The category /transport/bus/generic contains passenger-based emissions data relating to bus travel in the UK and the Republic of Ireland. This category provides CO2 emissions only and should be considered to represent a useful first point of entry to bus-related emissions. If users are interested in more specific and comprehensive datasets (which include CO2 as well as CH4 and N2O emissions) they should see the following categories:
To use this category, select they type of bus journey using the type drill parameter. Next, users can specify the country within which travel is undertaken, and then choose between calculations based on absolute travel distances or multiple journeys. The former may be appropriate for single, long-distance journeys (e.g. coach journeys), while the latter is useful for those journeys which are repeated on a regular basis (e.g. commuting).
Setting the country
Emissions factors relating to the UK (sourced from the government agency DEFRA) and the Republic of Ireland are available within this category. To specify the appropriate emissions factor users can set the country parameter to any of the following values:
- 'United Kingdom'
If no value is specified, the UK emissions factors are used by default. If calculations are stored using profiles, the country can be specified within the profile metadata. Users should note, however, that directly specified country parameters override any set as profile metadata.
Calculating by absolute distance
To calculate emissions based on single journey distance, simply set the distance using the distance parameter. Users can additionally set a multiple number of passengers by setting the numberOfPassengers parameter. The value returned represents CO2 emissions attributable to all nominated passengers for the distance travelled.
Calculating by multiple journeys
To calculate emissions based on a number of repeated journeys, users must specify (1) a journey distance, and (2) a journey frequency. To set the journey distance, simply set the distance using the distancePerJourney parameter. If the distance is not known, a 'typical' distance can be substituted by setting the useTypicalDistance parameter to 'true'. In these cases, the following distances are used for each of the drill options:
- typical: 7.7 km
- local: 7.7 km
- london: 5.9 km
- coach: 151 km
Journey frequency is expressed in terms of a number of journeys per some specified time period, for example ten journeys per week or one journey per month. The quantity of journeys is specified by setting the numberOfJourneys parameter to a numeric value, while the time period is set using the journeyFrequency parameter. Valid values for the journeyFrequency parameter are as follows:
Users can optionally declare the stated journey frequency to represent return journeys by setting the isReturn parameter to 'true', in which case the total number of journeys are doubled. Additionally, a multiple number of passengers can be included by setting the numberOfPassengers parameter. The value returned represents CO2 emissions attributable to all nominated passengers per year.