Dirty diesel scrappage scheme unlikely to do much for air quality
A scrappage scheme aimed at removing the dirtiest diesel cars from the roads would have to be on a huge scale to have any significant effect.
Analysis by the RAC Foundation found that approximately 1.9 million diesel cars fall into the oldest, most polluting Euro standard categories: 1, 2 and 3.
They account for some 17% of all diesel cars on the road (11.2 million in total) and are responsible for 15% of total NOx emissions from diesel cars based on estimates of real world driving data and annual mileages from MOT records.
The analysis calculated what might happen if a scheme was implemented along the same lines as that run in 2009/10 as an economic stimulus for the car industry. This would take 400,000 of the oldest diesel cars off the road at a cost of some £800 million with the government and manufacturers both contributing £1,000 each to help people who trade in their existing vehicle replace it with a new model.
If every one of the 400,000 older cars was replaced with a new zero-emission electric vehicle then the cut in annual NOx emissions from the diesel fleet would be about 4,900 tonnes or 3.2% of the total emissions from diesel cars.
This drops to 2,000 tonnes per annum (1.3% of the total) if the scrapped cars were replaced with the latest Euro 6 diesel models and driven the same distance as those scrapped.