HC Deb 24 March 1993 vol 221 c608W
Mrs. Wise

To ask the Secretary of State for Transport what studies he has made of the different effectiveness of catalytic converters in reducing emissions as between long journeys and the short journeys more typical of urban travel; and with what result.

Mr. Kenneth Carlisle

The Transport Research Laboratory, the Warren Spring laboratory and the Motor Industry Research Association have all been studying emission rates from in-service vehicles equipped with catalysts, and their final report is expected by mid-1993. Preliminary data indicate that a catalyst has very little effect for the first kilometre. For longer journeys, however, average emissions of carbon monoxide, hydrocarbons, oxides of nitrogen, and carbon dioxide are reduced by:

  1. (a) for trips of 4 km, 62, 65, 58 and 15 per cent. respectively against journeys of 1km; and
  2. (b) for trips of 11 km, 76, 85, 62 and 37 per cent. respectively.

For trips beyond 11 km, further reductions are minimal.