This study measured the major health-related pollutants in six different train types on five separate journeys, 30 journeys in all. These trains represent a range of rolling stock, both diesel and bimodal, old and new. 

Key Findings 

The levels of health-related pollutants and the exposure of the passengers were found to vary depending on the train type, the location of the exhaust, the track gradient and whether the train was in a tunnel. High levels of all pollutants were found during time spent in stations and tunnels. 

The key points are: 

• Air quality on board trains was different along the different routes. 
• The highest levels of particles were found on the journey between London Euston and Birmingham New Street on the Class 221 trains. These levels were significantly higher than typical levels routinely measured at busy urban roadside locations. 

• The highest levels of nitrogen dioxide were found between Paddington to Bristol Temple Meads, on board a Class 800 bi-mode train when in diesel mode. These levels were also significantly higher than typical levels routinely measured at busy urban roadside locations. 
• There was a large difference in measured nitrogen dioxide when comparing diesel mode to electric mode on both the Class 800 and Class 755 train. 
• Newer train types do not necessarily have better on-board air quality compared to older trains. 

Air quality on diesel trains was found to be close to that found when travelling by bus, bicycle or car, but electric and bi-mode trains were cleaner. 

PI: Dr David Green