Euro 3 bus can be cleaner than Euro 5 hybrid – Ricardo study28 November 2014

A study by Ricardo has revealed that a Euro 3 bus, retrofitted with exhaust emissions after-treatment systems, can produce substantially lower emissions than even a Euro 5 hybrid vehicle.

The study was a follow up to a research project earlier this year, examining the emissions of Euro 4, Euro 5 conventional and Euro 5 hybrid buses operating through a known pollution hot spot in Brighton city centre. This project demonstrated how traffic flow improvement can lower NOx emissions.

In its latest study, however, Ricardo looked at an older Euro 3 bus, retrofitted with a selective catalytic reduction (SCR) and continuously regenerating particulate trap system.

The test was carried out on the same route, and the bus was fitted with Horiba's portable emissions monitoring equipment and filled with ballast to represent a 70% passenger load.

When averaged across the route – and also for the section through the North Street pollution hot spot – the total emissions of the Euro 3 bus were substantially lower than for all vehicles tested.

Data also indicated that, of the nitrogen oxides remaining in the exhaust, the NO2 fraction was substantially lowered to below 10% of total NOx.

Worth noting, however, is that the after-treatment system on this Euro 3 trial bus needed a warm-up period of five to 10 minutes before full emissions control functionality could be achieved.

This, warns Ricardo, may have implications for bus operators with depots in, or close to, low emissions zones.

"The results of this additional study challenges the received wisdom that newer vehicles are always better in terms of their emissions," commnts Jon Andersson, Ricardo's manager of after-treatment and chemical analyses.

"While there is some scope for improvement of the installed system, the Euro 3 retrofit bus equipped with SCR and continuously regenerating particulate trap, produced significantly lower NOx emissions than all other vehicles tested, including a Euro 5 hybrid.

For bus operators looking to balance fleet replacement cycles with the need to reduce pollution, he adds, "the optimal use of retrofit clean technologies of this nature may be an attractive and highly effective alternative to early replacement of older vehicles".

Author
Laura Cork

Related Companies
Eminox Ltd
Horiba UK Ltd
Ricardo UK Ltd

This material is protected by MA Business copyright
See Terms and Conditions.
One-off usage is permitted but bulk copying is not.
For multiple copies contact the sales team.