Bus fleets are one of the largest contributors to poor air quality in cities, producing both nitrogen oxides (NOx) and particulate matter.
Looking to improve air quality, Ireland has committed to replacing existing diesel buses for the urban public fleet with low-emission alternatives, as part of their National Development Plan 2018 – 2027. Furthermore, since July 2019, Ireland has refrained from purchasing diesel-only buses for Public Service Obligation (PSO) services.
The trial tested four different technologies across fifteen buses, including electric, hybrid, compressed natural gas (CNG), and diesel. After simulating regular bus operating conditions, the testing showed that electric buses performed strongly across a range of metrics. Additionally, hybrid buses, when used in conjunction with hydrotreated vegetable oil, was also a viable alternative.
Emission Analytics was used to test tailpipe emissions and fuel consumption with Portable Emissions Measurement Systems (PEMS) on eleven of the buses (as the 3 electric buses had no tailpipe emissions).
In a report on the key findings of the low-emission bus trial, it was concluded that ‘the overall results suggest that electrification represents a feasible option for fleet transition, reducing carbon and air quality emissions while increasing renewable energy use in transport’.
