TRUE publication
Real-world vehicle emissions in four major Scottish cities
The latest report from the TRUE Initiative concludes a three-year long remote emissions testing campaign in four Scottish cities under Transport Scotland’s Air Remote Sensing Project. From 2021 to 2023, approximately 1.4 million vehicle measurements were collected across Aberdeen, Dundee, Edinburgh, and Glasgow, providing a comprehensive picture of the Scottish fleet and allowing for greater insight into vehicle emissions over time.
With the completion of this testing campaign, conclusions can be drawn for the Scottish vehicle fleet over time. Key takeaways include:
- Measurements of NOx emissions from private passenger cars showed an annual rate of decrease of 7% with natural fleet turnover and without any additional policy intervention.
- Emission deterioration has led to the increase in fleet average emissions of taxis and private hires in Dundee and Edinburgh, despite the growth of cleaner vehicles in the fleet.
- Trends of NOx emissions over time varied by city for trucks, but the results from all four showed that Euro V trucks, some of the oldest in the fleet, are particularly prone to emission increases over time. They are also more likely to have defective or tampered emission control systems, highlighting the importance of identifying these trucks and removing them from the fleet.
This holistic picture of vehicles across Scotland also offers the unique ability to provide policy recommendations based on real-world driving conditions over time. At the national level, the Ministry of Transport could consider adding NOx emissions to the required annual vehicle testing program to identify and remove high polluters from the road. Locally, cities could consider enforcing milage or stricter age limits on taxis and private hire vehicles. Policy measures to accelerate fleet renewal and a transition to zero-emission vehicles could also be considered.
