Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
Arup Consulting Engineers
3.10.5.1 Construction Phase
The difference in construction traffic associated with both options is negligible; therefore a
qualitative assessment of construction dust emissions only was undertaken for the purpose of
this report.
3.10.5.2 Operational Phase
As the proposed schemes will be grade separated, Breeze ROADS software was used to assess
the impact on air quality. Breeze ROADS is a dispersion modelling software package
specifically designed for grade-separated junctions. As such it takes account of elevations
associated with the junctions. Both opening years 2010 and 2011 were assessed.
The CAL3QHCR dispersion model, a feature of the Breeze ROADS package, was used for
the purpose of this assessment. This dispersion model processes up to a year of hourly
meteorological, vehicular emissions, and traffic volume and signalisation data in one model
run.
The Breeze ROADS model can be used with two types of link - free flowing and queuing.
Both types of links have been used for the purpose of this assessment. All of the junctions
which are signalised have been classified as queuing links, all other road sections have been
classified as free flowing links.
Breeze ROADS was used with CAL3QHCR to predict kerbside PM10 and NO2 concentrations
in the vicinity of the proposed interchange, where the impact of emissions from road vehicles
is expected to be greatest. The background concentrations of each pollutant were then added
to the calculated concentrations, to assess the cumulative impact (refer to Section 3.9.2.3).
Receptors were selected based on their sensitivity and their proximity to the proposed
interchange (refer to Figure 9.3 (Air Quality & Climate Chapter).
The National Atmospheric Emissions Inventory (NAEI) 11 provides a method for calculating
vehicle emission factors (g/vehicle per km) by applying year factors and speed factors to a
standard set of emission factors. This is calculated for a vehicle mix including both light good
vehicles (LGVs) and heavy good vehicles (HGVs). It was considered that the accuracy of this
method was suitable for the purposes of this study, because it is based on the same EU vehicle
emission standards as apply to Ireland. The calculated emission factors for the proposed
interchange are shown below in Table 3.10 below. AADTs for 2010 were used for the purpose
of this assessment as 2011 data was unavailable. This was considered acceptable as the
difference between 2010 and 2011 AADTs would be expected to be small and would not
affect the conclusions in terms of BREEZE ROADS modelling.
December 2007 Page 38