Letter published in Local Transport Today, Issue 808, 2 Oct 2020.

The great dirty diesel scare was sparked by the COMEAP report of 2010 which claimed particulates were causing “29,000 premature deaths” with an average loss of life of six months across the nation. The same report says that the 75% plausibility limits range from one sixth to double the cited numbers.

Well, if a “scientist” estimated the average height of a man as six feet but with  plausibility limits ranging from one foot to 12 feet, would we take any notice of him? So, why does anyone take notice of the COMEAP finding – especially when the statements depend, in part or whole, on the disgraceful process of elicitation, namely asking “experts” for their best guesses, presumably in the absence of data? Indeed Professor P. K. Hopke in an appendix to that report says, “I find the elicitation of experts to be an approach that involves too much subjectivity and is likely to be unreliable. I would suggest one be very careful using the guesses of experts as the basis of policy decisions.”

Worse still only about 50% of particulates come from exhausts with the rest from road, tyre and brake wear. These other items could be magnified by electric cars because of their greater weight.

Meanwhile we have Professor Michael Kelly and Gautam Kalghatgi pointing out the folly of the electric car in your columns.

Despite all that, the report has led to the virtual demise of the diesel industry.

Paul Withrington