Summary of CO2 emissions for BAU and Maximum Impact (MI ) scenarios. The MI scenario anticipates complete tailpipe decarbonization of road and rail. Click to enlarge.

The entire UK transport sector could see a 76% reduction in CO2 emissions by 2050 compared with business-as-usual under a Maximum Impact (MI) scenario that applies all feasible interventions to achieve a “near zero

carbon” UK transport sector, according to a new study from researchers at the University of York and the Stockholm Environment Institute (SEI) York. Under the MI Scenario, road and rail are projected to become carbon neutral (rail via 100% electrification).

The recommended measures and assumptions to achieve the MI scenario are grouped into four areas: Spatial planning, Fiscal, Behavioral and Technology. With the first three categories, the report recommends specific policy actions designed to reduce demand or change high-consumption behavior, that in turn, can influence the technology end-points.

The authors note that the 76% reduction falls short of the zero carbon target, due entirely to CO2 emissions from aviation and shipping. However:

…the MI Scenario for road and rail transport depends on the decarbonisation of the electricity supply system. A detailed analysis of policy

pathways leading to such a decarbonised electricity supply in the UK is outside the scope of this study. However, if the electrical power sector decarbonisation

by 2050 is less than 100 per cent, CO2 emissions from

road and rail transport will be substantially higher than

projected for the MI Scenario.

—“Towards a Zero Carbon Vision for UK Transport”

Road transport. The report outlines measures under each of the four main areas to bring road transport CO2 emissions down to zero.

Measures for Spatial Planning include:

  • Pedestrian-oriented design: urban car VKT

    reduced by 10%.

  • Road space reallocation: urban car CO2

    emissions reduced by 11%.

  • High occupancy only vehicle (HOV) lanes:

    urban car VKT reduced by 1.4%.

  • Compact development: for cities >100K

    population, all traffic VKT reduced by 30%.

  • Regional co-operation model for HGVs:

    assume 50% reduction in total VKT.

Fiscal assumptions include:

  • Road user charges resulting in a 3% reduction in all


  • Workplace car parking charges: CO2 emissions

    from commuting by car reduced by 12%. Thus, assuming 25% of

    total car CO2 emissions are due to commuting, this equates to a 3% reduction in total passenger car CO2


  • Urban, non-commuting car parking charges: A 13% reduction in urban car VKT assuming: (a) VKT elasticity factor of -0.07; (b) 75% of car CO2 emissions are for non-commuting purposes assuming that this also applies to urban car use;

    and (c) average parking charges increase in real

    terms by 10% per annum from 2010 to

    2030, to give a 570% final increase.

  • Fuel price: A 5% per annum fuel price

    escalator is introduced from 2010 onwards producing a 600% fuel price increase by

    2050 for all road vehicles. A short-term elasticity

    factor of -0.25 for fuel consumption applied annually results in a 40 per

    cent reduction in CO2 emissions for all fossil

    fuel powered road vehicles by 2050. (An implicit

    assumption here is that there will be progressive

    availability of non-CO2 emitting alternatives such

    as electric vehicles powered by carbon neutral

    electricity, and carbon neutral public transport


  • VED circulation tax: Increased differentiation

    reduces VKT for all cars by 4.8%.

  • Car purchase tax and ‘Feebate’ systems based on

    fuel consumption: Reduces VKT for all cars by 4%.

  • Public transport fares subsidy: a 30%

    reduction in fares will reduce CO2 emissions for

    all cars by 2%.

Requisite Behavioral changes include:

  • Ecological driving: 8% reduction in car

    CO2 emissions.

  • Reducing motorway speed limit to 60 mph and

    enforcing it: 10% reduction in motorway

    CO2 emissions.

  • Car share: reduction in car VKT for urban (8.3%) and rural (3.6%) driving.
  • Modal shift for road freight: 20% reduction

    in CO2 emissions from HGVs.

The assumptions in the MI Technology package differ from the prior three in that they represent desired technology end-points rather than a set of policy prescriptions. The end-points include:

  • All passenger cars, LDVs, motorcycles and

    HGVs/buses less than 12 tonnes in weight to be

    plug-in electric vehicles (PEV) using 100% renewable electricity or

    hydrogen fuel cell powered (using carbon neutral

    sourced hydrogen).

  • Heavier HGVs and buses/coaches (>12 tonnes)

    to be powered by either H2 fuel cells (with carbon

    neutral sourced hydrogen) or sustainable biofuel.

  • Liquefied petroleum gas (LPG) vehicles

    completely phased out.

These technology end-points

could arise simply as a result of the spatial, fiscal and

behavioural measures described earlier. In particular, the

fiscal measures alone may render petrol/diesel powered

vehicles prohibitively expensive compared with say,

PEVs. Alternatively, a society being adversely affected

by climate change in forty years time may reasonably

decide to ban any remaining petrol/diesel vehicles

completely. In this case the technology assumptions

would in a sense, also represent policy interventions.

Of course, significant policy interventions would be

required to produce the carbon neutral UK electricity

power generation sector on which the above assumptions

are based, but a detailed analysis of these is beyond the

scope of this study.

“Towards a Zero Carbon Vision for UK Transport”

The results of this research and the clear policy recommendations have been sent to the Minister of Transport and the Minister responsible for climate change policy, the Chairs of the Regeneration and Transport Board and Environment Board of the Local Government Association, the AA and RAC, the Association of Train Operating Companies, the bus industry, the British Shipping Council, British Airways, Easyjet and Ryanair, BAA and the Freight Transport Association.