Taxi generic Defra

This category is deprecated. The latest DEFRA methodology for taxi transport can be found here and here.

This category allows users to calculate greenhouse gas emissions from taxi journeys either per passenger or per vehicle. The methodology follows the latest Defra emission factors and advice.

To use this category use the drill-down type to select the type of taxi used from the following options.

• typical

• black cab

The distancePerJourney is then required as a profile item value. There are three further optional profile item values: numberOfJourneys, isReturn, numberOfPassengers. To specify multiple journeys, set the number of journeys using the numberOfJourneys profile item value (default of 1), in which case Discover multiplies the distance per journey by the number of journeys to establish the total distance travelled. The isReturn profile item can be set to either true or false ('false' by default), if true the algorithm doubles the numberOfJourneys. The returned value represents greenhouse gas emissions attributable to the entire vehicle, which are based on the 'medium/large diesel' and 'large diesel' cars in the Defra Car category for the typical and black cab drill choices respectively.

To calculate on a per passenger basis, set the numberOfPassengers profile item value to the number of passengers. In this case, typical taxi occupancy data (1.4 for typical taxi and 1.5 for black cab) is used to calculate a per passenger emissions factor which is then multiplied by the number of passengers. The returned value represents greenhouse gases attributable to all passengers for the journey(s) specified.

The user is also able to specify fuel consumption using the optional ownFuelConsumption or totalFuelConsumed profile item values. If the user has a reliable fuel use rate (km/L) this can be entered instead of using the set emission factors in this category. In this case the emission factor from the Fuel_Defra category is divided by the given fuel consumption rate and multiplied by the distance travelled to calculate the emissions for the selected journey. The totalFuelConsumed is to be used if the user knows the amount of fuel used, rather than a distance travelled. In this case the Fuel_Defra category emission factor is simply multiplied by the given total fuel amount to calculate the total emissions for the selected journey.

Algorithm

CO2eEmissionFactor = CO2EF + CO2eEFForN2O + CO2eEFForCH4

CO2e = CO2eEmissionFactor * distancePerJourney * numberOfJourneys * numberOfPassengers

The algorithm returns a value of kgCO₂e for the selected journey. This value includes contributions from carbon dioxide, nitrous oxide and methane.