[_h_o_d_]

It is reasonable to believe that these goals are both in mind! Edit: there's a new Diesel charge coming in soon, to reduce the extra pollution from these vehicles entering central london, for cars as well as lorries. In all the communications emanating from politicians and TFL it seems that numbers and pollution are both problems to be solved. Note also the new 'Boris' buses were designed as hybrids to improve air quality, even though in practice they don't work well and run on diesel mostly.