Diesel cars: The dirty, deadly option?

When I could afford to own and drive a car back in 2007 living in Australia, I naturally chose a diesel-powered vehicle, thinking I would be doing my bit for the environment. Well hey, CO 2 emissions were lower than the gasoline-powered equivalent and the car was certified to the Euro 4 standard to boot, which meant to me something positive was being done about its emissions. (Note: I can't afford a car, neither do I need one in tiny Singapore where I'm based now. FYI, a Toyota Camry currently retails for around $113,250).

Even with my short history of diesel motoring long gone, my interest was aroused when I tuned into the BBC last night and watched Greg Archer, Clean Vehicles Manager at UK NGO Transport & Environment (T&E), highlight how dirty diesel vehicles were when actually driven on the road. Had we all been taken for a ride? I thought I'd better take a closer look. Much of the following information is quoted from a briefing by T&E entitled "Five facts about diesel the car industry would rather not tell you."

Apparently. testing conducted by the independent International Council on Clean Transportation (ICCT) has found that a typical modern Euro 6 diesel emits 7-10 times more nitrogen dioxides (NOx) on the road than the limit achieved in tests (80 mg/km ) in the laboratory . To pass lab tests, automakers reportedly employ 'cycle beating' to attain emissions levels typically five times lower than actual air pollution emissions on the road. One reason carmakers are able to manipulate testing is because they pay the organisations overseeing the tests and usually conduct these in their own laboratories. By the way, gasoline cars have a tighter NOx limit (60 mg/km) that is typically met on the road.

In tests by the ICCT, 12 out of 13 modern diesel cars failed to achieve the Euro 6 limit in on the road. The worst vehicle, an Audi, emitted 22 times the allowed limit. Emissions are highest in urban areas where most people are exposed to the pollution. On average a new diesel car emits over 800 mg/km of nitrogen oxides driving in town compared to the limit of 80 mg/km for Euro 6.

Data obtained on around 20 modern diesel cars by T&E shows every major manufacturer is selling cars that fail to meet Euro 6 limits on the road. A minority of vehicles do meet the limits - but most don't. This is because the industry uses cheaper, less-effective exhaust treatment systems or fails to configure the best systems in a way that minimizes emissions. The cost of a modern diesel after treatment system is just €300 .

T&E goes on to say that the current system for testing cars in a laboratory is obsolete and produces meaningless results - the figures quoted by industry website cleandieseltech.eu. T&E says the car industry is fighting to delay and weaken new "real driving emissions" on-road tests precisely because Euro 6 cars cannot achieve the limits set. The news comes as the Euro 6 auto emissions standard

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