Air Quality
The operation of our vehicle fleet also gives rise to a range of other combustion gases which can affect local air quality. These include nitrogen oxides, particulates, hydrocarbons and carbon monoxide.
For all our operations in both the UK and North America we calculate these emissions on the basis of engine type and fuel usage using recognised emission factors. For UK Bus, local emission factors are extracted from the National Atmospheric Emissions Inventory. For UK Rail, local emission conversion factors are extracted from conversion of diesel engine exhaust emission data, published by Interfleet Technology, 14 April 2005. In North America we use the USEPA Mobile 6 model.
Legislation in both Europe and North America is progressively tightening emission limits on new vehicles. As we continue to invest in new vehicles our emissions will continue to decrease.
Our UK Bus fleet now comprises 30% EURO III engines and 22% EURO IV and V engines. In the last five years we have achieved the following emission reductions in the UK.
% reduction in local emissions over the past 5 years
| Local Emissions | UK Bus | UK Rail |
|---|---|---|
| Particulates | -45% | -46% |
| Nitrogen Oxides | -27% | -10% |
| Hydrocarbons | -43% | -22% |
| Carbon Monoxide | -37% | -13% |
In North America the model used to calculate emissions was significantly updated in 2010. It is therefore difficult to make direct comparisons with data prior to this point. In addition the vehicle fleet in North America is not static due to the churn of contracts which again makes year on year comparisons difficult.
A full breakdown of our emissions can be found here.
