The study editor Sir David King (former Chief Scientific Adviser to the UK Government) and lead author Dr. Oliver Inderwildi urge the government to impose higher taxes on drivers of large, inefficient vehicles and reinvest the money in better public transport and measures to get more people cycling and walking.

An new study from the Smith School of Enterprise and the Environment at Oxford University suggests that best way to reduce transport greenhouse gas (GHG) emissions in the short term is a “drastic downscaling of both size and weight” of conventional gasoline and diesel cars.

“The most significant impact that can be made in reducing CO 2 emissions from automobiles in the coming decades is reducing the average weight and engine size of vehicles.” —Future of Mobility Roadmap

The report “Future of Mobility Roadmap” assesses the potential for low carbon transport on land, by air and sea. Among its findings for land transport—the largest contributor to the transport sector’s greenhouse gas emissions—are:

In the short-term, turbocharging and downscaling in combination with weight reduction of current vehicle technology offer a significant opportunity for reductions.

In the medium-term, hybrid systems, those using internal combustion engines and regenerative electric systems such as the Toyota Prius, offer significant savings and will help the evolution to a purely electric drivetrain.

While purely electric vehicles are not zero emission vehicles due to electricity and hydrogen generation they will be important low carbon transport in the long term.

Plug-in electric vehicles are restricted by battery technology, fuel cell systems are limited by power density of the unit and both systems are challenged by limited rare material availability.

First generation biofuels, those derived from food stocks, have proved the viability of such fuels, but remain a localized solution, as in Brazil.

Second generation biofuels synthesized from inedible cellulosic biomass have the potential to be true low carbon fuels but are constrained by land availability.

Algae-based fuel show promise as they exclude land use and food security issues, but they require a mass production break through to be viable.

Both electric and diesel rail systems have low operating emissions but high embedded infrastructural costs and lack route flexibility.

In the short-term a significant impact that can be made in reducing CO 2 emissions from automobiles by blunt down-scaling the physical vehicle size and engine capacity. In the medium-term, alternative powertrain technologies such as HEVs and PHEVs, by combining the advantages of ICEVs and battery electric vehicle (BEV), offer perhaps the best interim step. In the long-term it is envisaged that all electric drive vehicles will be the man source of transportation. These can be split into two distinct groups, fuel cell vehicles (FCV) and BEV.

...As with technology, economic policies also have an important role to play in reducing GHG emissions from transport. An efficient mobility model for the future must take into account the true costs of transport and its regulatory framework needs to create incentives for people to make sustainable transport choices. In order to achieve this economic instruments can be used to correct road transport externalities such as environmental and road damage, accidents, congestion, and oil dependence. CAC [command and control] policies and incentive-based policies can be used to reduce the negative impact of transport externalities. Physical policies, soft policies, and knowledge policies can be used in combination in an integrated framework with taxes and permits in order to move towards a sustainable transport model. —Future of Mobility Roadmap

Myth Busting The report identifies a number of myths surrounding low-carbon road transport: “Diesel cars are highly polluting.” “We should just use fuel cells.” “Electric vehicles are zero-emission.” “Corn ethanol is an environmentally friendly fuel.” “Biofuels compete with food sources.” “Biofuels will save the day.” “Policy X is the only solution.”

Air. For the air sector, the report finds that technical changes, such as improvements to propulsions systems and reduction to aerodynamic drag could reduce emissions by up to 50%, in the short term. However, the rate of uptake of new technologies is restricted by fleet lifetimes.

Longer term developments require change to the current aircraft architecture from “tube and wing” to “flying wing” systems, offering 32% reduction in GHG through drag reduction alone. Biofuels and operational improvements could also reduce the GHG emissions from aviation.

Sea. Sea or maritime transportation accounts for 3% of global GHG emissions while transporting 70% of the world’s cargo by volume, leading to the lowest emission per tonne kilometer of all modes discussed in the report. Through both technical and operational change, reductions of up to 75% of GHG emission are possible in the medium to long term, the authors conclude.

Behavioral Change. The report throughout emphasizes the need for behavioral change to achieve low carbon transport:

Either top-down or bottom-up polices are required.

Top-down methods include command and control polices, such as regulation and incentive based polices, such as taxes and charges.

Top-down methods are not efficient from an economical perspective but are when drastic changes in activity are required.

Bottom up methods or complementary polices can be used in combination with top down methods.

Complementary polices fall into one of three broad categories: physical polices, soft polices and knowledge polices.

Bottom-up methods are economically efficient but do not always achieve their full potential for change.

The study warns that action must be taken immediately to have any impact on climate change because of the long lifetime of transport fleets and subsequent delays in technological impact.

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