Green Travel Data

How we calculate the per-passenger emissions of a car journey

Using the per-km well-to-tank emissions of an average car from the Government conversion factors for company reporting of greenhouse gas emissions, which is 0.2099 kgCO2e/km (2026 figures) for an average car with unknown fuel type (average of petrol, diesel, hybrid and battery based on relevant proportions of each). Car occupancy is based on the average of 1.6 passengers per car. Distances are based on the shortest road distance between the two points from an open-source journey routing tool, with 10% added for diversions due to traffic rerouting and congestion.

How we calculate the per-passenger emissions of an air journey

Using the per-km well-to-tank emissions of a domestic flight from the Government conversion factors, which is 0.26278 kgCO2e/km (2026 figures) for a domestic aircraft of average passenger load. Distances for air journeys are based on the rail distance between the two stations and are therefore indicative of the equivalent air emissions of a journey of the same length. Air comparisons are only provided for rail journeys of more than 150km, the minimum viable distance for an air journey.

How we calculate the saving in cups of water

The emissions created by generating enough energy to boil one cup of water is 0.00619 kgCO2e. The difference between a rail and a car/air journey is divided by this figure to calculate the saving in cups of water.