We further investigated two certain events affecting invehicle
pollutant concentrations, i.e. idling of motorcyclists
at traffic lights and door opening at bus stops. On average,
each motorcycle trip had about 18 idling events and the
duration of each event ranged from 1 to 3 min. Bus doors were
opened 9 times each trip with 1 to 3 min each time. We
compared each idling event with an earlier driving event and
each door-opening event with an earlier closed door event of
the same duration, in order to determine whether the
exposure increased during those events.