Policy assessment using real-world emissions data from vehicles in Scottish cities

This technical note assesses various transportation policies put forth by major Scottish cities, Edinburgh and Glasgow, based on over 225,000 real-world emissions measurements collected in 2021.

The findings show that the first phase of the Scottish low-emission zones planned for 2023 in Glasgow and 2024 in Edinburgh would restrict diesel vehicles certified to Euro 5 or earlier and gasoline vehicles certified to Euro 3 or earlier which are responsible for around 50% of the total passenger car NO_x emissions while making up only around 20% of the total vehicle activity. The analysis further shows that including diesel Euro 6 vehicles not subject to Real Driving Emissions (RDE) testing in the LEZ restrictions would achieve additional emissions reduction as this vehicle group is responsible for 23 – 29% of total NO_x emissions from passenger cars.

The analysis also shows that the current policies targeting taxis and private hires do not address emissions from Euro 5 diesel taxis and private hires, a group responsible for over 35% of the total NO_x emissions from the fleet, in both cities. The findings highlight the importance of continuous monitoring of existing policies and preparation of future policy actions based on real-world data.