Picture by carrib under the Creative Commons License

Here at Zoombu we are all keen travellers and want to minimise the impact of our travels on the environment. That’s why we’ve incorporated carbon footprint as a key parameter of our journey search results. When you search for a trip with Zoombu, we tell you the end-to-end carbon footprint associated with a particular route and help you to choose a route that minimises your environmental impact. Since we realise that it’s not always practical to consider carbon footprint in isolation, our search results help you to understand the trade-off between carbon footprint, the cost and the duration of the end-to-end trip, to help you make the best overall choice.

Calculating the carbon footprint associated with a route involves a number of steps:

Firstly we determine the carbon emissions coefficient (carbon dioxide per passenger km) associated with a particular mode of transportation and vehicle type. We use approved coefficients sourced from the Department for Transport and we source some specific coefficients directly from transportation providers (many of whom have performed detailed emissions studies on specific vehicle types and routes). Consistency between providers and modes of transport is very important and we do our best to ensure that the basis for all emissions coefficient data we use is common.

Secondly we calculate the distance of travel of each route segment as closely as possible to the real distance.  We use some approximations for train journeys to account for average track curvature and for flight paths to account for deviation from a ‘great circle’ path and average circulation distance.

Finally we multiply the specific emissions coefficients by the distance for each segment of the route and sum to present the overall carbon footprint measure.

We are constantly seeking to improve the carbon footprint data that we present for our routes. We are working with transportation providers to ensure we know more about specific vehicle types use corresponding emissions coefficients. Furthermore, if you choose driving as part of your route, we currently estimate the emissions associated with an average car, and in future versions of Zoombu we will let you find and store emissions data for your car. Finally, in common with most measures of carbon footprint, we currently display data for only carbon dioxide emissions. In the future data about other types of emissions is likely to be more reliable and when it is we will include these in our results.

We’re always keen for feedback on this topic and to work with other organisations seeking to provide carbon footprint measurements, so please get in touch if you have questions or think you can contribute!

- Posted by Rachel