The Air Quality Emissions and Health Benefits of Cleaner Buses: A City of York (UK) Case Study Using Micro-Scale Models and a Health Impact Toolkit

Background Air qualities on the heavily trafficked streets in the City of York are breaching the EU nitrogen dioxide annual average standard. City Buses are heavy-duty diesel vehicles that repeatedly ply their routes and make a significant contribution to the total volume of NOX emitted in York, particularly in central areas where building density, pedestrian activity and exposure to air pollution at their peak. The case for investing in cleaner Buses should be compelling if reliable vehicle emissions and air quality evidence was available, along with tools to economically evaluate health benefits. This UK case study attempts to make this environmental and economic case by bringing together calibrated and validated traffic and vehicle emission model results with the Cost-effectiveness of Air PolluTiOn Reduction model (CAPTOR) toolkit. Methods The movements of cars, vans, buses and commercial vehicles across the City York have been simulated at a detailed/ microscopic level as they negotiate traffic junctions, signals and interact with each other in weekday peak and off-peak periods. The traffic and instantaneous emission (PHEM) research models were configured to reflect the local, operational fleet i.e. mix of vehicle and fuel types in each Euro standard category. The resultant NOX emission factors are in agreement with published EU studies. The models were used to test the impact of replacing the fleet of 24 diesel Buses that service the York ‘Park & Ride’ sites with (a) new Euro VI diesel; and (b) full-Electric Vehicles (EVs) over the period 2017-2022. Results Replacing the ‘Park & Ride’ Buses with new, clean Euro VI diesels was simulated to lower the total road transport NOX emissions by 6.5% in the first year (2017). If this fleet were all EVs then the reduction was forecast to be 7%. Assuming a City of York population of 114,000, a £20,000 monetary value for QALY and lower-bound estimates of health endpoints the CAPTOR £4.65 million economic evaluation of health benefits in year one (2017) exceeded the £4.3 million cost of 24 Euro VI Buses. The EV fleet was estimated to save £5 million of health costs in the first year, only slightly less than the £7 million cost of purchasing the EVs and charging infrastructure. Conclusions The cumulative economic health benefit valuations (lower-bound) over the period 2017-2022 of the Euro VI and EV Park & Ride fleet were £25.7 million and £27.6 million respectively far exceed the capital investment in the Low Emission Vehicles