Making direct comparisons between these types of transport is not straightforward because of the range of factors that impact on fuel efficiency; for example, the size of the vehicle or how heavily laden it is. However, an assessment has been made of the carbon dioxide (CO2) efficiency of transporting freight by road, rail and other methods. This forms part of the ‘Guidelines for Company Reporting on Greenhouse Gas Emissions’, published by DEFRA, to assist companies in reporting their carbon emissions. Emissions for freight carried by road (table 1) are based on how full the vehicle is, and conversion factors for CO2 emissions per tonne kilometre are provided for rail (table 2) and other freight transport types. It is possible to calculate CO2 emissions from transporting a certain amount of freight by road or rail from these data.
Diesel freight road mileage conversion factors Type of lorry Percentage weight laden Total km travelled x litres fuel per km x Fuel conversion factor Total kg C02 Rigid 0 x 0.236 x 2.63 25 x 0.262 x 2.63 50 x 0.288 x 2.63 75 x 0.314 x 2.63 100 x 0.340 x 2.63 Articulated 0 x 0.311 x 2.63 25 x 0.345 x 2.63 50 x 0.379 x 2.63 75 x 0.414 x 2.63 100 x 0.448 x 2.63
Other freight transport mileage conversion factors Freight transport mode Tonne km x Factor Total kg CO2 Rail x 0.03 Air long haul x 0.57 short haul x 1.58 Shipping small roll on-roll off x 0.06 large roll on-roll off x 0.02 small tanker x 0.04 large tanker x 0.003 small bulk carrier x 0.014 large bulk carrier x 0.007
Further details are available on the DEFRA website. The guidelines are currently being updated and are scheduled to be published soon.