From Dr Aat Peterse.

Sir, Another reason there are so few diesel cars in the US is strict air pollution standards ("Carmakers display a cleaner side of diesel", January 31). But as your article pointed out, the technology now exists to make cleaner diesel engines and several European carmakers have been showing it off at the Detroit motor show. It is strange then that the latest emissions standards for new cars proposed by the European Commission (Euro 5) do not take these technical advances into account.