Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
Arup Consulting Engineers
3.12.2.3 Predicted impacts of proposed Interchange
3.12.2.3.1 Journey Characteristics
Do minimum option:
In the absence of the interchange, traffic volumes on existing roads in the vicinity will
continue to increase and congestion is likely to get worse. Given the importance of the Naas
Road (N7) as a regional link, together with the number of businesses in the area and the
volume of commuting traffic, this congestion will have a significant adverse impact on
journey time and journey time reliability.
Do-Something option:
In terms of Journey Characteristics, there is no particular distinction between the choice of
either an overpass or underpass option. In either case, the interchange will greatly facilitate
the flow of traffic in both the east-west and north-south directions.
The improved flow would be complemented by the road improvements already underway at
the Red Cow Interchange and on the M50. Without these road improvements, the existing
congestion at Newlands would simply be displaced elsewhere. The future connection
between the Blessington Road (N81) and the Galway Road (N4) that will be provided by the
Outer Ring Road will moderate the growth in traffic on orbital alternatives. Nevertheless, the
Fonthill /Belgard Road (R113) will continue to carry a substantial volume of traffic due to the
large amount of residential development in the area and the number of local businesses.
The two sets of traffic lights on the Fonthill Road will continue to induce some peak hour
congestion on this road. In addition, traffic lights will be needed at the interchange to permit
N7 traffic to join the Fonthill / Belgard Road (R113). Urgent journeys by emergency service,
specifically by the Fire Service located on the Belgard Road, will also be facilitated by the
interchange. For local vehicle journeys, the improved journey time and time reliability
represents a moderate positive impact for both alternatives.
A moderate positive impact is anticipated for pedestrian and cycle journey time and journey
time reliability too. Pedestrians heading to and from the bus stop will benefit most given the
number of signalised lights that they must currently negotiate. However, all pedestrians will
benefit from much reduced waiting times. Cyclists will benefit from reduced waiting times up
to a level experienced by vehicle traffic.
Construction:
During construction temporary diversions of Naas Road (N7) traffic will be accommodated to
the north and south of the existing lanes. Pedestrian pavements across the Naas Road could
run parallel to the lanes for the Fonthill / Belgard Road (R113), but could also be diverted
elsewhere possibly to a footbridge with possible implications for journey time. Of the two
alternatives, the underpass has the greater negative impact as it will require another year to
complete and could require further temporary bridging across the excavation to be put in place
for Fonthill / Belgard Road (R113) traffic. For both alternatives, it is likely that construction
will itself induce additional delays at some stage, although the time over which these delays
are significant should be much shorter than the full construction period. Furthermore, ongoing
improvements to the Red Cow interchange and to the M50 will be complete by this
time, reducing the cumulative impact on journey times for N7 traffic.
Overpass or underpass alternatives:
Selection of either an overpass or underpass is unlikely to make any significant difference to
journey times. The only significant difference occurs in the relative construction times, being
longer for the underpass alternative.
December 2007 Page 57