Environmental Engineering Reference
In-Depth Information
'footway' is itself reviewed. The full area of the highway (i.e. the public area between
frontage properties) is considered for 'roadspace reallocation' according to the relative
importance attached to the needs of its users, i.e. through traffic, buses, cyclists,
pedestrians, disabled motorists, parking and loading etc. Different combinations of
'shared space' are also considered. Comprehensive redesign is typically accompanied
by a review of street lighting and other elements of 'street furniture' - usually an unco-
ordinated and unsightly clutter of signs and installations of utility companies and
others which has accumulated over time and which often seriously impedes visibility
and pedestrian movement.
Design considerations recommended for both new and remodelled streets (though
predominantly the 'easier' residential variety) are set out in DfT (2007g). More
comprehensive, though unofficial, guidance on the design of mixed-use urban streets
is given in Jones et al. (2007).
14.8 Air quality management
As noted earlier, air quality was added to the list of purposes for which traffic regulation
orders can be made as a consequence of the 1995 Environment Act. The obligations
which derive from the Act are distinctive in two ways:
1
they are linked directly to a set of obligatory standards (unlike, say, noise where,
except in the case of new highway works, action by local highway authorities is
entirely discretionary)
2
these standards are derived from an EU directive (even though the impacts are
local in nature unlike, say, greenhouse gas emissions which are of international
significance).
Because of these obligations a set of procedures has been developed which is unique
in the field of traffic management. This is not because the instruments employed are
very different from those used to fulfil other objectives (although there are one or
two distinctive features) but because their application is undertaken in a much more
comprehensive and systematic manner.
Under Part IV of the Act. metropolitan and other unitary authorities as well as
district councils in two-tier areas in England are required to carry out regular reviews
and assessments of air quality in their areas. These are conducted in the context of the
prevailing national Air Quality Strategy (and in London according to the Air Quality
Strategy which the Mayor is required to prepare) and in terms of standards prescribed
in regulations made under the Act. (The standards set are for the seven pollutants
shown previously in Figure 3.8). The standards for the individual pollutants differ in
the time period over which concentrations are measured, e.g .as between hourly, daily
and annual means (Defra 2008a Table 1). In practice concentrations vary according to
local climatic conditions as well as variations in emissions from the relevant sources,
notably motorised traffic. For nitrogen oxide, particles (PM10) and sulphur dioxide
there are standards for more than one time period, with maximum levels set at higher
levels for the shorter time periods. In the most recent national strategy. standards have
been revised to focus on an 'exposure reduction' approach which is considered to be a
more cost-effective way of delivering improved public health (LTT 441).
Since 2003 authorities have been required to carry out their duties in accordance
with published guidance. Separate policy and technical guidance was published in
 
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