Bus Emissions Reduction on Putney High Street

Claire Cheriyan, on behalf of Finn Coyle

Principal Analyst (Emissions Modelling and Monitoring)

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Pollution in Putney

Source Apportionment for NOx on Putney High St

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SCR Roll-out

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Route Selection

NO2 Focus Areas

NOx Abatement Retrofit £10 million funding (DfT/TfL) to retrofit approx 1000 Euro III buses with SCR

1015 buses now fitted to 3 types of Euro III bus

NOx reacts with ammonia over the catalyst and reduces it to nitrogen and water

(NO and NO2) + NH3 N2 + H2ON2O + NH3 (Secondary Emissions)

95 out of 220 buses that use Putney High Street were retrofitted with SCR

This made Putney the ideal location for monitoring the effectiveness of SCR programme

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Calculating the effectiveness of SCR• TfL developed with Millbrook a ‘real world’ drive cycle based on Route 159

from Brixton to Oxford Street

• Real World test cycle with representative exhaust temperature essential forSCR development

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SCR Emissions Test Results

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NOx Reduction operating on Putney High Street

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SCRT retrofit

base bus

0.0 2.5 5.0 7.5NO2 (g /kg fuel)

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Remote Sensing on Putney Hill - David Carslaw

• On average we see a 61% reduction in emissions of NO2

• 45% reduction in emissions of NOx

• These reductions are substantial compared with the average performance of the bus fleet in London including OEM SCR systems

SCRT retrofit

base bus

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• Emissions distribution– SCRT buses sometimes behave like 

base buses– Other times there is ~90% 

reduction in NOx

• Test track results– Importance of SCR inlet 

temperature– >200oC gives 90% reduction in NOx

• Expect greater reduction in NOx where engine runs hotter

Monitoring Scheme Effectiveness – Putney High St

“there were 42% and 71% fewer exceedences at the kerb and façade respectively in the second half 

of 2013 when compared to the second half of 2010 to 2012”

“a sustained decrease in ambient NO2 concentrations of 16% (during normalised 

meteorological conditions) at the façade is an encouraging result”

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Putney High St NO2 Monitor Trends

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Summary and Conclusions

• The SCR Retrofit Programme has been successful in reducing NO2 concentrations on Putney High Street

• Euro VI and 3rd Generation SCR systems offer the potential for further savings going forward

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Questions?

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