Wayne,
there is a quite strong debate here now about diesel emissions and how many people that are killed each year by it. There are still cars being sold without filters for particulate matter, and there is only one diesel car that has technology to reduce NOx (Toyota Avensis D-Cat, only sold in the UK and Germany). I think that contributed to Toyota Prius becoming Car of the Year in Europe.
But the Toyota Prius is being challenged by new diesels with particulate filters. They still emit lots of NOx, but get fantastic mileage and emit hardly any particulate matter. See for example the 2005 Volvo S40 with a 48 mpg diesel:
http://www.volvocars.se/_Tier2/NewsE...ws/default.htm
Sorry, in swedish only. Couldn't find an english version.