Real-time emission tests bring results

PEMS – portable emissions measurement systems – developed by Horiba Automotive has been used in trials in Brighton, UK in conjunction with Ricardo plc, to assess ‘real world’ emissions from three buses, including a diesel-electric hybrid.

PEMS was developed in response to new requirements for exhaust emissions measurement from vehicles being driven on public roads.

In order to provide a cross-section of the Brighton & Hove bus fleet, the tests were carried out on a Euro 1V vehicle with EGR after-treatment technology, a Euro V vehicle fitted with SCR after-treatment, and a further Euro V SCR-equipped diesel-electric hybrid vehicle.

Each bus was instrumented with Horiba’s PEMS equipment and artificially loaded with ballast to represent a 70 per cent passenger load.

For health and safety reasons, passengers were not allowed on the vehicles and tests did not form part of the regular timetable.

Horiba’s equipment was installed on rear seats of the buses adjacent to the engine. In each case, the exhaust system was adapted in the depot prior to tests being carried out on the vehicle.

This enabled the research team to ensure that all the sensors were incorporated in the system inside the vehicle rather than outside the vehicle’s envelope, as is more often the case.

“The installation was complex but it was important that measurements of each vehicle’s emissions of CO2 and NOx were scientifically recorded robustly and in real time,” noted Jon Andersson, Ricardo’s manager of after-treatment and chemical analyses.

Use of the latest PEMS technology requires expert handling and a thorough understanding of vehicle after-treatment technologies, but applied intelligently it can yield an extremely valuable insight into the true emissions of common vehicle types and can help validate potential improvement initiatives, according to Ricardo.

The company added that by considering vehicle technology deployment, operational management, local traffic and transport policy in this holistic yet focused and cost-effective manner, efforts to improve local air quality should be both better informed and more effective.

Results of the research appear to be well aligned with proposals already under discussion by Brighton & Hove City Council to improve bus flow in the vicinity of the known air quality “hot spot”.

Brighton & Hove Bus and Coach Company, part of the Go-Ahead Group plc, operates a fleet of 280 modern buses.