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A very frequently
applied measure in Italy and other countries is the so called “odd and even
plates”. This measure is far from ensuring a real reduction of 50% in daily
trips. In fact, families owning several cars can reschedule their use and
keeping the overall usage not far from the level without this kind of banning.
Moreover the enforcement of the restriction is not so easy and effective.
Anyhow, reductions of traffic volumes of a few 10% have been observed. Such
reductions have a relevance in absolute terms but do
not prevent an air pollution episode mostly caused by stable weather
conditions. The experience suggests that more drastic measures are needed.
Banning can be based on
a more ‘environmental’ criterion that the plate number: as an example we can
ban the more polluting vehicles.
In this case we talk
about “area restriction to polluting vehicles” or “low emission zones”. This
kind of solution has been identified as “the most effective tool for meeting AQ
standards” (EC Cantique project).
The emission reductions
in the restriction areas can be significant (10-20%) also if the total effect
on greenhouse gases emission at urban level can be modest. What is positive in
this kind of action is the good social acceptability linked to a cost effective
limitation of traffic and related emissions in the areas where a reduction is
particularly needed (see Topic Area restrictions to polluting vehicles (Environmental zones), Malmö - ENEA-DITS on “environmental zones” or details
and examples of application of this strategy).
Car free days represent
more or less complete banning events causing a drastic reduction of emissions
in the limitation areas but implying not huge reductions on the whole city
(10-20 % reductions are typical). The real goal of these initiatives seems to
be in the growing of the mobility users’ awareness about alternatives to
private trip by car, and we cannot, in fact, imagine now an extensive
implementation of such a measure over wide urban areas in weekdays.
The imposition of tolls and road
pricing when high pollution episodes occur is a less drastic and probably more
acceptable measure than complete banning, but so far, the evidence of reality
says that this kind of solution is applied mostly as a long-term measure
(bringing rather good results as in the recent London application). |