US alternative fuel bus transport

The category /transport/bus/generic/ipcc/us contains data on greenhouse gas emissions associated with alternatively-fuelled (ethanol, cng) US buses, sourced from the IPCC Guidelines for National Greenhouse Gas Inventories.

The IPCC methodology for greenhouse gas emissions associated with 'mobile combustion' recommend calculating CO₂ emissions on the basis of fuel consumed, whereas those of CH₄ and N₂O vary more directly with other factors such as vehicle type, emissions control standards, and distance travelled. Therefore, this category provide a number of options for calculating bus-associated greenhouse gas emissions, depending on which combination of fuel consumption, fuel efficiency and distance are specified.

To use this category, set the vehicle fuel type using the fuel drill option. Users can then choose between specifying only fuel consumption, or both fuel consumption ''and'' distances travelled.

Specifying fuel used only

Set the volume of fuel consumed using the fuelConsumed profile item value. If required, the occupancy of the vehicle can be specified so that total vehicular emissions are only shared amongst those passengers under consideration. In order to allocate emissions to a specific number of passengers, the total bus occupancy must be set via the totalOccupancy profile item value and the number of passengers under consideration specified using the accountedPassengers profile item value. If neither of these values is specified, Discover returns a value for emissions attributable to the entire vehicle. Otherwise the returned amount represents CO₂ emissions associated with that volume of fuel shared amongst all accountable passengers.

Specifying fuel used and distance travelled

If both fuel consumed and distance travelled are specified, Discover can use the IPCC methodology to calculate both CO₂ and non-CO₂ (i.e. CH₄ and N₂O) emissions, and therefore the returned value represents CO₂e emissions (i.e. total greenhouse gas emissions expressed as the quantity of CO₂ which would produce the same global warming effect).

If specifying values for distance and fuel consumption, both the distance travelled and the fuel consumed can be specified in a number of different ways, as described below. In any case, the occupancy of the vehicle can be specified so that total vehicular emissions are only shared amongst those passengers under consideration (See Specifying fuel used only for further details on specifying occupancy).

Setting the fuel consumed

To set the fuel consumed, users can specify the volume using the fuelConsumed profile item value. Alternatively, users can specify the rate at which their vehicle consumes fuel using the fuelEfficiency profile item value. In this case, Discover calcuates the total fuel used from this 'efficiency' value together with the value for distance travelled (see below). CO₂ emissions are based on this fuel consumption, while non-CO₂ emissions are calculated directly from the distance travelled.

Setting the distance travelled

To set the distance travelled users may specify a total distance using the distance profile item value. Alternatively, users can specify a number of journeys of some fixed or average distance, by setting the distancePerJourney and numberOfJourneys profile item values. The total distance will then be calculated from these two profile item values.

If a specific number of journeys is taken on a regular basis, users can additionally choose to specify a frequency interval associated with the numberOfJourneys profile item value by specifying one of the following options using the frequency profile item value:

• 'daily'

• 'weekly'

• 'monthly'