Guidance on the Environmental Aspects of Vehicle Purchasing
- Environmental Impacts
- Petrol vs Diesel vs LPG
- Vehicle Emission Data
- Emissions Standards
- Alternative Technologies
- Vehicle Excise Duty
- Green Label
- Other measures to reduce emissions
According to the Department for Transport, the transport sector produces about one quarter of the UK’s total emissions of carbon dioxide (CO2), the main greenhouse gas. Road transport contributes 85% of this, with passenger cars accounting for around one half of all carbon emitted by the transport sector. For this reason, low-carbon vehicles and fuels offer opportunities to radically reduce the environmental impact of road transport – both locally in terms of reduced air pollution emissions and lower noise and globally in terms of climate change.
When considering the choice of vehicle, there are a number of key environmental impacts that need to be taken into consideration:
- Resource Depletion. The greater the fuel-efficiency, the less non-renewable resources (oil) will be consumed.
- Global Warming. All fuels produce Carbon Dioxide (CO2) when burnt. This is a greenhouse gas, which contributes to global warming (climate change).
- Local Air Quality. In urban areas, a range of other pollutants associated with exhaust emissions become more significant due to their effects on human health (e.g. asthma and other respiratory illnesses) and damage to buildings and ecology. These pollutants include:
|Exhaust Constituent||Nature and Effects|
|Nitrogen (N2)||No adverse effects|
|Oxygen (O2)||No adverse affects|
|Water (H2O)||No adverse affects|
|Carbon Dioxide (CO2)||Non-toxic gas, but contributes to climate change.|
|Carbon Monoxide (CO)||Results from incomplete combustion of fuel. CO reduces the ability of blood to carry oxygen and can cause headaches, respiratory problems and, at high concentrations, even death.|
|Oxides of Nitrogen (NOx)||Produced in any combustion process. NOx emissions are oxidised in the atmosphere and contribute to acid rain. They also react with hydrocarbons to produce photochemical oxidants, which can harm plants and animals.|
|Sulphur Dioxide (SO2)||Sulphur occurs naturally in the crude oil from which petrol and diesel are refined. It forms acids on combustion leading to acid rain and engine corrosion. It also contributes to the formation of ozone and of particulate matter. Sulphur can also adversely affect the performance of catalytic converters.|
|Hydrocarbons (HC)||HCs are emitted from vehicle exhausts as unburnt fuel and also through evaporation from the fuel tank, from the nozzle when you fill up and also at stages through the fuel supply chain. They react with NOx in sunlight to produce photochemical oxidants (including ozone), which irritate the eyes and throat.|
|Benzene (C6H6)||Naturally occurring in small quantities (less than 2%) in petrol and diesel, Benzene is emitted from vehicle exhausts as unburnt fuel and also through evaporation from the fuel system. Benzene is toxic and carcinogenic. Long-term exposure has been linked with leukaemia.|
|Lead (Pb)||Lead accumulates in body systems and is known to interfere with the normal production of red blood cells. Following the introduction of unleaded petrol and withdrawal of leaded petrol lead is essentially eliminated as an exhaust product.|
|Particulates (PM)||Particulate matter is partly burned fuel associated mainly with diesel engines. PM10s are very small particles that can pass deep into the lungs causing respiratory complaints.|
Although there are a wide variety of fuels and emerging technologies, there are only three main fuels that are currently widely available enough to cater for all driving situations: Petrol, Diesel and LPG (Liquid Propane Gas).
There is no clear argument in favour of any of these three fuels, as each has its own particular advantages and disadvantages.
Petrol engines are less efficient than diesel engines and therefore contribute more to the depletion of non-renewable resources. They also have higher CO2, CO and HC emissions than diesel. However, petrol engines produce less NOx, SO2 and particulates than diesels.
Catalysts can remove a large proportion of the contaminants associated with petrol and diesel engines but they tend to be ineffective until they are properly warmed up, which often doesn‘t happen during short journeys, which are typical of the majority of journeys in and around the University. LPG has lower CO and CO2 emissions than petrol, but higher NOx emissions. In comparison with diesel, LPG has lower emissions of NOx and particulates but higher emissions of CO and HC. LPG is cheaper than petrol and diesel due to reduced levels of taxation, and fuel costs are typically around 40% less than petrol or diesel cars. However they require an additional fuel tank which can increase the weight of the car and decrease the fuel-efficiency and take up boot space. The conversion cost is around £1,000-2,000. Converted vehicles retain the ability to run on petrol if they are unable to refill with LPG. The government Powershift grant to assist with conversion costs to LPG is no longer available, which means that the added cost of conversion off-sets some of the reduced running costs. LPG is currently used in UMS vans and is available from the City Council transport depot in Mill Road.
The Department of Health (COMEAP, 1999) guidance states that ‘...definitive advice as to the preferability, on health grounds, of diesel vs petrol-powered light vehicles is not possible. However, concerns about the effects of particles on health in urban areas currently tip the balance in favour of petrol’. Also, Friends of the Earth does not recommend diesel for cars that are predominantly used for driving in towns.
Whichever category of fuel is chosen, it would be best to choose a vehicle with the lowest possible emissions. Comprehensive guidance on CO2 emissions for all new vehicles can be obtained from the Vehicle Certification Agency.
Before passenger cars can be type approved for sale in the European Union they must meet certain standards for exhaust emissions. All new car models are subject to a series of legally enforced technical tests to ensure that they meet minimum laid-down standards. These ‘type approval’ tests include standards for exhaust emissions that have been getting progressively more stringent since the early 1990s.
New cars currently have to meet the Euro 4 standard though there are some that already meet the more exacting Euro 5 & 6 standards.
Vehicle emissions standards, however, differ between Light and Heavy Duty Vehicles. For Light Duty Vehicles, such as passenger cars, the stages are known as Euro 1 (1993), Euro 2 (1996), Euro 3 (2000), Euro 4 (2005), Euro 5 (2009), and Euro 6 (2014). Heavy Duty Vehicle emissions standards use Roman numerals to notate stages.
For more information on the Euro vehicle emissions standards visit: http://europa.eu/scadplus/leg/en/lvb/l28186.htm.
There are a number of alternative vehicle/fuel technologies that are starting to become more readily available, including Electric Cars, Fuel Cells, Biodiesel, Compressed Natural Gas (CNG) and Hybrid Cars (which use a combination of petrol /diesel engine coupled to an electric motor) The most promising of these in the short-term is likely to be an electric car, e.g. G-Wiz (see the GoinGreen website for more information about G-Wiz), which could be used for short journeys in and around Cambridge.
Electric cars do not emit any pollutants at all during operation, although recharging the batteries can lead to the production of CO2 emissions associated with electricity generation. However as the University currently obtains 99% of its electricity requirements from carbon-emission free sources (Hydro and Renewables) this would not be the case whilst the current electricity supply contract arrangements remains in force.
Lower emission cars also have the added benefit of reduced Vehicle Excise Duty (Road Tax). This benefit has and will continue to become even greater as the government phases in the new tax bands outlined in the Budget 2008. The Budget, which reclassified vehicles according to the levels of carbon they emit, will introduce a new system and higher payment levels to the Vehicle Excise Duty. In fact, starting next year, high emission cars will face a hefty “showroom tax” payable during the first year of purchase, as seen below.
|Up to 100||0||A||Honda Insight petrol-electric hybrid|
|101-120||£35||B||Toyota Prius 1.5 petrol-electric hybrid|
|121-150||£120||C||Fiat Panda 1.2 petrol|
|151-165||£145||D||Peugeot 307 1.4 petrol|
|166-185||£170||E||Ford Mondeo saloon 1.8i petrol|
|186-225||£210||F||BMW 5 series estate 3.0 diesel|
|226+||£400||G||Range Rover 4.4 V8 petrol auto|
New System (from April 2009)
|CO2 (g/km)||Tax (2009-10)||Tax (2010-11)||Band||Example|
|First Year Rate||Standard Rate|
|Up to 100||0||0||0||A||VW Polo Bluemotion 1.4 Tdi|
|101-110||£20||0*||£20||B||Skoda Fabia Estate Greenline|
|111-120||£30||0*||£35||C||Mazda 2 1.4|
|121-130||£90||0*||£95||D||Kia Picanto 1.1|
|131-140||£110||£115||£115||E||Renault Clio 1.2 Quickshift|
|141-150||£120||£125||£125||F||Vauxhall Astra 1.4 16V|
|151-160||£150||£155||£155||G||Audi A3 2.0 Tdi|
|161-170||£175||£250+||£180||H||Citroen C5 2.2 Hdi Est|
|171-180||£205||£300+||£210||I||Ford Mondeo 1.6 Estate|
|181-200||£260||£425+||£270||J||Saab 9-3 Estate|
|201-225||£300||£550+||£310||K||Peugeot 407 saloon 2.0 Auto|
|226-255||£415||£750+||£430||L||Peugeot 807 2.0 Auto|
|255+||£440||£950+||£455||M||Land Rover Sport Auto 3.6 TDV8|
*Tax exempt for First Year
+Total includes first year showroom tax
The Vehicle Certification Agency (VCA) has introduced new colour-coded label to help with the identification of low-emission cars. The label is based on the A to F ‘Vehicle Excise Duty’ CO2 bands similar to the existing energy rating label for domestic goods, such as refrigerators.
For more information see the VCA website:
While a vehicle’s make, model, and fuel type significantly impacts the amount of carbon it emits, the driver is important as well. By modifying driver behaviour, the driver can help to reduce vehicle emissions. Ways in which to do this include:
- Regular servicing – this helps keep the engine at best efficiency
- Making sure the tyres are inflated to the correct pressure for the vehicle
- Using the correct specification of engine oil
- Planning ahead – choose uncongested routes, combine trips, or car share
- Don’t carry unnecessary weight
- Streamlining – Roof racks/boxes create extra wind resistance and so increase fuel consumption. If you don‘t need it take it off, if you do, pack carefully to reduce the extra drag
- Driving off as soon as possible after starting
- Driving smoothly – sharp acceleration and heavy braking increases fuel consumption
- Driving at or within the speed limit – the faster you go the greater the fuel consumption and the greater the pollution too.
- Changing gear as soon as possible without laboring the engine – try changing up at an engine speed of around 2000 rpm in a diesel car or around 2500 rpm in a petrol car. This can make such a difference to fuel consumption that all cars in the future are likely to be fitted with Gear Shift indicators that light a lamp on the dashboard to indicate the most efficient gear change points.
- Rolling – If you can keep the car moving all the time, so much the better. Stopping then starting again uses more fuel than keeping rolling.
- Avoiding idle – If you do get caught in a queue avoid wasting fuel by turning the engine off if it looks like you could be waiting for more than three minutes.
- Turning off extra electrical equipment (i.e. heated rear windscreen, demister blowers and headlights) when you don‘t need them.
Of course, the best way to reduce emissions is not to use a car at all, but to use public transport or walk or cycle wherever possible.
The most attractive option in terms of environmental performance and running costs is for LPG / Petrol dual fuel vehicles.
Where LPG is not viable, it would be advisable to have a mixture of diesel and petrol cars to enable staff to select the one most appropriate to the journey involved, given the competing priorities surrounding the conflict between CO2 emissions (Global Warming) and other pollutants (Local Air Quality).
In general, petrol cars would be better for short journeys in and around Cambridge where local air quality considerations are paramount. Diesel cars would be better for longer journeys where fuel efficiency and CO2 emissions are more important.
Any new vehicles should meet least Euro IV emission standard and preferably the Euro V standard. Consideration should also be given to exploring the feasibility of alternative powered vehicles, particularly electric powered cars for journeys in and around the city centre.
European Federation for Transport & Environment
Transport for London: Congestion Charging
Transport for London: Low Emission Zone
Cambridgeshire County Council: Transport & Streets
Department for Transport
DfT: Cleaner Vehicles Task Force
Energy Saving Trust
Vehicle Certification Agency
Direct Gov: Motoring
Environmental Transport Association
Car Clubs: Pay As You Go
European Mobility Week
The Green Fuel Company
Alternative Fuels Refuelling Map
Travel for Work
Low Carbon Vehicle Partnership
CO2 Car Rankings
Car Maintenance How-to
Online Journey Planner