9 It can be observed that during the fi rst hour (H1) of the peak

9 It can be observed that during the fi rst hour (H1) of the peak period, journeys on foot resulted in a considerably lower level of CO exposure. 10 Although levels for journeys on foot generally exceeded those modelled for car journeys during H2, during the last hour (H3) the levels for journeys on foot were again frequently far lower than for car journeys.