The Department for Transport does not, at present, hold information on the carbon dioxide emissions of motorcycles broken down in this way. There is currently no statutory requirement placed upon manufacturers to measure the carbon dioxide emissions of new models of motorcycle when they are approved. However, a legislative proposal from the European Commission mandating this measurement has been awaited for some time and is currently expected to be published early in 2009.
A limited amount of data categorised against engine size have been gathered, in the past, in research projects conducted by the Department and the European Commission's Joint Research Centre. The results of these are available on the Department's website and within the Passenger Transport Emissions Factors on DEFRA's website: