Official Numbers of Diesel Vehicles in Cornwall
Here are the official figures received from Eloise at the Council:
*I have asked the Council to challenge these calculations and come up with a convincing alternative argument – they have yet to do so. I think it is because they can’t refute it!*
| Authority | Cars | Motorcycles | Light Goods Vehicles | Heavy Goods Vehicles | Buses & Coaches | Other Vehicles | Total | Diesel Cars | Diesel Vans |
| Cornwall UA | 296,300 | 17,400 | 54,200 | 4,200 | 1,300 | 15,800 | 389,200 | 131,900 | 51,700 |
| Diesel Cars | 131,900 | |
| Diesel Vans | 51,700 | |
| Light Goods Vehicles | 54,200 | |
| Heavy Goods Vehicles | 4,200 | |
| Buses & Coaches | 1,300 | |
| Total diesel vehicles | 243,300 | |
| Total licensed vehicles | 1,049 | |
| Licensed vehicles as a percentage | 0.43% |
Let’s go further and try and put this into real perspective
In order to get a real image of each type of vehicles impact, we need to convert other vehicles such as vans, buses and lorries into an equivalent against the average diesel car, to then show a true and understandable picture that will give us a real percentage share of the total for each of these vehicle types (please stay with me here).
For an average diesel car, an average of 12,000 miles per year is considered the norm. The current number of diesel cars being 131,900. So, based on the average:
If a licensed vehicle averages 48,000 mile per year, then that would equate to a multiple factor of 4 on the norm. Therefore, if there are 1,049 licensed diesel vehicles in Cornwall, that would equate to 4,196 diesel cars. Expected MPG for a diesel car would be between 40-50 mpg, so say 45 mpg.
An average van probably does the same average mileage of around 50k so again let’s say 48,000 miles, so giving a multiplying factor of 4, but the economy is not so good at around 30-38 mpg, so if we say 34 mpg, this would suggest a 25% reduction from a car, so giving a further multiplier of 1.33 to get the diesel car equivalent as a percentage. Therefore, if there are 51,700 diesel vans, then 51,700 * 4 * 1.33 gives a diesel car equivalent number of 275,044 diesel cars.
An average LGV probably has an expected average mileage of around 50k so again let’s say 48,000 miles, so giving a multiplying factor of 4, but the economy is not so good at around 18-25 mpg, so if we say 23 mpg, this would suggest a 50% reduction from a car, so giving a further multiplier of 2 to get the diesel car equivalent as a percentage. Therefore, if there are 54,200 diesel vans, then 54,200 * 4 * 2 gives a diesel car equivalent number of 433,600 diesel cars.
An average bus travels around 36,000 miles per year, so a multiple factor of 3 would apply. However, mpg is much lower for a bus, so another multiplying factor has to be considered here. The average bus mpg will depend on its size, so you would expect maybe 18 mpg from a smaller bus, where as a double decker will be around 9 mpg, so we will go down the middle at 15 mpg. So that would be a third of the mpg of a car, so giving a further multiple of 3. Therefore, if there are 1,300 buses, then 1,300 * 3 * 3 gives a diesel car equivalent number of 11,700 diesel cars.
An average HGV seems to come in around the same as buses, so travels around 36,000 miles per year, so a multiple factor of 3 would apply. However, being a little generous perhaps, the mpg is much the same as for a bus, so the same additional multiplying factor has to be considered here. The average HGV mpg will depend on its size, so you would expect maybe 18 mpg from a smaller HGV, where as a big arctic 40T will be around 9 mpg, so we will go down the middle at 15 mpg. So that would be a third of the mpg of a car, so giving a further multiple of 3. Therefore, if there are 4,200 HGVs, then 4,200 * 3 * 3 gives a diesel car equivalent number of 37,800 diesel cars.
So if the above calculations and assumptions are correct, then in ‘diesel car equivalent terms’ you would end up with these figures:
| Average Diesel Car Equivalent | Total vehicles based on average Diesel Car Equivalent | Share % | |
| Diesel Cars | 1.0 | 131,900 | 14.82% |
| Diesel Vans | 5.3 | 275,044 | 30.90% |
| Light Goods Vehicles | 8.0 | 433,600 | 48.71% |
| Heavy Goods Vehicles | 9.0 | 37,800 | 4.25% |
| Buses & Coaches | 9.0 | 11,700 | 1.32% |
| Total diesel vehicles | 890,044 | ||
| Total licensed vehicles | 4.0 | 4,196 | 0.47% |
So, Diesel Vans & Light Goods Vehicles amount to a whopping 79.61% of diesel pollution?
I have had comments from people who know the HGV business, and suggest the average annual mileage would be more between 50-70,000 miles per year. I don’t expect to have hit the bull’s eye with these numbers, but I am pretty confident I am inside the target area.
I hope you followed what I have done here, and I think this exercise really helps to put things into perspective if I have done this correctly, and if so, highlights where the real air quality issues are!
Addendum
If HGVs did between 50k &70k miles per year, then it would look like this: 60k equals a multiple of 5 on the average mileage, with a further multiple of 3 for economy, so 4,200 * 5 * 3 being the equivalent to 63,000 diesel cars.
| Average Diesel Car Equivalent | Total vehicles based on average Diesel Car Equivalent | Share % | |
| Diesel Cars | 1.0 | 131,900 | 14.41% |
| Diesel Vans | 5.3 | 275,044 | 30.05% |
| Light Goods Vehicles | 8.0 | 433,600 | 47.38% |
| Heavy Goods Vehicles | 15.0 | 63,000 | 6.88% |
| Buses & Coaches | 9.0 | 11,700 | 1.28% |
| Total diesel vehicles | 915,244 | ||
| Total licensed vehicles | 4.0 | 4,196 | 0.46% |