Volume II - Kildare.ie

N7 Naas Road Widening & Interchanges Scheme
Most of the serious conflict points, which exist on the DM network, will be removed
by the preferred scheme. This will resolve the problem of severe casualties arising at
the existing junctions along the N7, particularly at the uncontrolled at-grade
crossings. The number of personal injury accidents per year, on the mainline links,
will be reduced by at least 10% with the preferred scheme and even more scheme
accident benefits will be achieved at junctions, where an overall reduction of at least
70% per year can be expected.
A forecast of link and junction accident numbers was undertaken for opening year
2005 and design year 2020, with and without the N7 scheme. Link accidents were
calculated based on COBA10 rates per million vehicle kilometres and the SATURN
peak hour traffic flows, factored to the level of annual average daily traffic (AADT)
using 1999 ATC factors. The following COBA10 road type classifications were
adopted:
• Do minimum: older dual 2-lane all purpose carriageway (50mph), with accident
Environmental Impact Statement 109
June
2001
rate of 0.111 per million vehicle kilometres; and
• Preferred Scheme B2: modern dual 3-lane carriageway (50mph), with hard strips,
with accident rate of 0.100 per million vehicle kilometres.
Junction accident numbers were estimated for the key intersections across the
scheme network, based on COBA10 junction types and traffic inflow coefficients.
Peak hour traffic flows were taken from the SATURN model and converted to AADT
equivalents.
Predicted link and junction accidents for the DM and preferred scheme B2 are shown
in Table 9.1.3.3.
Volume 2