 L/100 km); or gasoline-fueled vehicles achieving in excess of 1,000 mpg (0.24 L/100 km).

Sager et al. suggest that meeting the 2050 climate targets will be feasible only with global implementation of robust policies to slow the growth rate of LDV VKT in low-income countries, and to reduce VKT in high-income countries. As an example, they note that by converging global 2050 per capita LDV VKT at levels currently typical of middle-income countries such as Mexico (~3000 km yr-1), a per capita LDV GHG target of 100 kg CO2-eq yr-1 could be met with medium-term technologies, such as 100 mpg (2.35 L/100 km) plug-in hybrid electric cars fueled on a mix of cellulosic biofuels and low-carbon grid electricity.

That particular strategy would require reducing cumulative growth in kilometers travelled to 60%, against the baseline projections of a 100% increase; and would require load factor convergence to around 1.65 persons per vehicle, typical of European averages in 2000.

“ While likely challenging, such efforts would not imply privation.”
—Sager et al.

Achieving such a reduction in LDV VKT could be achieved by coordinated policies, the authors suggest—e.g., reducing average trip length and frequency by ~33% each while increasing the average load factor from ~1.5 to ~2 people per vehicle would be sufficient for the goal.

We have quantified the need for complementary policies required to achieve global climate targets in the light-duty vehicle sector. A truly unified framework would also account for freight interactions, technological options for mass transit, electricity sector emissions, and life-cycle assessments of LDVs and infrastructure. It would also explore in greater detail the substantial co-benefits of lower LDV usage by assessing, for instance, reductions in urban air pollution.

It is crucial to develop the institutional capacity for this effort; to share tailored policy implications with national, regional, and local governments across the world; and to establish standardized data collection mechanisms necessary for global policy evaluation.

—Sager et al.


  • Jalel Sager et al. (2011) Reduce growth rate of light-duty vehicle travel to meet 2050 global climate goals. Environ. Res. Lett. 6 024018 doi: 10.1088/1748-9326/6/2/024018



Other polluters such as coal fired and NG power plants etc would also have to reduce their CO2 foot print.

Nick Lyons

Denser/smarter land use.
Better public transit.
More bicycles, walking.
Livable cities, in other words.


IGCC cuts coal pollution, runs more efficiently and can make fuels from coal, natural gas and biomass to reduce oil imports. Several gains from one move.


Pollution from coal is still 40+% of total and increasing world wide.

Pollution from NG and specially SG is increasing rapidly.

Pollution from alternative fuels is multiplying.

Pollution from tar sands has also multiplied.

Pollution from our vehicle fleets is just as bad as it was and approaching 40% of total.

We are not doing as well as we think/say we are.


I do not worry as much about GHG as I do imported oil from the middle east and OPEC. If Saudi Arabia falls in a revolution the world could see 10 million barrels of oil not on the market every day, our SPR will not last long and we will not have those fuel plants.


I worry the most about cutting edge technological process being kept back due to corporate patent/standard/coordination fighting within the industry players (e.g. plug-in interface tech, subscription models with utilities, etc.). Its unbelievable how much tech at all levels, source, delivery, auto/home/infrastructure due to corporate and to some lesser degree, government political nonsense, is being held up. The lab and scale-up business models are ready to roll out - its the lawyers and accountants gumming it up. And behavior modification is not the way - technology and a risk-toleratnt attitude is. An over-regulated society is a subdued society is a non-innovative society is a retreating and self-destructive society. Tech - the cause of, but more so, the solution to all problems and improvement of society - forget it not.


It is more the lack of capital availability. Venture capitalists now want companies to be seeded and profitable to even look at them, that is not venture capital.


Jer has very good points. Patent rights over protection is a real road block to accelerated technical evolution. All out speculation (and lobbies) is another major road block. Since they are all getting stronger, you can expect an on-going relative slow down of the US economy.

The country (s) that can limit patent rights, lobbies and speculators will take the lead position.


These "Reaserchers" haven't heard about the latest reports that the globe is headed for a mini ice age because the sun is going through a quiet period in sun spot activity.

No the sky is not falling.


I made a short post last year somewhat addressing this issue, and suggested that the limited range of EV's might actually be a good thing.
Ultimately we will at some point need to face the reality that there are simply too many people on the planet and start making adjustments, one way or another. It will probably get very ugly.


I think the most likely future is the us going down all the lines of h2 bev bio and then some while replacing all the nat gas powerplants with advanced models MJUCH more eff then older ones.. converting all old nuke plants into safer new more powerful ones.. and converting all coal plants into co2 capture h2 generating powerplants.. likely of even higher base output then the plants they replace.

This combined with a good solid natural disaster or 3 should handle most pof our needs to prep for 2050-2100.

The real question is china and india.. what happens with them? China is already showing signs of disasterous issues and india is in DEEP poo over water issues as well as other issues...

Even if the us turned into a bowl of jello today the planet would still be headed exactly where its headed now...


Heaven help us (and the planet) if China-India-Brazil-Indonesia-Russia etc) dare to use (waste) as much energy and pollute as much (per capita) as we so proudly learned to do.


It is said if the rest of the world consumed like the U.S. we would need two plants for resources and we only have one.


Fortunately, we will all learn how to live very well with a lot less fossil fuels and pollute 4+ times less per capita. That way, the planet will support up to 15 billion or so. However, it would be wise to do it soon become the majority catch our bad wasteful ways.


Harvey is right, we DO need to use less with behavior, efficiency and technology. When a Tahoe hybrid gets 20 mpg around town instead of 14 mpg, that is good but we need to ask if we really need a Tahoe to go get groceries in the first place.


All this because those flower children progeny at Berkeley don't like pickup trucks?

IGCC cuts coal pollution, runs more efficiently
Actually, IGCC is slightly less efficient than ultrasupercritical steam (the oxygen plant is overhead that PCC doesn't have). OTOH, IGCC's gas cleanup can easily be much better than PCC and also recover much of the CO2 from the gasifier ready for sequestration (or enhanced oil recovery). Recovery of ammonia from the gasifier (for fertilizer) may be another revenue stream.

One thing IGCC does not do is reduce the pollution from coal mining.

and can make fuels from coal, natural gas and biomass to reduce oil imports.
The potential for this is far less than you think, due to the losses in production of liquid fuels, the limitations on expansion of coal mining and the inefficiency of the ICE. We're better off going electric.

Jerry John

In China, there is a certain desire to construct a distinct modernity, one that includes aspects of Chinese tradition. This is true for most places on earth.
china manufacturing

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