Go with the flow – Brighton bus emissions study reveals findings 23 July 2014
Early results of a research project to evaluate in-service bus emissions in Brighton have revealed that smoothing traffic flow could significantly reduce vehicle emissions.
The study, by the Brighton & Hove Bus and Coach Company, Ricardo and test equipment supplier Horiba, looked at the emissions of a cross-section of the operator's 280-strong bus fleet operating on a central Brighton route.
Tests were carried out on a Euro 4 vehicle fitted with EGR (exhaust gas recirculation) emissions reduction technology, a Euro 5 vehicle fitted with SCR (selective catalytic reduction) after-treatment, and another Euro 5 SCR equipped diesel-electric hybrid vehicle.
Each bus was fitted with Horiba's Portable Emissions Monitoring System (PEMS) equipment and artificially loaded with ballast representing a 70% passenger load.
The vehicles were tested on multiple trips and in normal traffic, stopping at regular bus stops in a similar manner to the normal passenger service. Different drivers and driving styles were used in one of the three vehicles, so that the effects of these variables could also be assessed.
Real-time measurements were taken of each vehicle's CO2 and NOx emissions. Estimates were also made of the proportion of NOx emitted as NO2. The information was correlated with GPS measurements to give an accurate analysis of the effects of route topology.
Details of the test route showed that poor traffic flow on a westbound route was a key contributor to higher NOx emissions, due to erratic stop-start operation on the uphill section.
The study concluded that initiatives aimed at smoothing traffic flow at this location, and allowing buses to operate without unnecessarily frequent stop-start cycles, could have a significant positive impact on both NOx emissions and fuel economy.
The results were handed to Brighton & Hove City Council earlier this month and will help to shape its traffic improvement policies.
Horiba UK Ltd
Ricardo UK Ltd
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