M20 - Cork to Limerick [preferred route chosen; in design - phase 3]

zulutango wrote: »

I don't recall seeing good reasons why it shouldn't go that way. Plenty of people obsessed with the N20 route though because that's what they know.

The Traffic section of the Pre-Feasibility report included the following :

o The study made use of existing traffic data only. Existing data compiled comprised
Automatic Traffic Count Data from NRA, Roadside Interview (RSI) Survey data, Manual
Classified Counts and NRA estimated counts along the N20 and N8.

o RSI data was used to construct trip matrices to summarise traffic demand on the N20,
N72, N8 and N24 routes. Data was coded to a system of 21 zones that allows the
capture of movements to and from key settlements within the study area.

o From this data the study built a likelihood matrix for each corridor option. If a trip is likely
to use the corridor a digit „1‟ is placed, and the same with a figure „0‟ in the case of not
using this corridor. The sum of results from this likelihood matrix is applied to the total
volumes for every pair to get the forecast of use of every corridor. In the case that both
options are equally likely for a particular trip, a figure „1‟ is placed in both matrices,
indicating that it could be captured by both options.

o Traffic volumes along the N20 are shown in the study. Traffic varies from near 25,000
vehicles AADT near Cork, around 17,000 between Cork and Mallow, near 20,000 in
Mallow at the N72 intersection, 10,000 to 11,000 between Mallow and Croom, and near
15,000 between Croom and Limerick. Around Limerick volumes are about 25,000. HCV
traffic remains relatively constant along the length of the corridor, with a percentage that
varies between 7 & 14%; the highest (14%) is between Cork and Mallow.

This study concludes that for long distance traffic either corridor option could be used based on
similar route distances. This is not the same for short and medium distance traffic movements. In
this case the Eastern Corridor would not attract significant volumes of traffic, as it does not pass
through any of the key locations of population, industry or employment, such as Mallow,
Charleville, Buttevant, Croom, Patrickswell and Blarney.

The study also showed that only a relatively small proportion of the existing traffic on the N20 is
travelling the full distance between Cork and Limerick or beyond. The analysis done on the N24
also suggested that almost none of this traffic travels beyond Tipperary.

To summarise the potential attraction for vehicles from the N20, the study provides a table
which indicates that only about 2,100 vehicles would be transferred to the Eastern
Corridor, and concludes that the majority of traffic using the existing N20 (Western
Corridor) will still use it or an improved version.

The additional information gathered as part of traffic study for the M20 scheme reinforces the
recommendations of the Pre-Feasibility Study in the following aspects:

- Strategic “Long distance” trips along the N20 route are between 20 to 30% of total flows.
Therefore remaining flows consisting of a minimum of around 8,000 vehicles and a maximum of
14,000 vehicles that would not be captured by a potential Eastern Corridor.

- Local and Commuter trips are very significant along the N20 route. In particular, traffic from
Mallow to Cork is very important, reaching volumes above 8,000 vehicles per day (adding flows
not only between these two main cities but traffic that is generated by intermediate zones inside
that section). This volume would not be captured by the Eastern Corridor.

- The Western Corridor option still provides for the strategic long distance trips and provides a
necessary upgrade to the existing N20 route to cater for significant traffic flows into the future.
We conclude that the recommendations of the Pre-Feasibility Report were correct and the Western
Corridor should be pursued as the route for the Atlantic Corridor.