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Short-Term Engine Shut-Off: Pollutant Emission

Volume 590: debated on Thursday 11 June 1998

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asked Her Majesty's Government:What advice they give to car drivers in serious traffic jams about switching off their engines if they are likely to be stationary for a prolonged period. [HL2139]Further to the Written Answer by the Chairman of Committees on 1 June (

WA 12), whether they have carried out an environmental assessment of emissions from cars fitted with catalytic convertors to demonstrate the benefits of keeping engines running for different lengths of time as compared to switching them off; and, if so, whether they will place a copy of the assessment in the Library of the House. [HL2140]

Advice is regularly given to drivers in official publications recommending that a vehicle's engine should be switched off if the vehicle is likely to be stationary in traffic for more than two minutes.Research carried out in Germany shows that the benefits of switching off the engines of catalyst equipped cars for a given time can vary according to the pollutant under consideration—a matter of seconds with respect to oxides of nitrogen and fuel consumption but over five minutes with respect to hydrocarbons and carbon monoxide. In view of the fact that such times will vary further for different vehicle types and different levels of emission control technology, the Government have concluded that the general advice which they issue is appropriate for most vehicles in most situations. I have placed a copy of the report (in German with English abstract) entitled

Schadstoffemissionen und Kraftstoffverbrauch bei kurzzeitiger Motorabschaltung (Pollutant emission and fuel consumption with short-term engine shutoff) in the Library of the House.