2.4  Vehicle Emissions

• In order of importance the three most important greenhouse gases associated with vehicles are:
  
  
• Carbon Dioxide.  
  
  
• Methane.
  
  
• Nitrous Oxide.  
  
  
• Overall emission levels for petrol powered cars are being reduced partly by the increased use of three-way catalytic converters and fuel injection systems. Overall emission levels for diesel vehicles are also being reduced by the development of direct injection engines and diesel particulate filters.
  
  
• Note: Diesel powered cars typically emit about 20% fewer greenhouse gases than petrol powered cars.