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Slane Traffic Management Study Stage 1 Report
October 2012
Work in P
AECOM
Grand Canal House
Upper Grand Canal Street
Dublin 4
Tel (01) 2383100 Fax (01) 2383199
www.aecom.com
AECOM Slane Traffic Management Study
Page i
Slane Traffic Management Study
Stage 1 Report
Document No…….. 60275105
Made: ......................... Declan Keenan
Checked: .................. Shane Dunny
Approved: ................. Alan O’Brien
Document No. Revision Status Made Checked Approved Date
60275105 0 Final DK SD AOB 22nd
Oct 2012
AECOM Slane Traffic Management Study
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Executive Summary
AECOM has been requested by Meath County Council to undertake an analysis to assess the
impact of various levels of goods vehicle restriction through Slane Village. This report sets out
the results of the study. The analysis is based on collection of detailed origin and destination
data for goods vehicles through the locality, and is supported by a regional traffic model that
incorporates the M1, N2 and M3 corridors, in addition to all east-west connecting routes.
A total of seven possible scenarios for vehicle restrictions have been defined, which impose
restrictions on various roads in the vicinity of Slane Village, at levels ranging from 3 axle vehicles
up to 5+ axle vehicles.
In a review of similar projects, the study has concluded that a vehicle restriction in Slane would
likely operate in a manner that is similar to the Dublin City HGV Restriction. The scheme, which
was introduced primarily to address environmental and safety concerns, includes an online
permit system which ensures that necessary trips into the restricted area can be facilitated. The
review concluded that schemes for urban areas generally sought to shift large commercial
vehicle traffic to more suitable routes, or to encourage the use of smaller vehicles for access to
the restricted area.
The data analysis highlighted that approximately 20% of goods vehicle traffic across Slane
Bridge could be considered traffic that was using the N2 to avoid the M1. A further 25% was
legitimate N2 traffic travelling between Ardee/Monaghan and either Ashbourne or onwards to the
Greater Dublin Area. It is considered that a high proportion of this 25% could be encouraged to
transfer to the M1 under the right conditions. A further 49% of goods traffic is generated within
the broader Slane vicinity.
Following a detailed analysis of alternatives, it is concluded that the implementation of 5 axle
restrictions on Slane Bridge might represent the most manageable approach for implementing
vehicle size restrictions through Slane village. The proposal will generate slight safety benefits,
and an improvement in local air quality in Slane. It will reduce the volume of commercial vehicles
through Slane by approximately 42%, although the provision of a permit scheme for local access
will reduce this to below 40%. Nevertheless, this proposal brings with it a number of notable
adverse impacts:
It leads to an increase in goods vehicle traffic using the R152 and R153 as an alternative
to the N2 via Slane. The increase on the R152 is to the order of 300 vehicles per day,
with an increase on the R153 of approximately 100 vehicles per day;
It generates an increase in vehicle kilometres (and hence vehicle emissions), thereby
leading to a reduction in network efficiency as drivers seek longer routes to avoid the
restricted area; and
It reduces strategic accessibility between Ashbourne and the M1/Monaghan which is
currently available via the N2 corridor.
In light of the above impacts, it is questionable whether the traffic management proposals
presented in this report would yield a positive Business Case.
The previous N2 Slane Bypass scheme reflected an approach of delivering incremental
improvements along the N2, but within the ultimate frame of maintaining the N2 as a strategic
corridor. The proposal for vehicle size restrictions through Slane contradict the conventional
view of the N2 continuing to provide such a function, and would be more appropriately examined
in the context of a strategic plan for the M1, N2 and M3 corridors.
AECOM Slane Traffic Management Study
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Slane Traffic Management Study
Table of Contents
Page
1.0 Background .............................................................................................................................. 2
2.0 Existing Conditions .................................................................................................................. 4
3.0 Project Objectives .................................................................................................................... 5
4.0 Case Studies ............................................................................................................................. 6
5.0 Data Collection and Baseline Analysis ................................................................................ 10
5.1 Definition of a Study Area......................................................................................................... 10
5.2 Data Collection ......................................................................................................................... 11
5.3 Key Characteristics of Traffic Flows ......................................................................................... 12
5.3.1 Daily Flow Profile ...................................................................................................................... 12
5.3.2 Traffic Composition .................................................................................................................. 13
5.3.3 Vehicle Type ............................................................................................................................. 13
5.3.4 Average Weekday Daily Flow Calculation ............................................................................... 15
5.4 Analysis of Traffic Movements through Slane .......................................................................... 15
5.4.1 Total Matrix of Goods Vehicle Movements via Slane .............................................................. 17
5.4.2 Total Goods Vehicle Movements that could use N2 Slane Bridge .......................................... 18
5.4.3 Origin-Destination Patterns in Slane Village ............................................................................ 18
5.4.4 Extent of local trips using Slane Bridge .................................................................................... 19
5.4.5 Locally Generated 5-Axle Goods Vehicle Traffic ..................................................................... 19
6.0 Development of the Traffic Model ........................................................................................ 22
6.1 Conversion of AM and IP models to All Day ............................................................................ 23
7.0 Definition of Traffic Management Scenarios ....................................................................... 24
8.0 Scenario Testing .................................................................................................................... 29
8.1 Scenario 1: 5+ Axle Ban on Slane Bridge ................................................................................ 30
8.2 Scenario 2: 5+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon .................. 31
8.3 Scenario 2a: 4+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon ................ 32
8.4 Scenario 3: 3+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon .................. 33
8.5 Scenario 4: 3+ Axle Ban on Slane Bridge, on N2 between Slane and Collon, and on N51 .... 34
8.6 Scenario 5: Southbound 3+ Axle Ban on Slane Bridge, and N2 between Slane and Collon .. 35
8.7 Scenario 6: 3+ Axle Ban on Slane Bridge, but in southbound direction only ........................... 36
8.8 Summary of Traffic Analysis .................................................................................................... 37
8.9 Multi-Criteria Assessment of Alternatives ................................................................................ 37
9.0 Implementation of Preferred Scenario ................................................................................. 39
9.1 Overview................................................................................................................................... 39
9.2 Extent of Restrictions ............................................................................................................... 39
9.3 Management of Access/Permits .............................................................................................. 39
9.4 Mitigation of Impacts ................................................................................................................ 39
9.5 Conclusion ................................................................................................................................ 40
9.6 The Role of the N2 as a Strategic Route ................................................................................. 40
AECOM Slane Traffic Management Study
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1.0 Background
The basis for the N2 Slane Bypass arose out of the high volume of goods vehicle traffic which
was transiting the town via the N2 and the resulting road safety problems on the N2 through
Slane Village. The problems in the town centre were broadly acknowledged; noise and air
quality issues resulting from goods vehicle activity, and exacerbated by the steep gradient
leading out to the north and the south of the town. The safety issue was particularly notable, with
a number of incidents occurring in the town centre in recent years.
In 2001, a Traffic Management Scheme was implemented in Slane to address the significant
road safety issues that existed. The scheme complemented the existing shuttle system across
Slane Bridge and included the implementation of advanced traffic signals which provided priority
to light vehicles, and associated signage. This scheme did lead to a safety improvement, but at
significant journey time cost to non-goods vehicles.
The N2 Slane Bypass was intended to act as a long term solution to the existing issues in
addition to the existing traffic management measures. By removing a large volume of goods
vehicle traffic from the town centre, the scheme would provide significant safety and
environmental improvements to residents of the town, in addition to journey time savings for road
users. Following the preparation of the N2 Slane Bypass Scheme and its submission for planning
approval, the scheme was refused planning consent by An Bórd Pleanála in March 2012.
In its report, An Bórd suggested that the need for a bypass of the town had not been
demonstrated, and that lower cost ‘management’ measures which would achieve the desired
outcomes had not been fully explored. The findings are summarised below;
Due to the location of the bypass in the viewshed of Brú na Bóinne, An Bórd Pleanála
considered that the proposed bypass would be acceptable only where it has been
demonstrated that no appropriate alternative is available. Following on from the
submissions received and the oral evidence given during the Oral Hearing, An Bórd was
not satisfied that alternatives to a bypass have been adequately explored. In this context,
they considered that:
“The proposed development would have a detrimental impact on the setting
of the Brú na Boinne archaeological complex which would be contrary to the
heritage protection provisions of the County Development Plan” and that
“The bypass would be contrary to proper planning and sustainable
development, as it would tend to undermine the investments that had been
made improving the M1 and M3 corridors, and would have negative
implications for the quality of the environment and road safety along the N2
route.”
Whilst it was accepted that the Slane Bypass would assist in alleviating the high traffic
levels in the village in a north-south direction it will not impact upon the east-west traffic.
An Bórd also reported that the scheme was:
“likely to attract additional traffic, including a substantial proportion of
additional heavy commercial vehicles onto the N2 including a substantial
proportion of heavy commercial vehicles, onto the single carriageway N2
along its length, and through the settlements of Collon and Ardee”
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An Bórd also reported its conclusion that the proposed Slane Bypass would undermine
public investment given the current configuration of the overall national road network in
the region, and that alternatives to a bypass had not been fully explored.
An Bórd went on to state that although it has no role in developing regional transport policy or the
implementation of a traffic management system they suggested that traffic management in the
form of a HGV ban merited more investigation. The Board stated that potential negative impacts
for local business would need to be considered as would potential improvements on alternative
routes to alleviate safety concerns. An Bórd concluded that traffic management alternatives
might align well with the principles of proper planning and sustainable development, and ought to
be given further consideration.
As a consequence of the refusal of the scheme, AECOM has been requested by Meath County
Council to prepare a study that would assess the impact of various levels of goods vehicle
restriction through Slane Village.
This report sets out a quantitative analysis of the impact of goods vehicle size restrictions
through Slane. It sets out the process of data collection to understand existing traffic patterns,
aggregates goods vehicle traffic into appropriate size categories, and performs a network-wide
analysis of the reassignment impacts of a size restriction on the road network. The following
tasks have been undertaken:
Establishment of project objectives, to support comparison of alternative solutions;
Case Studies of vehicle restrictions in other locations, and their means of operation;
A detailed discussion of existing travel patterns through the undertaking of
comprehensive traffic and travel surveys;
Development of an analysis tool (traffic model) to support the assessment of impacts;
Identification of alternative Traffic Management Solutions;
Appraisal of alternatives, and selection of an emerging preferred solution that best fits the
project objectives; and
An exploration of key issues to be considered in the implementation of such schemes.
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2.0 Existing Conditions
The N2 National Primary Route is a strategic corridor connecting Dublin with Northern Ireland
and the border counties. The National Spatial Strategy identifies Monaghan as a ‘Hub’ which is
defined as:
“An important local node in transportation and communication terms: (a) on the
national road and rail or bus networks, (b) with access to a national or regional airport
(c) having adequate, reliable, cost effective and efficient access to port facilities (d)
with effective and competitive broadband access”
In this regard, the N2 is obviously seen as key to supporting the intended function of Monaghan
as a designated Hub.
Nevertheless, the M1 runs almost parallel to the N2 between Dublin and Ardee. Furthermore,
the M1 is connected to the N2 by a number of east-west routes of varying quality, most notably
the N51 (Slane – Drogheda), the R169 (Collon – Dunleer), the N33 (Ardee – Dunleer), and the
N52 (Ardee – Dundalk). This connectivity between both corridors leads to a notable degree of
traffic mixing between corridors on trips between the Greater Dublin Area and areas to the north.
The M1 currently charges a toll of between €1.80 for cars and €5.90 for 5-axle goods vehicles.
Understandably, this toll reduces the attraction of the M1 for trips, particularly for those who
might be otherwise drawn from the parallel N2 corridor.
Surveys undertaken in May 2012 showed that Slane Village currently caters for traffic flows of
over 13,000 vehicles per day. The surveys found that over 9% of the vehicles travelling through
the village are Heavy Goods Vehicles (HGV) and a further 11% are Light Goods Vehicles (LGV).
Slane Bridge itself experiences a traffic flow in the region of 7,000 vehicles per day of which 12%
are Heavy Goods Vehicles.
The existing N2 route passes through Slane village in a north-south direction as it descends from
high ground adjoining Slane Hill to cross the River Boyne Valley at a much lower level. The
route descends some 80m over a short distance of 1km, which leads to an average gradient of
8%, which exceeds the maximum permissible gradient of 6% for a single carriageway road. The
steep road gradient is a significant contributory factor to the traffic safety problems in Slane.
Further major safety problems arise at Slane Bridge over the River Boyne, where the road
alignment involves very sharp corners at the bottom of steep hills at both ends of the bridge.
This bridge is too narrow for two-way traffic, and a shuttle traffic signal system manages the flow
in alternate directions. Inherent traffic hazards arise from the seriously deficient road layout at the
bridge, and this has led to frequent accidents due to loss of control mainly by trucks. Following
the most recent fatal accident at this location in 2001, a major road safety scheme was
constructed in 2002, which involves separate signal control of light traffic and trucks with a
holding point in a safer location further up the hill where there is enough width for a virtual
escape lane for runaway trucks. In 2009 non-skid surfaces were reapplied on various road
sections around Slane however residual safety issues still remain due to the layout and
topography of the area as evident by the occurrence of a multi vehicle accident in 2009.
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3.0 Project Objectives
Project Objectives set out the intended outcome of any scheme, and are a driving influence in
the selection and definition of alternatives. Through appraisal of alternatives against project
objectives, solutions which best fulfil the particular needs of a project can be identified, refined
and shortlisted to produce a small number of possible solutions. Through more detailed analysis
(such as traffic modelling) the impacts of each alternative scheme can be quantified and a
preferred solution chosen.
The objectives of the N2 Slane Bypass project as set out in the Project Brief were defined as
follows:
(a) To improve traffic safety;
(b) To improve the environment of Slane Village by removing a significant portion of
north/south through traffic;
(c) To obtain an improved level of service suitable for a National Primary route;
(d) To achieve the objectives of various national and regional policies for the national
road network.
(e) To achieve an objective of the Meath County Development Plan 2007 – 2013.
It is considered that these objectives might not be fully relevant to the assessment of a Traffic
Management Solution, in that they dictate the identification of a new corridor. As such, the
objectives of the current exercise have been identified as follows such that they facilitate the
identification of a broader range of management solutions:
(a) To improve traffic safety;
(b) To improve air quality in Slane Village and other populated areas;
(c) To reduce transport emissions;
(d) To maximise the efficiency of the transport network; and
(e) To protect the accessibility of rural areas to designated Gateways, including the
Greater Dublin Area
In order to assess the comparative impacts of alternative schemes, a series of indicators will be
used as in Table 3-1 below.
Table 3-1: Project Objectives
Objective Measured By
Traffic Safety Aggregate PAG collision estimates based on road type
Air Quality Volume of goods vehicles through populated areas
Transport Emissions Total Vehicle kilometres travelled on the road network
Network Efficiency Total Vehicle hours travelled on the road network
Accessibility Impact on routing of restricted vehicles
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4.0 Case Studies
There are a number of HGV charging schemes in place in Ireland and throughout Europe. An
overview of a number of such schemes is presented below.
Dublin City HGV Cordon
The Dublin Port Tunnel opened on 20 December 2006 providing direct access between Dublin
Port and the national road network for Heavy Goods Vehicles (HGVs). Dublin City Council (DCC)
introduced the HGV Management Strategy to ensure maximum use of the Port Tunnel by port-
related traffic and to enhance the city centre environment. In order to implement the measures,
revisions were made to the Road Traffic (Control of Traffic) Regulations 2006 (SI 639 2006).
These revisions remain in place, and allow for other such schemes to be implemented under the
same regulations. The regulations (operative from 15 December 2006) provide for “the
application of regulatory provisions which include the regulation of traffic lane control in a road
tunnel, the imposition of prohibitions and restrictions on the entry to a specified public road by
certain non-passenger vehicles e.g. goods vehicles (by reference to total number of axles) with
provision to provide for operative periods and exemptions through issue of a permit...”
The DCC HGV Management Strategy was introduced on the 19th February 2007. The HGV
Strategy provides for a ban on 5-axle vehicles during the hours of 07.00-19.00 seven days a
week from a designated cordon area. A limited permit scheme has been incorporated which
allows 5-axle vehicles to load/unload within the city centre area. Large fines are in place for
entering the cordon area without a permit or for delivering to unregistered premises.
Figure 4.1 – Dublin City HGV Cordon Area
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The HGV Strategy has resulted in reductions of 5-axle vehicles within the city centre area of
between 80 - 94%. Dublin City Council issues an average of 200 permits per day for access to
the City Centre. Such permits are awarded for loading/unloading at a nominated site, or where
vehicles are not suitable for travelling through the Dublin Port Tunnel. Permits are obtained
through www.hgv.ie which was developed to allow for the expansion to other HGV permit
schemes throughout Ireland.
Enfield HGV Ban, Ireland
In 2006, Meath County Council implemented a HGV ban within the town of Enfield as outlined
below. The ban was enacted under the Local Government Act 1994 which gave Meath County
Council the powers to introduce a bye law, in this case referred to as the Enfield Traffic
Restriction Bye-Laws 2006. The ban restricts HGV’s with an unladen weight in excess of 3
Tonnes from travelling on certain links in the Enfield area to encourage use of the Enfield
Bypass. The banned links are highlighted in red below. The bye law exempts certain classes of
vehicles from the ban including emergency vehicles, public transport vehicles, vehicles based
within Enfield and vehicles with a specific delivery/collection in Enfield. Any person found on the
specified links not liable for an exemption will be subject to a €1,250 fine.
Figure 4.2 – Enfield HGV Ban Locations
London Lorry Control Scheme, United Kingdom
The scheme restricts the use of heavy goods vehicles to help minimise noise pollution in
residential areas during unsocial hours through restricted use of these roads. The Lorry Control
Scheme controls the movement of any heavy goods vehicles over 18 tonnes maximum gross
weight at night and weekends within the red boundary on the site map below.
During the restricted times, hauliers need special permits to be allowed to use their lorries on all
AECOM Slane Traffic Management Study
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but a very limited number of roads on a regulated basis. Permits can be obtained online or by
post/fax and are issued by the London Councils who manage the scheme.
Figure 4.3 – London Lorry Control Scheme Cordon Area
Liege City Centre HGV Ban, Belgium
A ban on HGV’s exceeding a defined length and weight was implemented in Liege, Belgium in
2006. Due to the city’s strategic location along a route between Germany and France, a
significant quantum of HGV traffic travelled through the city centre prior to the ban. This resulted
in significant noise pollution and congestion within the city centre. The ban was implemented in
order to ensure that HGV traffic utilised the nearby tunnel de Cointe provided for that purpose.
The HGV ban in Liege has proved successful with reductions in HGV volumes of approximately
45%. The scheme has resulted in benefits for the residents of Liege including reduced
congestion, noise and pollution within the city centre, in addition to a reduction in accidents.
Budapest Weight Limits, Hungary
A total truck weight restriction zone was implemented in 1996 in the city of Budapest. Freight
transport dedicated routes were also formed in order to control the delivery of goods within the
city centre. Various truck weight limits are applicable throughout a number of zones within the
city. Furthermore, the distribution of goods within the city centre is only possible with a permit
which has to be carried by each HGV.
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Goods Vehicle Restrictions, Monaco
All HGVs, regardless of their weight are banned from entering Monaco at various stages
throughout the day. The time restrictions are as follows: between 07.45 and 08.15, 11.30 and
12.30 and between 13.45 and 14.15. Furthermore, a permanent prohibition of vehicles
exceeding 8.5 tonnes is in place in Monaco, with these vehicles directed to an underground
facility within a shopping centre. It is noted that these measures help reduce air pollution and
noise within the city in addition to traffic congestion.
Conclusion
The case studies presented above represent a small number of a significant volume of similar
scenarios from across Europe. The evidence confirms that the application of restrictions on the
movement of large vehicles is a common mechanism for delivering environmental and safety
benefits in urban areas. The common feature of all schemes is that they seek to displace
commercial goods to more appropriate routes avoiding the restricted area, or to more appropriate
vehicles for accessing the restricted area.
Nevertheless, through the review of international experience it is clear that the majority of
locations do have some mechanism for facilitating access for specific circumstances, most
notably:
To facilitate deliveries or collections from nominated sites; and
Where vehicles are oversize and cannot travel on other routes (although this is perhaps
not relevant to Slane).
The experience in Dublin is particularly relevant, in that it has dealt with many of the legislation
and institutional issues which are required to implement commercial vehicle restrictions, and the
issuing of permits. Furthermore, the use of axles as a basis for restrictions has greatly simplified
enforcement, with visual inspection used to determine compliance or otherwise.
It should be noted that there are no examples of HGV ban’s on other National Primary Roads in
Ireland.
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5.0 Data Collection and Baseline Analysis
5.1 Definition of a Study Area
In undertaking the traffic analysis, it is necessary to define a Study Area within which the impacts
of any measures can be assessed. For the current project, it has already been noted that the
M1, N2 and M3 all play a significant role in providing for traffic flow through this area. In addition,
a large number of connecting corridors provide for traffic movements between these radial
routes.
The extent of the Study Area was defined based on the likely area of influence of any traffic
management measures in Slane as quantified by the National Transport Model (NTpM). The
resulting Study area is presented below in Figure 5-1. This area reflects the significant level of
competition between the M1 and N2 corridors and to a lesser extent between the N2 and M3
corridors. The study area extends as far north as Carrickmacross and Dundalk to account for any
long distance reassignment as a result of the proposed scheme.
Figure 5.1 –Study Area for Traffic Analysis
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5.2 Data Collection
A significant level of traffic data was collected in order to develop a full understanding of existing
traffic patterns and volumes through the Study Area. This data was collected in May 2012, and
included:
Goods Vehicle Origin-Destination (O-D) Surveys to understand vehicular routing through
Slane, the nature of goods being transported, vehicle types, and the extent of local traffic;
Automatic Traffic Counts (ATC) over 7 days, at sites across the Study Area; and
Journey time surveys were collected along key routes.
In specifying the Origin - Destination surveys, reference was made to the Inspectors Report from
the N2 Slane Bypass Oral Hearing, which outlined a need for more detailed traffic information.
The specification for the additional surveys was based on the following information requirements:
The definition of a series of screenlines and sectors which would allow the tracking of
goods vehicles through the region. This would allow longer distance traffic to be isolated,
and the origin and destination for more local traffic movements to be defined with
accuracy;
The collection of information on axle numbers for each goods vehicle, thereby allowing
the distinction between goods vehicles of different sizes. This would facilitate a more
detailed assessment of the impacts of HGV restrictions which would be targeted at
different vehicle sizes; and
The collection of data on vehicle type. Types include liquid tankers, retail palletised
transporters, construction vehicles, car transporters, buses and container vehicles. This
would support an understanding of the nature of goods movement through the area.
In specifying the surveys, it was important that the cordon for surveys was as closed as was
practicable – in other words, all routes that carry any reasonable volume of goods vehicle activity
were included in the survey to minimise leakage. The surveys were undertaken between 06:00 –
20:00 on an average weekday. The survey locations and the screenline/cordons are shown in
Figure 5.2.
In addition to the Origin Destination surveys, link counts using ATC’s were also undertaken at
each of the 22 sites over a 7 day period.
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Figure 5.2 – Survey Locations
Figure 5.2 – Survey Locations
5.3 Key Characteristics of Traffic Flows
5.3.1 Daily Flow Profile
In total, over 2,000 unique Goods Vehicles were found to access the survey area over the 14
hour period with each unique Goods Vehicle making approx 2.3 trips over the 14 hr survey
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period. The weekday flow profile of vehicles over Slane Bridge is shown in Figure 5.3, and
shows that the profile of Light Good Vehicles (2 axles) and Heavy Goods Vehicles (3 axles and
above) volumes over Slane Bridge are reasonably constant between 06:00 – 18:00 with volumes
dropping off outside those times.
Figure 5.3 – Traffic Flow Profile over Slane Bridge
5.3.2 Traffic Composition
Table 5.1 highlights the existing traffic composition on the approach routes to Slane village with
the LGV/HGV percentage significantly higher on the N2 than on the N51.
Table 5.1 – Slane Village Traffic Survey Findings
Location Cars LGV HGV
N2 North of Slane 75% 12% 13%
N2 South of Slane 76% 12% 12%
N51 West of Slane 86% 9% 5%
N51 East of Slane 88% 8% 4%
5.3.3 Vehicle Type
Examining the full study area, it was possible to develop a picture of the size and class of
vehicles using the road network in the vicinity of Slane. Table 5.2 outlines vehicle categories,
number of axles, and the contribution of each to total goods vehicle volumes.
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Table 5.2 – Origin Destination Survey - Vehicle Classification Results
Vehicle Category Axles
Total Daily Flows in Survey Area
Daily Flow through Slane Village
Daily Flow on
Slane Bridge
HGV1 – General LGV 2 26.2% 25.8% 23.7%
HGV2 – Retail LGV 3 1.9% 1.2% 1.8%
HGV3 – Construction/ Heavy Goods 3 1.0% 1.1% 0.7%
HGV4 – Other Vehicles 3 3.5% 1.9% 2.7%
HGV5 – Construction/ Heavy Goods 4 8.1% 9.0% 9.0%
HGV 6 – General Distribution/Retail Freight 5 47.2% 53.0% 52.1%
HGV 7 – Liquid Transporter (Non Fuel) 5 1.6% 0.5% 1.1%
HGV 8 – Liquid Transporter (Fuel) 5 0.4% 0.1% 0.2%
HGV 9 – Shipping Container 5 3.7% 1.1% 1.8%
HGV 10 – Automotive 5 0.1% 0.0% 0.0%
BUS1 – 2 Axle Bus 2 4.2% 4.1% 4.6%
BUS2 - 3 Axle Bus 3 0.1% 0.0% 0.0%
HGV11 – Other Vehicles 4 1.8% 2.2% 2.2%
The survey found that the most common type of Goods Vehicle in the survey area is the general
distribution 5-axle HGV (see HGV 6 in Figure 5.3 below) which accounts for 47% of Goods
Vehicles on a daily basis. Construction traffic accounted for over 9%, buses for a further 4% and
shipping container/liquid transport a further 5%. The remaining Goods Vehicles were smaller
general and retail Goods Vehicles. This highlights the dominance of large 5-axle Goods Vehicles
travelling through the Slane area.
Figure 5.4 – Goods Vehicles used in Survey Classification
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5.3.4 Average Weekday Daily Flow Calculation
The Goods Vehicle and Bus surveys were undertaken during daylight hours between 06:00 –
20:00. In order to factor 14 hr flows to average weekday daily flow a factor was ascertained from
the ATC counts undertaken at each survey point.
Table 5.3 –Conversion Factor
Location Site 24hr Flow 14 hr Flow
06:00 - 20:00
N33 East of Ardee 1 1355 1182
R171 North of Ardee 2 218 193
N2 North of Ardee 3 1981 1668
N52 West of Ardee 4 674 591
R165 West of the N2 5 149 134
R170 East of N2 and Ardee 6 87 79
R169 East of N2 7 529 470
N2 South of Collon 8 1403 1190
N2 North of Slane 9 1403 1195
N51 West of Slane 10 774 702
R163 East of R162 Kilberry 11 257 236
N51 North of Navan 12 723 652
N2 South of Slane 13 1311 1115
N51 East of Slane 14 445 411
N51 West of the M1 15 459 425
R168 South of Tullyallen 16 465 410
N2 North of R150 17 1541 1330
R150 East of N2 18 398 362
R153 West of Kentstown 19 663 595
N2 South of R153 20 1751 1505
N2 South of R152 21 2446 2118
R152 South of Duleek 22 771 704
TOTAL 19803 17267
14 hr to 24 hr Factor 1.15
Table 5.3 above outlines the calculation of the 14hr to 24hr factor used in converting the
following matrices to Average Weekday Daily flows.
5.4 Analysis of Traffic Movements through Slane
In order to present more detailed results, the Origin Destination matrices were compiled based
on a system of 15 zones (see Figure 5.4 below). Note that the zones at the periphery of the study
area are intended to represent external movements e.g. zone 1 includes traffic travelling onwards
via the N2 to Monaghan etc, whilst Zone 15 represents traffic travelling to/from Ashbourne and
Dublin via the N2.
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Figure 5.5 – Zones for HGV Traffic Patterns
Using the resulting matrix of goods vehicle movements, it was possible to undertake a number of
key analyses on the resulting dataset. These are presented below.
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5.4.1 Total Matrix of Goods Vehicle Movements via Slane
This analysis examines the total pattern of goods vehicle movement through the study area in
the form of a complete origin destination demand matrix.
Table 5.4 – Goods Vehicles - Daily Weekday Flows between Zones
Zone
To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 50 343 59 9 1 13 15 43 12 0 8 2 38 6 178 776
2 386 21 102 1 1 2 0 7 3 0 6 1 1 1 8 541
3 56 101 29 3 14 2 0 3 3 0 5 0 2 0 12 231
4 38 0 1 13 23 10 8 40 8 0 6 1 15 2 78 244
5 12 1 10 7 20 9 6 91 17 0 5 0 33 2 120 333
6 53 2 1 22 37 8 3 15 9 0 2 0 12 0 41 206
7 38 0 3 10 22 7 13 56 10 5 17 1 8 1 15 207
8 31 6 5 18 94 7 35 44 3 5 73 2 18 0 20 360
9 35 0 0 17 43 13 10 9 12 1 6 1 33 1 89 269
10 2 5 2 2 1 0 5 28 1 0 22 0 6 1 5 79
11 13 6 14 5 6 1 3 75 7 20 59 5 6 1 13 231
12 5 1 2 0 3 0 2 0 5 0 1 31 7 13 164 234
13 54 1 3 23 40 13 3 24 23 0 3 10 130 90 167 586
14 1 0 0 0 1 0 0 5 0 0 1 6 76 18 90 198
15 195 6 14 61 152 8 23 17 26 2 15 120 84 98 115 936
967 493 246 192 458 93 127 457 140 32 228 181 470 235 1113 5434
The analysis highlights a number of findings;
There is a large demand (729 vehicles) between Zones 1 and 2. This highlights relatively
high volumes of Goods Vehicles travelling between the M1 and N2 via the Ardee Link
Road;
There is a high Goods Vehicle demand (373 goods vehs) between Zone 1 and Zone 15.
This traffic is travelling between the N2 (North of Ardee) and the Dublin/Ashbourne
Areas. This is legitimate N2 traffic which could, under the right conditions, be encouraged
to route via the M1;
There is significant localised demand (1219 vehs) between zones 12, 13, 14 and 15
which does not impact upon Slane;
Finally, there is a flow of approximately 272 vehicles between Zone 15 (N2 near
Ashbourne) and Zone 5 (R169 adjacent to M1). Much of this traffic is using the longer N2
corridor as an alternative to the M1.
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5.4.2 Total Goods Vehicle Movements that could use N2 Slane Bridge
This second analysis examines those origin destination pairs that involve logical routing via
Slane Bridge. This gives a measure of total goods vehicle activity across the bridge on a daily
basis.
Table 5.5 – Goods Vehicles (incl buses) Daily Weekday Flows
Zone To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 12 2 38 6 178 236
2 3 1 1 1 8 15
3 3 0 2 0 12 17
4 8 1 15 2 78 105
5 17 0 33 2 120 173
6 9 0 12 0 41 62
7 10 1 8 1 15 36
8 3 2 18 0 20 44
9 35 0 0 17 43 13 10 9 1 6 134
10 1 0 6 1 5 13
11 7 5 6 1 13 31
12 5 1 2 0 3 0 2 0 0 1 15
13 54 1 3 23 40 13 3 24 0 3 166
14 1 0 0 0 1 0 0 5 0 1 8
15 195 6 14 61 152 8 23 17 2 15 493
289 8 20 101 239 33 39 55 75 3 26 13 139 15 489 1546
The analysis above suggests a total of 1,546 Goods Vehicles are likely to use Slane Bridge on
an average weekday. Further distilling of this data by vehicle size, it is possible to present this
potential demand as set out below.
Table 5.6 – Slane Bridge Demand by Vehicle Class
Vehicle Class Demand
Goods Vehicles (<= 2 axles) 406
Goods Vehicles (>= 3 axles) 1074
Buses 66
TOTAL 1546
Table 5.4 demonstrated a total of 272 Goods Vehicles using Slane as an alternative to avoid the
M1. The analysis suggests that such traffic represents only about 20% of the total commercial
traffic crossing Slane Bridge. When including the 373 vehicles that could be encouraged to
divert onto the M1, this suggests that 45% of goods vehicles crossing Slane Bridge are longer
distance movements that could be encouraged to transfer to the M1.
5.4.3 Origin-Destination Patterns in Slane Village
The patterns of Good Vehicles travelling through Slane on a daily basis were established using
the survey data. The results are presented in Table 5.7 below.
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Table 5.7 – Goods Vehicles (and buses) Daily Weekday Flows
Location N W S E
Northern Arm - 231 608 31
Western Arm 242 - 79 99
Southern Arm 691 94 - 30
Eastern Arm 56 111 44 -
As can be seen from above the main movements are north-south movements, representing
approximately 56% of all movements through the village. It is noted that approximately 20% of
goods vehicle traffic through Slane is associated with movement between the N2 North and the
N51 to/from Navan.
5.4.4 Extent of local trips using Slane Bridge
Table 5.8 – Daily Weekday Flows Goods Vehicle (and bus) to/from Internal Zones via Bridge
Zone To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 12 38 50
2 3 1 5
3 3 2 6
4 8 1 15 2 78 105
5 17 33 51
6 9 0 12 0 41 62
7 10 1 8 1 15 36
8 3 18 22
9 35 0 0 17 43 13 10 9 1 6 134
10 1 0 6 1 5 13
11 7 6 13
12 0 0 2 0 0 2
13 54 1 3 23 40 13 3 24 0 3 166
14 0 0 0 0 0
15 61 8 23 2 94
89 1 3 101 83 33 39 33 75 3 9 2 139 5 139 756
*Internal zones comprise zones 4, 6, 7, 9, 10 and 13
Local traffic is therefore 756 vehicles per weekday, and therefore represents approximately 49%
of the 1,546 goods vehicles travelling across Slane Bridge on a typical weekday.
5.4.5 Locally Generated 5-Axle Goods Vehicle Traffic
The survey data has been interrogated to isolate the quantum of 5-axle HGV traffic that is
associated with the Slane area. For the purposes of this assessment it has been assumed that
trips with a destination in Zones 6, 7, 9 and 10 are classed are trips requiring local access. In
reality a significant proportion of these will not require access to Slane Village as they will be
travelling from an area on the same side as their delivery location. An analysis of origin and
destination patterns for 5-axle vehicles is provided in Table 5.9.
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Table 5.9 –5 axle HGV traffic matrix (Weekday Daily Flows)
Zone To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 20 188 31 6 1 6 6 23 6 0 3 1 16 2 122
431
2 274 10 68 1 0 1 0 5 0 0 2 0 0 1 5
367
3 30 56 10 0 6 0 0 1 1 0 2 0 0 0 8
114
4 28 0 1 3 14 3 5 16 7 0 0 0 5 2 47
131
5 3 0 2 6 13 3 2 63 14 0 1 0 3 2 105
217
6 43 2 0 7 22 1 0 3 1 0 0 0 1 0 29 109
7 23 0 3 6 14 3 2 30 0 1 8 0 0 0 6 96
8 21 1 1 3 66 2 6 15 1 0 35 0 8 0 14
173
9 21 0 0 5 31 10 3 2 2 0 1 1 9 1 51 137
10 2 0 1 0 1 0 0 3 0 0 6 0 0 1 1 15
11 5 1 8 0 0 1 1 29 0 6 14 0 0 0 3
68
12 2 0 1 0 3 0 2 0 5 0 0 9 2 7 96
127
13 32 0 2 8 17 2 1 8 3 0 0 1 33 46 82
235
14 1 0 0 0 1 0 0 1 0 0 1 2 30 7 60
103
15 138 3 7 25 112 5 6 10 16 0 3 55 39 63 64
546
643 261 135 70 301 37 34 209 56 7 76 69 146 132 693
2869
There are in the region of 468 5-axle HGV’s with an origin or destination within the Slane area on
a daily basis. This accounts for approximately 12% of all 3, 4 and 5-axle goods vehicle activity.
Table 5.10 includes 4-axle HGVs in this assessment. This increases the daily local activity to
603 HGV’s per weekday, or 16% of all 3, 4 and 5-axle goods vehicle activity.
Table 5.10 – 4+ axle HGV traffic matrix (Weekday Daily Flows)
Zone To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 22 203 38 7 1 7 12 32 7 0 6 2 17 5 126
485
2 287 10 74 1 0 2 0 5 0 0 5 0 0 1 5
390
3 36 67 15 0 6 0 0 2 1 0 3 0 2 0 9
141
4 32 0 1 7 20 7 6 20 8 0 0 0 5 2 53
161
5 5 0 5 7 17 6 2 67 15 0 1 0 16 2 107
250
6 46 2 0 13 22 7 1 7 3 0 0 0 3 0 32 136
7 32 0 3 7 16 3 6 36 6 1 9 0 1 0 8 128
8 23 3 1 3 71 3 9 26 2 0 38 0 8 0 16
203
9 21 0 0 7 32 10 3 2 5 0 1 1 16 1 64 163
10 2 0 1 0 1 0 0 5 0 0 7 0 0 1 3 20
11 5 3 9 2 0 1 1 36 2 9 22 0 1 1 3
95
12 2 0 1 0 3 0 2 0 5 0 0 20 2 7 106
148
13 39 0 2 9 22 5 1 12 6 0 0 3 75 55 93
322
14 1 0 0 0 1 0 0 2 0 0 1 2 44 14 66
131
15 150 5 8 30 115 7 10 13 20 0 5 70 51 73 82
639
703 293 158 93 327 58 53 265 80 10 98 98 241 162 773
3412
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Finally, Table 5.11 outlines the origin destination activity for all heavy goods vehicles, showing
those vehicles that have origins and/or destinations within the Slane area. The inclusion of 3-axle
vehicles increases the total to 683, or 18% of all 3, 4 and 5-axle goods vehicle activity.
Table 5.11 – 3+ axle HGV traffic matrix (Weekday Daily Flows)
Zone To Zone
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fro
m Z
on
e
1 24 243 43 9 1 8 13 32 7 0 6 2 20 5 137
550
2 301 12 79 1 1 2 0 5 0 0 5 1 0 1 5
413
3 37 76 18 1 9 0 0 2 1 0 3 0 2 0 9
158
4 35 0 1 7 20 8 6 20 8 0 0 0 6 2 55
168
5 5 0 5 7 17 6 3 70 16 0 1 0 18 2 109
259
6 46 2 0 13 23 8 2 8 7 0 2 0 8 0 32
151
7 37 0 3 7 16 3 9 38 6 1 10 0 1 0 10
141
8 26 3 1 3 73 6 10 30 2 0 39 0 8 0 20
221
9 23 0 0 10 32 12 6 5 5 0 2 1 20 1 69
186
10 2 5 2 0 1 0 0 5 0 0 8 0 0 1 3
27
11 5 3 10 2 0 1 1 41 2 12 30 0 2 1 8
118
12 3 0 2 0 3 0 2 0 5 0 0 20 3 13 115
166
13 41 1 3 10 28 7 1 12 9 0 0 6 84 62 107
371
14 1 0 0 0 1 0 0 2 0 0 1 5 51 16 71
148
15 158 6 9 33 124 7 15 14 20 0 6 77 55 77 89
690
744 351 176 103 349 68 68 284 88 13 113 112 278 181 839
3767
.
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6.0 Development of the Traffic Model
A Traffic Model was constructed to support the assessment of traffic management alternatives
for Slane. The model was developed as a Local Area Model extracted from the National
Transport Model (NTpM), and has incorporated the extensive survey data collected for a base
year of 2012. The model development process followed the guidance set out in the NRA Project
Appraisal Guidelines, and was specifically developed to classify vehicles separately by axle
numbers in order to support testing of different vehicle restrictions. The traffic model also
included the M1 and M3 tolls such that the impacts of toll avoidance could be incorporated. The
Study Area for the Traffic Model is outlined below in Figure 6.1.
Figure 6.1 – Traffic Model Study Area
The development of the Traffic Models and the relevant inputs and assumptions is set out in full
in the Traffic Modelling Report which has been separately prepared for this project.
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6.1 Conversion of AM and IP models to All Day
A factor to allow the extrapolation of AM and IP period flows into Weekday Average volumes was
calculated using regression based on traffic data from 22 sites. A relationship was developed
based on regression analysis of local traffic data as set out in Table 6.1 below. The regression
analysis was based on weekday data and resulted in the following peak hour to Weekday
Average:
Table 6.2 – Regression Analysis Check
Location
Daily Flow
from
Surveys
Daily Flow using
regression % Difference
N33 East of Ardee 9717 9601 1%
R171 North of Ardee 2189 2111 4%
N2 North of Ardee 10096 9716 4%
N52 West of Ardee 5067 5531 -9%
R165 West of the N2 1394 1378 1%
R170 East of N2 and Ardee 953 918 4%
R169 East of N2 2962 3033 -2%
N2 South of Collon 6056 6104 -1%
N2 North of Slane 6413 6416 0%
N51 West of Slane 6595 6702 -2%
R163 East of R162 Kilberry 2174 2164 0%
N51 North of Navan 6107 6320 -3%
N2 South of Slane 6198 6205 0%
N51 East of Slane 4251 4426 -4%
N51 West of the M1 4623 4881 -6%
R168 South of Tullyallen 6172 6102 1%
N2 North of R150 7186 7325 -2%
R150 East of N2 3384 3458 -2%
R153 West of Kentstown 6371 6264 2%
N2 South of R153 10338 10320 0%
N2 South of R152 16418 16619 -1%
R152 South of Duleek 5937 6188 -4%
(5.33 * x) + (11 * y) = 5-Day AADT
Where,
x = AM Peak Period Flow
y = Inter Peak Period Flow
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7.0 Definition of Traffic Management Scenarios
A series of alternatives have been defined which seek to support the objectives set out in Section
3 of this report. During the identification of alternatives, it was considered that the existing
measures which have been implemented through Slane are targeted specifically at reducing the
safety risks associated with the passage of larger goods vehicles through the town. The
measures do not, however, lead to any environmental improvements, and in general lead to
increases in journey times for all vehicles.
The restriction of goods vehicles from the village brings obvious consequences for those who are
the subject of such restrictions. As such, the scenarios comprise a series of goods vehicle
restrictions which are applied across different locations, and apply to vehicles of different sizes.
In this way, the incremental impacts of the measures on goods vehicles, and on those living
adjacent to alternative routes can be understood.
Traffic Management Scenarios considered are outlined in Table 7.1 below. Note that the
terminology for vehicle restrictions is based on axle numbers, with 5+ referring to vehicles with 5
axles or greater.
Table 7.1 – Traffic Management Scenarios Tested
Scenario Description
1 Goods Vehicle 5+ Axle Ban on Slane Bridge.
2 Goods Vehicle 5+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
2a Goods Vehicle 4+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
3 Goods Vehicle 3+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
4 Goods Vehicle 3+ Axle Ban on Slane Bridge, on N2 between Slane and Collon, and
on N51 between M1 and R163
5 Goods Vehicle 3+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon,
but in southbound direction only.
6 Goods Vehicle 3+ Axle Ban on Slane Bridge, but in southbound direction only.
The traffic management scenarios considered are presented overleaf.
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8.0 Scenario Testing
The impact of the different scenario options has been assessed using the both AM and IP traffic
models for a traffic flow year of 2012 (Base Year). The models have been run by applying
restrictions on relevant links in the model for the specific user classes. The model then reassigns
traffic from within those restricted user classes onto alternative routes as appropriate. The
following information is then extracted from the traffic model results:
The pattern of traffic reassignment, showing alternative routes travelled and the extent of
traffic flow increase on those alternative routes;
Goods Vehicle traffic flows on key links across the Study Area Road Network, including
on the roads through Slane;
Total vehicle km travelled by all vehicles in the study area – this provides a proxy of fuel
consumption and resulting vehicular emissions; and
Total travel time travelled by all vehicles in the study area – providing a measure of
network efficiency.
The results of the traffic modelling are presented below (figures show AM peak impact) with
green bands representing an increase in traffic as a result of the scheme and red bands
representing a decrease.
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8.1 Scenario 1: 5+ Axle Ban on Slane Bridge
Scenario 1 will lead to a reduction of 66% in heavy
goods vehicle traffic (3 axles or greater) across
Slane Bridge, with a 52% reduction in 3+ axle
goods vehicles on the N2 immediately north of the
village.
An increase in HGV traffic on the M1 is evident, as
are decreases on the R169 and the N2.
Furthermore the HGV ban results in some HGV
trips utilising the R152 past Duleek to travel
between the M1 and N2 corridors.
The reduction in volumes on the R125 and R169
is likely associated with goods vehicle traffic
rerouting onto the M1 as the most direct route (i.e.
a reduction in M1 toll avoidance). The increase in
N33 traffic is likely as a result of N2 traffic
switching to the longer, but more appropriate, M1
corridor.
It is noted that Heavy Goods Vehicle flows through
the M1 Drogheda Toll increase by 21% over a full
weekday.
Table 8.1 – All (3 and above axles) HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 412 -65.7%
Chapel Street (N2) North of Slane 1142 553 -51.5%
N51 East of Slane 282 288 2.0%
N51 West of Slane 716 689 -3.8%
M1 Dunleer 3255 3773 15.9%
M1 Drogheda 863 1047 21.4%
R169 674 457 -32.3%
N2 North of Ashbourne Bypass 1899 1600 -15.7%
N33 East of Ardee 1002 1292 28.9%
R150 East of the N2 376 376 -0.1%
R152 East of the N2 674 991 47.0%
R153 West of the N2 480 589 22.7%
R125 between N2 and M1 255 196 -23.2%
R147 between Kells and Navan 891 902 1.2%
R168 South of Collon 146 184 26.1%
N52 395 427 8.3%
R162 442 459 3.7%
R163 175 142 -18.9%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
Option 1 has a significant positive impact upon Slane, albeit with some impact on local roads
which may require some mitigation measures. The majority of traffic is encouraged onto the M1
corridor, which provides a safer and less environmentally intrusive corridor for vehicles.
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8.2 Scenario 2: 5+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
This option again leads to an increase in goods
vehicle traffic using the M1, but introduces a
number of evident diversion routes, including the
N52, R162 and R168. The impact on the
N52/R162 is due to the restriction of the existing
movement between the N2 North and N51 Navan
Road through Slane, which as was shown earlier
accounts for approximately 20% of all heavy
goods vehicle movements through the town.
As such, the inclusion of a restriction to the north
of Slane Village leads to a more pronounced
reduction in goods vehicles than in Option 1, with
the reduction in heavy goods vehicles (3 axles or
greater) being to the order of 75% on Chapel
Street.
The impact on Slane Bridge, and on the M1
Drogheda Toll is relatively similar to Scenario 1.
Table 8.2 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 412 -65.7%
Chapel Street (N2) North of Slane 1142 288 -74.8%
N51 East of Slane 282 472 67.3%
N51 West of Slane 716 581 -18.9%
M1 Dunleer 3255 3952 21.4%
M1 Drogheda 863 1058 22.6%
R169 674 305 -54.8%
N2 North of Ashbourne Bypass 1899 1605 -15.5%
N33 East of Ardee 1002 1308 30.5%
R150 East of the N2 376 376 -0.1%
R152 East of the N2 674 996 47.8%
R153 West of the N2 480 589 22.7%
R125 between N2 and M1 255 196 -23.2%
R147 between Kells and Navan 891 902 1.2%
R168 South of Collon 146 200 37.1%
N52 395 459 16.4%
R162 442 551 24.6%
R163 175 142 -19.1%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
Option 2 therefore has a similar impact upon Slane Bridge as Option 1, but has a greater impact
upon the road network to the north of Slane particularly along N2 and R169. This option does
lead to higher level of rerouting via the N52 and R162 a result of the restriction on the north-west
movement through Slane Village.
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8.3 Scenario 2a: 4+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
Scenario 2a is an enhancement on Scenario 2, in
that the restrictions will additionally apply to 4 axle
vehicles.
The volume of 4-axle activity through Slane is
relatively low, at less than 60 vehicles per day.
This is significantly less than the number of 5-axle
movements across Slane Bridge on an average
day.
As such, the pattern of impacts of Scenario 2a is
similar to Scenario 2. The measures result in a
further reduction in traffic on the N2 at Chapel
Street and across Slane Bridge, with a moderate
reduction in traffic using the N51 west of Slane.
Table 8.3 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 310 -74.2%
Chapel Street (N2) North of Slane 1142 163 -85.7%
N51 East of Slane 282 451 59.9%
N51 West of Slane 716 527 -26.4%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
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8.4 Scenario 3: 3+ Axle Ban on Slane Bridge, and on N2 between Slane and Collon
The measures in Scenario 3 remove all goods vehicle
traffic of 3 axles or greater from the N2 to the north
and south of Slane. This suggests that residual traffic
will comprise solely of light vehicles, or goods
vehicles with only 2 axles.
The analysis presented earlier suggested that 2-axle
goods vehicles represent approximately 30% of all
commercial vehicles through the town. It would be
expected that much of this activity would be local,
relating to shop deliveries, refuse collections,
servicing of premises and agricultural vehicles.
The restrictions lead to traffic impacts that are similar
in pattern to Scenario 2 and 2a, with traffic increases
on the M1, and the various routes connecting the M1
and N2 (R152, N51, R168 and N33). The impact on
the N52, R162 and R153 via Navan is also evident.
Table 8.4 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 0 -100.0%
Chapel Street (N2) North of Slane 1142 0 -100.0%
N51 East of Slane 282 494 75.1%
N51 West of Slane 716 494 -31.0%
M1 Dunleer 3255 4251 30.6%
M1 Drogheda 863 1183 37.1%
R169 674 152 -77.5%
N2 North of Ashbourne Bypass 1899 1448 -23.7%
N33 East of Ardee 1002 1416 41.3%
R150 East of the N2 376 392 4.2%
R152 East of the N2 674 1093 62.2%
R153 West of the N2 480 660 37.3%
R125 between N2 and M1 255 147 -42.3%
R147 between Kells and Navan 891 902 1.2%
R168 South of Collon 146 313 114.9%
N52 395 497 25.9%
R162 442 643 45.4%
R163 175 125 -28.6%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
As with previous scenarios, scenario 3 has a significant positive impact upon Slane as traffic is
reassigned to a number of local roads which may require some mitigation measures. The 62%
increase in commercial vehicle traffic past Duleek on the R152 is noted, and will comprise a
mixture of vehicles of varying sizes.
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8.5 Scenario 4: 3+ Axle Ban on Slane Bridge, on N2 between Slane and Collon, and on N51
Scenario 4 restricts all heavy goods vehicles (3
axles or greater) from all roads approaching Slane
Village. The traffic modelling demonstrates that
such measures will have quite substantial impacts
on roads through the study area as a larger number
of vehicles seek alternative routes to avoid Slane.
The analysis shows significant decreases on the N2
North and South of Slane, the R169 and the N51
between Navan and Drogheda. Nevertheless, there
are significant increases on the alternative routes
around Slane, most notably the N33, N52 and
regional roads including the R162, R153, R152,
R150 and R168.
HGV traffic past Duleek would be expected to
increase by 40%, or about 200 vehicles per day,
with an increase of approximately 340 HGV’s per
day on the R153 through Kentstown. In essence,
the R152 and R153 would operate as informal
bypass routes of Slane to the south, with traffic
travelling via Drogheda/Navan and returning to the
N2 further north.
Table 8.5 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 0 -100.0%
Chapel Street (N2) North of Slane 1142 0 -100.0%
N51 East of Slane 282 0 -100.0%
N51 West of Slane 716 0 -100.0%
M1 Dunleer 3255 4017 23.4%
M1 Drogheda 863 1183 37.1%
R169 674 163 -75.9%
N2 North of Ashbourne Bypass 1899 1480 -22.1%
N33 East of Ardee 1002 1514 51.0%
R150 East of the N2 376 555 47.6%
R152 East of the N2 674 1115 65.3%
R153 West of the N2 480 817 70.2%
R125 between N2 and M1 255 147 -42.3%
R147 between Kells and Navan 891 929 4.3%
R168 South of Collon 146 362 148.8%
N52 395 807 104.5%
R162 442 898 103.2%
R163 175 70 -59.8%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
The results demonstrate the large reductions in goods vehicle movements through Slane, but
also the potentially substantial increases on other routes. Significant mitigation of impacts would
be necessary.
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8.6 Scenario 5: Southbound 3+ Axle Ban on Slane Bridge, and N2 between Slane and Collon
The safety concerns associated with southbound
traffic through Slane Village has been particularly
relevant in the development of the project
objectives. Scenario 5 seeks to remove the
southbound movement of all heavy goods vehicles
through Slane Village in order to address this
specific issue.
The results of the analysis show a range of
reassignment impacts for southbound traffic, with
the alternative routes being the N52/R162/R153,
R168/M1 and the N33/M1. The analysis also shows
an increase on the N51, which remains available as
an access route into Slane for local traffic.
Scenario 5 delivers a reasonable reduction in HGVs
over Slane Bridge with HGV flows decreasing by
approximately 50%. Total daily HGV traffic through
Slane Village decreases by 31% from 3,341 vehs to
2,313 vehs.
Table 8.6 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 603 -49.8%
Chapel Street (N2) North of Slane 1142 723 -36.6%
N51 East of Slane 282 412 46.0%
N51 West of Slane 716 575 -19.7%
M1 Dunleer 3255 3711 14.0%
M1 Drogheda 863 1030 19.3%
R169 674 414 -38.7%
N2 North of Ashbourne Bypass 1899 1666 -12.3%
N33 East of Ardee 1002 1160 15.8%
R150 East of the N2 376 398 5.7%
R152 East of the N2 674 832 23.4%
R153 West of the N2 480 600 25.0%
R125 between N2 and M1 255 191 -25.3%
R147 between Kells and Navan 891 902 1.2%
R168 South of Collon 146 254 74.1%
N52 395 449 13.7%
R162 442 524 18.5%
R163 175 109 -37.5%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
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8.7 Scenario 6: 3+ Axle Ban on Slane Bridge, but in southbound direction only
The analysis of a southbound 3+ axle restriction on
Slane Bridge shows a broad rerouting of goods vehicle
traffic from the N2 onto the N1 corridor, with reductions
on the R169 and R125 suggesting a decrease in the
levels of M1 toll avoidance. Although there are
increases on the R152, R153 and N51, these are less
significant than in previous options.
The results of the analysis show a range of
reassignment impacts for southbound traffic, with the
alternative routes being the N52/R162/R153 and the
N33/R168/M1.
Scenario 6 delivers a reasonable reduction in HGVs
over Slane Bridge with HGV flows decreasing by
approximately 50%. Total daily HGV traffic through
Slane Village decreases by 27% from 3,341 vehs to
2,434 vehs.
Table 8.7 – HGV Traffic across key links (Weekday - 2012)
Location Base Do Something % Difference
Slane Bridge 1201 603 -49.8%
Chapel Street (N2) North of Slane 1142 870 -23.8%
N51 East of Slane 282 293 3.9%
N51 West of Slane 716 668 -6.8%
M1 Dunleer 3255 3586 10.2%
M1 Drogheda 863 1030 19.3%
R169 674 500 -25.8%
N2 North of Ashbourne Bypass 1899 1655 -12.8%
N33 East of Ardee 1002 1155 15.2%
R150 East of the N2 376 398 5.7%
R152 East of the N2 674 821 21.8%
R153 West of the N2 480 606 26.1%
R125 between N2 and M1 255 191 -25.3%
R147 between Kells and Navan 891 907 1.8%
R168 South of Collon 146 205 41.0%
N52 395 411 4.1%
R162 442 464 5.0%
R163 175 120 -31.2%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
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8.8 Summary of Traffic Analysis
In order to support a comparative assessment of the alternatives, a summary of the findings are
presented below in Table 8.8.
Table 8.8 – Summary of Findings
Scenario
Parameter Base 1 2 2a 3 4 5 6
HGV Flow Slane Bridge 1201 412 412 310 0 0 603 603
Change % in HGV’s -66% -66% -74% -100% -100% -50% -50%
HGV Flow through Slane 3342 1942 1752 1451 988 0 2314 2434
Change % in HGV’s -42% -48% -56% -70% -100% -31% -27%
HGV Flow M1 Toll 863 1047 1058 ~1058 1183 1183 1030 1030
Change % in HGV’s +21% +23% +23% +37% +37% +19% +19%
HGV Flow on R169 674 457 305 ~305 152 163 414 500
Change % in HGV’s -32% -55% -55% -77% -76% -39% -26%
HGV Flow on N33 1002 1292 1308 ~1308 1416 1514 1160 1155
Change % in HGV’s +29% +31% +31% +41% +51% +16% +15%
* The provision of HGV permits to facilitate local access to Slane will reduce the above traffic flow impacts
8.9 Multi-Criteria Assessment of Alternatives
The analysis presented above demonstrates that the various scenarios can lead to substantial
reductions in goods vehicle traffic through Slane. Nevertheless, although this meets one element
of the project objectives, it is noted that the scenarios can lead to adverse impacts through other
populated areas, most notably Kentstown and Duleek. In addition, excessive restrictions can
lead to reductions in network efficiency as vehicles are required to route over longer distances to
access specific destinations. A broader assessment of the alternatives on the basis of project
objectives is therefore the relevant means for selecting the most appropriate solution. The
analysis methodology presented in Table 3.1 earlier in this report is therefore applied for the Multi
Criteria Assessment.
Safety The potential impact upon safety was accounted for by utilising accident rates for
each road type and vehicle kilometres on each road type extracted from the
various models. Benefits were calculated over a 10-year period.
Air Quality Reductions in goods vehicle movements through Slane are balanced against
increases through other populated areas – most notably Collon, Ardee, Duleek
and Kentstown.
Emissions Total kilometres travelled by all vehicles are extracted form the traffic models.
Efficiency Total hours travelled by all vehicles are extracted form the traffic models.
Accessibility The impact on accessibility between Dublin and Monaghan, and to/from Slane is
qualitatively assessed.
An Appraisal Summary Table is presented in Table 8.9 overleaf which summarises the key
impacts discussed above, and includes the network performance indicators as extracted from the
traffic models. Positive impacts are highlighted in green, with negative impacts in red.
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Table 8.9 – Appraisal Summary Table
Scenario Traffic Safety Air Quality Transport Emissions Network Efficiency Accessibility
1
Slight reduction in
accident costs due to
reassignment of larger
vehicles to M1. Benefits
exceed negative
impacts on local roads.
Slight reduction in HGV
traffic through
populated areas
Slight increase in
network vehicle km per
day resulting from the
reassignment.
Slight increase in
network HGV travel
hours per day resulting
from the reassignment
No significant impact on access to Slane for local
traffic as permit system will allow access. Access
to Monaghan available via the M1 and Ardee Link
(N33). Scheme will impact adversely on
accessibility between Ashbourne and the M1
Corridor/Monaghan. Overall Slight Impact
2
Slight increase in
accident costs, due to
increase in vehicle km
on non-motorway roads
Slight reduction in
HGV traffic through
populated areas
Slight increase in
network vehicle km per
day resulting from the
reassignment.
Slight increase in
network HGV travel
hours per day resulting
from the reassignment
No significant impact on access to Slane for local
traffic as permit system will allow access. Access
to Monaghan available via the M1 and Ardee Link
(N33). Scheme will impact adversely on
accessibility between Ashbourne and the M1
Corridor/Monaghan. Overall Slight Impact
2a
Slight increase in
accident costs, due to
increase in vehicle km
on non-motorway roads
Slight reduction in
HGV traffic through
populated areas
Slight increase in
network vehicle km per
day resulting from the
reassignment.
Slight increase in
network HGV travel
hours per day resulting
from the reassignment
No significant impact on access to Slane for local
traffic as permit system will allow access. Access
to Monaghan available via the M1 and Ardee Link
(N33). Scheme will impact adversely on
accessibility between Ashbourne and the M1
Corridor/Monaghan. Overall Slight Impact
3
Slight increase in
accident costs, due to
increase in vehicle km
on non
Moderate reduction in
HGV traffic through
populated areas
Strong increase in
network vehicle km per
day resulting from the
reassignment.
Moderate increase in
network HGV travel
hours per day resulting
from the reassignment
Moderate reduction in access to Slane for
service vehicles, and for general commercial
activity. Access remains available via N51. No
significant impact on access to Slane for local
traffic as permit system will allow access.
4
Moderate increase in
accident costs, due to
increase in vehicle km
on non
Strong reduction in
HGV traffic through
populated areas
Strong increase in
network vehicle km per
day resulting from the
reassignment.
Strong increase in
network HGV travel
hours per day resulting
from the reassignment
Strong reduction in access to Slane for service
vehicles, and for general commercial activity. No
significant impact on access to Slane for local
traffic as permit system will allow access.
5
Slight increase in
accident costs, due to
increase in vehicle km
on regional roads
Neutral net impact in
HGV traffic through
populated areas
Strong increase in
network vehicle km per
day resulting from the
reassignment.
Slight increase in
network HGV travel
hours per day resulting
from the reassignment
Slight reduction in access, with onward access
to Dublin Area and areas north remaining via N51.
No significant impact on access to Slane for local
traffic as permit system will allow access.
6
Slight increase in
accident costs, due to
increase in vehicle km
on regional roads
Moderate reduction in
HGV traffic through
populated areas (Slane,
Kentstown, Duleek,
Collon)
Moderate increase in
network vehicle km per
day resulting from the
reassignment.
Slight increase in
network HGV travel
hours per day resulting
from the reassignment
Slight reduction in access, with onward access
to Dublin Area remaining via N51. No significant
impact on access to Slane for local traffic as
permit system will allow access.
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9.0 Implementation of Preferred Scenario
9.1 Overview
The analysis presented in Table 8.9 demonstrates positive and negative impacts associated with
all options. Examining the outputs, it appears that Scenarios 1 and 2 can best support to the
objectives of the project.
Regardless of the final solution adopted, there are a number of further issues which are
necessary as part of any plan to restrict goods vehicles from Slane. In this regard, the key
impacts are those associated with:
The legislation within which any restrictions can be delivered;
the need to manage access through the issuing of permits, and subsequent enforcement;
the impact of traffic rerouting to alternative roads, and the impact on those areas;
These issues are discussed below.
9.2 Extent of Restrictions
The implementation of an axle restriction is facilitated by the current Road Traffic (Control of
Traffic) Regulations 2006 (SI 639 2006). The implementation of Bye-Laws is a reserved function
of the Local Authority, and would require the specific area within which the restriction applies to
be defined. In defining the specific area, attention would be required to appropriate advance
signage on key routes, the facility for turn-back at entry points, the provision of lay-bys where
drivers may make arrangements for permits at the point of entry, and the means of enforcement
(manual or automated).
9.3 Management of Access/Permits
The analysis has recognised that the restriction of goods vehicle movement through Slane can
have an adverse impact on accessibility for local businesses.
As with other successful schemes, the implementation of restrictions can be supported by a
system of permits which will allow managed access to the restricted area. As the level of
restriction increases, so too does the need for permits. Although more detailed analysis and
consultation would be necessary to understand the exact demand for a permit scheme, it is
anticipated that the daily demand for access would be substantially less than the 200 daily
permits issued by the system operating in Dublin City. Our analysis suggests that the daily
requirement for permits would likely be no greater than 50 permits per day. Ultimately, the
demand for permits will be related to the basis upon which permits are granted.
The permit system would be a natural extension of the system already established by Dublin City
Council, and the cost of permits would be set to cover the costs of administering that scheme. It
is anticipated that the cost of a daily permit would be in the region of €5 to €10.
9.4 Mitigation of Impacts
The risk of increased traffic volumes using the R152 and R153 has already been noted in the
analysis. It is likely that some road safety mitigation works might become necessary prior to
implementation of restrictions through Slane, such that the impact on these diversion routes can
be managed. This could comprise local junction treatment/speed limit or streetscape
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improvements, or potentially further restrictions on HGV activity. More detailed analysis is
necessary to understand the extent of mitigation measures that might arise out of the solution.
9.5 Conclusion
It is therefore concluded that the measures presented within Scenario 1 (5+ axle ban on Slane
Bridge) and perhaps Scenarios 2 and 3, might represent the most manageable approach for
implementing vehicle size restrictions through Slane village. Nevertheless, the proposals bring
with them a number of notable adverse impacts:
It leads to an increase in goods vehicle traffic using the R152 and R153 as an alternative
to the N2 via Slane;
It generates an increase in vehicle kilometres (and hence vehicle emissions), and a
reduction in network efficiency; and
It reduces strategic accessibility between Ashbourne and the M1/Monaghan which is
currently available via the N2 corridor.
From the analysis, it is considered that the imposition of a 3+ axle restriction would lead to
excessive impact on local services.
The phasing in of a any restrictions would be subject to the normal rules of project preparation,
as it will likely require supporting mitigation measures along some select regional roads.
Nevertheless, in light of the impacts of the proposed measures on network efficiency, it is
questionable whether the traffic management proposals alone would yield a positive Business
Case.
9.6 The Role of the N2 as a Strategic Route
It is noted that with any vehicle restrictions through Slane, the N2 will cease to function as a
strategic corridor for commercial traffic. This will impact most significantly on Ashbourne, where
transport-dependant industry will suffer a reduction in accessibility to the Dublin-Belfast
Economic Corridor via Drogheda, or the Monaghan Hub via Ardee.
The N2 Slane Bypass scheme reflected an approach of delivering incremental improvements
along the N2, but with the ultimate objective of maintaining the N2 as a strategic corridor. The
proposal for vehicle size restrictions through Slane contradicts the conventional view of the N2
continuing to provide such a function, and perhaps should be more appropriately examined in the
context of a strategic plan for the M1, N2 and M3 corridors.
Recommended