An integrated program, incorporating all of these elements,
will generally be required to achieve an acceptable
outcome with respect to urban air quality. Focus
on only one or a few of these elements could conceivably
make the situation worse. For example, building
new roads, in the absence of measures to limit transport
demand and improve traffic flow, will simply result in
more roads full of traffic jams. Similarly, strengthening
public transport will be ineffective without transport
demand management to discourage car and motorcycle
use and traffic engineering to give priority to public
transport vehicles and non-motorized transport (bicycles
and walking).