Travelfootprint FAQ
Q1 What is the Travelfootprint website designed to do?
The Travelfootprint tool is a Clear Zones project that is intended for use by the general public, business users and policy makers to compare the life cycle environmental impacts of the main methods of passenger travel in the UK. The aim of the site is to inform people of the least polluting forms of transport and encourage: the use of the most sustainable methods for passenger journeys, the purchase of the least polluting vehicles, and to help businesses understand the environmental impact of their fleet and stimulate improvements.
Q2 What do the three Travelfootprint tools actually do?
The Journey Emissions Calculator estimates the emissions of carbon dioxide (CO2), nitrogen oxides (NOx), and particulates generated by a journey in the UK. The Vehicle Emissions Calculator estimates the emissions of carbon dioxide (CO2), nitrogen oxides (NOx), and particulates generated by cars (since 2001). The Fleet Emissions Audit Tool calculate emissions of carbon dioxide (CO2) generated by fleet use of diesel, petrol, LPG and electricity.
Q3 What source data does Travelfootprint use to calculate emissions?
As many comparative studies have done before, the analysis includes an assessment of the environmental impacts associated with the fuel cycle (primary production, extraction, transportation, refining, and vehicle operation) for each of the modes includes in the tool. Unlike previous UK studies, the analysis also assesses the impacts associated with the vehicle cycle (vehicle manufacture, assembly and disposal).
Q4 What source data does Travelfootprint use to calculate emissions?
For car emissions, estimates are based on standardised test cycle emissions data as supplied by the Vehicle Certification Agency (VCA) - http://www.vcacarfueldata.org.uk/. Environmental impact rating methodology is based on ‘external cost’ data as originally published by the EU Cleaner Drive program. For non-car modes, emissions data are taken from a number of sources – see http://www.travelfootprint.org/method for details. To check emissions data where at all possible, the modal CO2 emission data has been compared with the Passenger Transport Emission Factors Report (Methodology Paper) published by DEFRA in 2007
Q5 What are 'vehicle emissions'?
'Vehicle emissions' are those produced solely during vehicle use and exclude those generated during fuel and vehicle production. Vehicle emissions are sometimes called 'tailpipe' or 'exhaust' emissions. For example, vehicle CO2 emissions are those carbon dioxide emissions that are generated during vehicle operation, and are emitted from the vehicle's exhaust pipe.
Q6 What are ‘upstream emissions’?
'Upstream emissions' are those generated during fuel and vehicle production. In other words, emissions are produced in getting the fuel (petrol, diesel, electricity, etc) to the fuel station, and in manufacturing and assembling a vehicle (or any type).
Q7 What does 'lifecycle' mean?
A Life Cycle Analysis (LCA) includes 'whole life' emissions and impacts. Therefore, lifecycle emissions are the sum of vehicle and upstream emissions. For vehicles, this means that emissions produced during fuel and vehicle production are analysed in addition to those produced during vehicle operation.
Q8 What is 'Climate Change'?
By reflecting more heat back to the Earth’s surface, emissions of ‘greenhouse gases’ are leading to the slow but steady increase of the world’s average temperature. The emissions analysis assesses the life cycle impacts of three greenhouse gases associated with transport: carbon dioxide, methane and nitrous oxide.
Q9 What is 'Air Quality'?
Pollutants generated by transport use can be detrimental to air quality and human health. The emissions analysis assesses the life cycle impacts of four regulated emissions associated with transport: carbon monoxide, hydrocarbons, nitrogen oxides and particulates. The analysis also quantifies the impacts of sulphur dioxide.
Q10 What is the ‘Overall Environmental Impact'?
The overall environmental impact represents the combined greenhouse gas and air quality impacts. These are combined using a 70:30 weighting in favour of greenhouse gases. The life cycle overall impact is scored out of 100, the lower the score, the lower the impact on air quality. A score of 100 represents the overall emissions of a highly polluting vehicle.
Q11 Which Environmental Impact score represents the lowest impact?
Zero (0) represents zero environmental impact. As the score(s) increases so does (do) the environmental impact(s). A score of 100 represents a highly polluting vehicle - and is in fact modelled on a car with CO2 emissions of 300g/km with high regulated pollutant emissions.
Q12 Is it possible to have a score greater than 100?
In principle, yes. The calculations used by the analysis do occasionally give a score greater than 100 for vehicles that are highly polluting. However, for simplicity and ease-of-use, the scores for these vehicles is given as 100, the maximum score.
