tarmac limited extension to borras quarry transportation
TRANSCRIPT
TARMAC LIMITED
EXTENSION TO BORRAS QUARRY
TRANSPORTATION ASSESSMENT
REF: RC4876/HJ/PS
Client Tarmac Limited
Client’s Agent Smiths Gore
Consulting Engineers Veryards Opus Ltd
Tunstead House
Buxton
Derbyshire
SK17 8TG
Tel: 01298 768 555
Fax: 01298 768 556
Croesnewydd Hall
Wrexham Technology Park
Wrexham
LL13 7YP
Tel: 01978 290 694
Fax: 01978 353 400
Burton House
Rossett
Wrexham
LL12 0HY
Tel: 01244 571 444
Fax: 01244 570 272
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
1
CONTENTS
Page
1.0 Introduction 5
2.0 Assessment Methodology 7
3.0 County Road Scheme / Existing Conditions 8
4.0 Proposed Development 11
5.0 Trip Generation 12
6.0 Trip Distribution 16
7.0 Assessment Years/Growth of Network Traffic 18
8.0 Existing Highway Access 19
9.0 Proposed Access Improvements 22
10.0 Accidents 26
11.0 Highway Impact 28
12.0 Conclusions 32
Tables
Figures
Appendices
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Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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List of Tables
Table 1 - Base Year (2005) Traffic Flows on A534
Table 2 - Hourly profile of vehicles leaving Quarry Sept 2002
Table 3 - Daily Trip Generation from Borras Quarry 2005
Table 4 - Predicted Daily Trips from Borras Quarry (2012-2024)
Table 5 - Predicted distribution of vehicles entering/leaving in AM peak hour – Yr 2017
Table 6 - Measured visibility at existing site access.
Table 7 - Summary of PICADY 4.1 Results – AM Peak Hour 2007
Table 8 - Summary of PICADY 4.1 Results – AM Peak Hour 2017
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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List of Figures
Figure 1 - Existing Quarry access
Figure 2 - Proposed Plant Crossing of Borras Road
Figure 3- Location of PI Accidents (2002-2005) – A534
Figure 4- Location of PI Accidents (2002-2005) – Borras Road
Figure 5 - Predicted Weekday Traffic Flows at 2017 – With & Without Development
Figure 6 - Modelled Flows – AM Peak PICADY Assessments 2007 / 2017
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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Appendices
Appendix A - ATC Data
Appendix B - Vehicle Speed Survey Results
Appendix C – Extract from Wrexham Industrial Estate Access Road Stage 2 Public Consultation
Appendix D - PICADY 4.1 Outputs
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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1.0 INTRODUCTION
1.1 This report has been prepared to assess the transport and access issues related to the
Planning Application submitted by Tarmac Ltd to extend Borras Quarry, Wrexham
onto land at Borras Airfield and the Holt Estate land.
1.2 This report updates and replaces the Transporation Assessment prepared by
Veryards in 2003, which was included within the Environmental Statement
submitted in support of the Planning Application. It takes account of recent
amendments that have been made to the Planning Application and uses
contemporary traffic flow and accident data for the road network around the site.
Background
1.3 Planning permission for the extraction of sand and gravel at Borras Airfield and
Caia Farm, the two existing operational areas at Borras Quarry, was granted in 1965
and 1990 respectively. An application for the determination of new planning
conditions, under the 1995 Environment Act, which included Borras Airfield, was
approved in 2001 and the Airfield site is now subject to modern planning
conditions.
1.4 In 1997 Bodfari (Quarries) Ltd submitted a planning application to extract sand and
gravel from the Holt Estate. Bodfari (Quarries) Ltd was subsequently acquired by
the Tilcon Group.
1.5 In 1999 Tarmac Heavy Building Materials UK Ltd submitted a planning application
to extend the depth of workings at Borras Airfield and Borras Hall Farm.
Subsequently, the Tilcon Group and Tarmac Group merged to become Tarmac Ltd,
a wholly owned subsidiary of the Anglo American Group.
1.6 Both the applications described in paragraphs 1.4 and 1.5 were undetermined by
Wrexham County Borough Council (WCBC), the Mineral Planning Authority, and
have subsequently been withdrawn.
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Transportation Assessment: August 2005
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1.7 This latest Planning Application proposes a revised working and restoration strategy
for Borras Quarry and the Holt Estate land, which has only become possible now
that all of this land is within Tarmac Ltd’s control.
1.8 The original planning application and accompanying Environmental Statement
(ES), was submitted in May 2003. It sought permission to continue working on the
existing Borras Quarry site, in a phased manner and to a selective depth below the
already permitted 62m AOD (but above the water table), and on the Holt Estate land
to the immediate north of the Airfield Site in 6 Phases.
1.9 This amendment now proposes the working of the Holt Estate land by eliminating
Phase 6 of the working programme and providing greater stand-offs from the limit
of sand and gravel extraction to residential properties. Phase 6 was intended to be
the last phase of working of the Holt Estate land but by excluding this phase it is
possible to retain a kettle hole and escarpment which were considered to be visually
important landscape features. Additionally, some minor boundary changes have
taken place on the southern area of the Holt Estate land. These revisions have been
brought about in response to issues raised by statutory and non- statutory consultees
and following the publication of the Minerals Technical Advice Note (TAN)
produced by the Welsh Assembly Government in 2004.
1.10 The blending ratio of the upper coarse sands and the fine lower sands remains the
same up to 2011 (2 upper coarse to 1 lower fine); from 2012 the blending ratio
changes to 1 to 1. The extractable sand and gravel resource has decreased from 14
million tonnes to 9.8 million tonnes within the Holt Estate land, giving an
extractable potential reserve of 17.7 million tonnes overall including the existing
Borras Quarry site.
1.11 The timescales for the proposal assumes that the Caia Farm sand and gravel
permitted reserve has been exhausted by the end of 2005. Working of the proposal
area would immediately follow the Caia Farm site and continue until circa 2030,
in a phased approach with progressive restoration following closely behind the
exhausted working phases.
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Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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1.12 The planning application for the Holt Estate land submitted by Bodfari (Quarries)
Ltd in 1997 included proposals for a new access onto the unclassified ‘Borras
Road’, which leads onto the A5156 Llan y Pwll Link Road. This latest application
does not propose such a new access because the ownership arrangement now in
place means that all materials can be delivered / exported from the quarry via the
existing access on to the A534.
1.13 A replacement of the existing plant crossing of Borras Road will, however, be
required to allow limited traffic movements between Borras Airfield and the Holt
Estate land and this is discussed later within this report.
2.0 ASSESSMENT METHODOLOGY
2.1 The assessment of traffic impacts is usually undertaken using guidance published by
the Institution of Highways and Transportation (IHT). In line with accepted
methodology, a meeting was held with Wrexham County Borough Council, the
Local Highway Authority (LHA) at which an outline of the key elements was
discussed and the scope of assessment required was agreed.
2.2 The LHA acknowledged that previous planning permissions allow unrestricted use
of the existing vehicular access; however, some concerns were raised about the
amount of visibility available to the right along the A534 west for vehicles exiting
the quarry. The Authority’s representatives therefore indicated that if, as a result of
the present application, network traffic increased by in excess of 5%, they would
wish to see an improvement to level of visibility afforded in that direction from the
existing access.
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Transportation Assessment: August 2005
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3.0 COUNTY ROAD SCHEME / EXISTING CONDITIONS
3.1 The LHA has a long standing proposal to improve access to Wrexham Industrial
Estate from the North and various alternatives have been the subject of Public
Consultation since 1987. The most recent proposal involved constructing a new
link road from the existing roundabout at A534/A5156 to the western side of the
Industrial Estate. This proposal would have reduced traffic flows along the A534 at
the existing junction to Borras Quarry.
3.2 The Minister for Environment at the National Assembly Government did not
confirm the Compulsory Purchase and Side Roads Orders for the scheme following
a Local Public Inquiry in February 2002. As a result, the LHA has recently
completed a ‘Stage 2 Public Consultation’ exercise at which four alternative routes
were presented for consideration.
3.3 The outcome of that process has recently decided in favour of the scheme that
involves a combination of upgrading and realignment of the A534 ‘Holt Road’
known as the ‘Blue Route’ (see plan at Appendix C). If the proposals are upheld by
the Executive Board and other statutory processes, then it is anticipated that work
on-site to construct the road could begin in 2008 subject to funding being made
available by the Welsh Assembly Government.
3.4 Consequently, traffic flows past the site access are not likely to be significantly
altered in the future, although, if the scheme is built, alterations to the existing
Quarry junction will be required as the outline scheme is for widening the A534 to
dual carriageway standard and an off-line realignment in the vicinity of the existing
Quarry access. These alterations would be the responsibility of the County Council
design team as part of the overall road scheme and any land-take requirements will
likely be met by Compulsory Purchase Orders.
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3.5 Due to the uncertainty in timescales and funding for the County scheme, it was
agreed that this report would evaluate the access arrangements on the basis of the
existing situation and that growth of base traffic, as presently recorded using the
A534, would be applied to future years on the basis that the County Council`s
scheme had not come forward.
Existing Site Access
3.6 The Quarry is served via a single access off the A534 Holt Road, Wrexham as
shown on Figure 1, (apart from the plant crossing on Borras Road). The principle of
this priority junction was approved in the 1965 planning permission for mineral
extraction at Borras Airfield. When consulted on the Application for Determination
of New Conditions under the Environment Act 1995, (granted in 2001) the Local
Highway Authority made no objection to the application on highways and
transportation grounds. These latest (2001) planning conditions for Borras Quarry
do not restrict the numbers of vehicles that can use the existing access and the time
limit for operations to cease at the Quarry extends to the year 2042.
Other traffic generators at the Borras Airfield site
3.7 Within the Borras Airfield site there are several other operations that generate traffic
and that use the same existing access with the A534 Holt Road. ‘Hanson’ operates
a concrete block production plant and an aggregate bagging plant and these generate
mainly heavy goods vehicle traffic. ‘Grampian Country Chickens’ generates a
modest amount of mainly light traffic; and the ‘St Christopher’s Eco Centre’
generates a very low level of light traffic. The traffic generated by all of these
operations is described in more detail in Section 5 of this report.
3.8 In terms of background traffic data, it was agreed at the meeting with the LHA that
the following would be obtained:-
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i) Automatic Traffic Count (ATC) data for the A534 (counter site west of
A534/Hugmore Lane Junction.
ii) Reported personal injury accidents along A534 between A534/A5156
roundabout and A534/Hugmore Lane Junction.
3.9 ATC data for the A534 from May 2005 (See Appendix A) and accident data for the
three-year period May 2002 – 2005 has been used as the base information for this
report.
3.10 With the agreement of the LHA, the National Road Traffic Forecasts (NRTF ’97)
‘low growth’ factors have been applied to these base flows when estimating future
traffic volumes.
3.11 Table 1 below shows typical 12-hour 4-day flows (Mon-Thurs) for the A534 in
2005. The table also shows peak hour morning and evening flows.
3.12 The morning peak period for traffic on the A534 is 08:00-09:00 hours for the
eastbound direction with the opposite (westbound) evening peak period being
between 16:00-17:00 hours.
A534 (Eastbound) A534 (Westbound)
Mon-Fri
average
12 hour
(Vehicles)
08:00 –
09:00
(Vehicles)
16:00 –
17:00
(Vehicles)
Mon-Fri
average
12 hour
(Vehicles)
08:00 –
09:00
(Vehicles)
16:00 –
17:00
(Vehicles)
May 2005 7379 1002 524 7656 522 1082
Peak Hour ratio of 12-hr
flow 13.5% 7.1% 6.8% 14.1%
Table 1 – Base Year (2005) Traffic Flows on A534
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4.0 PROPOSED DEVELOPMENT
4.1 The application site comprises Borras Airfield, where it is proposed to work below
the current permitted depth of 62 metres AOD, but above the water table, and the
Holt Estate land, where mineral will be extracted and transported by conveyor under
Borras Road to the existing processing plant at Borras Airfield, as presently occurs
where mineral is extracted from the Caia Farm site. It will be necessary, however,
for the conveyor location to be different from the present one.
4.2 Working and restoration will be phased progressively throughout the life of the
quarry as detailed in the Supplementary Statement and accompanying drawings.
Further information about the phasing of the workings is provided in the
Environmental Statement.
4.3 Restoration works will not involve the import or export of restoration materials
from the Site and all vehicle movements associated with these works will be
confined within the Site. Furthermore, there will be no inter-site movement of
restoration materials between the Borras Airfield and the Holt Estate areas.
4.4 The base data relating to output from Borras Quarry dates from 2002 when 611,275
tonnes of material was exported. It is at a similar level now and is expected to
remain at around that figure until the year 2012, after which it is anticipated to
increase to a peak of around 820,000 tonnes per annum. At these rates of
production the already permitted reserves, together with those within the
Application Site, are expected to last until around 2024 when output will fall to
approximately 402,000 tonnes per annum as a result of only the lower sands being
extracted.
4.5 The following Section will examine the traffic movements associated with the
existing operations at the quarry and the increase that is likely to be generated as a
consequence of the proposals comprising this planning submission.
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Transportation Assessment: August 2005
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5.0 TRIP GENERATION
5.1 Load ticketing information from Borras Quarry has been used to determine an
hourly profile of loads leaving the quarry and is shown below in Table 2. The
following data relates to September 2002, however, as noted above the output has
remained at a very similar rate since and therefore it is still representative.
Hours No. of Loads
for month
Volumes
(Tonnes)
Average No.
of Loads per
day
0600 to 0659 145 3030 6
0700 to 0759 337 6595 13
0800 to 0859 319 6147 13
0900 to 0959 248 4825 10
1000 to 1059 360 7184 14
1100 to 1159 310 6177 12
1200 to 1259 195 3849 9
1300 to 1359 264 5449 13
1400 to 1459 290 5868 14
1500 to 1559 273 5308 13
1600 to 1659 162 3237 8
1700 to 1759 1 16 1
TOTAL 2904 57685 126
Table 2 – Hourly Profile of Vehicles Leaving Quarry – Sept 2002
5.2 It can be seen that the vehicles leaving the quarry are generally distributed evenly
throughout the day between 08:00 and 17:00 hours. The figures in the table include
trips on Saturdays when the quarry is open for HGV movements between 06:30 –
12:00 hours and ticketing information shows that an average of 19 vehicles leave
the Quarry on Saturdays.
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5.3 Typically 126 heavy goods vehicles leave the Quarry each day. Weekday working
hours for HGV movements are 06:30 – 18:00 hours. On average 13 trips are made
to and from the Quarry on a weekday during the network morning peak, with less
than this generally occurring during the evening peak hour.
5.4 From the information provided, and as summarized in Table 2, each heavy goods
vehicle leaving the Quarry carries an average payload of around 20 tonnes.
5.5 The output from the Quarry in the year 2002 was 611,275 tonnes. On the basis that
there are 46 working weeks per annum, and 5½ working days per week, division of
the annual tonnage by the average payload figure typically equates to a predicted
122 loads per day. This compares well with the ticketing information provided by
Tarmac for September 2002, underlining the validity of the profile outlined within
Table 2.
5.6 Tarmac has advised that, in a typical week, 210 tonnes of aggregate is transferred
internally to the ‘Hanson Pre-Packed Products’ bagging operation. This material is
included in the annual output noted in Paragraph 5.5 above.
5.7 The operations at Borras Quarry also include the importation of limestone fines,
which are blended with sand and gravel from the Quarry and then exported by road.
The volume of limestone fines imported to Borras Quarry is currently around
65,000 tonnes per annum and, in line with the sand and gravel output, this is
expected to increase to around 90,000 tonnes per annum in 2012.
5.8 The majority of vehicles bringing limestone fines to the Quarry leave carrying sand
and gravel products, and hence an efficient “double haul” arrangement operates.
5.9 For the purposes of the assessment it is assumed that 10% of vehicles carrying
imported limestone fines leave empty. On a typical day, 13 vehicles enter the
Quarry carrying limestone fines and hence all but 2 leave carrying sand and gravel.
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5.10 Information concerning the heavy goods vehicle movements associated with the
concrete block plant operations out of Borras Quarry has been provided by Hanson
Concrete Block.
5.11 This information was included in a previous Transport Assessment, which was
prepared in support of a planning application to extend the depth of working at the
quarry in 1999. It is understood that there has not been any significant change to
output from the Block Factory since 1999; therefore this assessment assumes similar
outputs and traffic generation to the previous report.
5.12 In a typical week, 190 heavy goods vehicles deliver imported aggregates to the
Block Factory and leave empty and an additional 240 heavy goods vehicles arrive
empty and leave with finished products. For a 5 day working week this therefore
equates to 38 heavy goods vehicles trips for aggregates per day and 48 for finished
products.
5.13 An office block located within the southern part of the Airfield is leased by
Grampian Country Chickens. There are around 25 employees at the office and if it
is assumed that the Government’s transport energy unit figure of 70% typical car
usage for travel to work applies, this would result in 18 return staff trips per day for
that concern.
5.14 The ‘St Christopher’s Eco Centre’ is a small building within the southern part of the
Airfield and is used by local school and community groups. It attracts only a very
small number of light vehicles trips each day and employs 2 people.
5.15 The Quarry employs 16 staff directly, and applying the previously outlined ratio of
70% car usage for travel to work this would therefore give a predicted total of 11
return trips per day for these.
5.16 In summary, Table 3 below shows the total trips that are typically generated by the
current operations at the Borras Airfield site.
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Operations Vehicle Nos.
In Out
HGV’s Light
Vehicles
HGV’s Light
Vehicles Quarry - Sand and Gravel 115 126
- Limestone 13 2
Hanson Concrete Block (Aggregate) 38 38
Hanson Conc. Block (Finished Products) 48 48
Eco Centre 2 2
Grampian Country Chickens 18 18
Quarry Employees. 11 11
Total 214 31 214 31
Total (all Vehicles) 245 245
Table 3 – Daily Trip Generation from Borras Quarry 2005
5.17 The following paragraphs will review the increase in trips that are likely to result
from the Application proposals.
5.18 Based upon an output of 820,000 tonnes per annum over a 5½ day working week
for 46 weeks of the year, the number of heavy goods vehicles leaving the Quarry on
a typical weekday would increase to approximately 174, (assuming 25 trips are
made on a Saturday).
5.19 This represents an increase of 48 heavy goods vehicles per day from the present
time to the year 2012.
5.20 Similarly, there would be a concomitant increase in the importation of limestone for
blending with the sand & gravel from the present 65,000 tonnes per annum to
around 90,000 tonnes per annum and this would result in the numbers of heavy
goods vehicles associated with that task increasing from approximately 13 to 18 per
day. As previously explained, however, the majority of these vehicles subsequently
leave the Quarry carrying sand and gravel and hence all but 2 will already be
included within the 174 HGVs associated with outgoing trips from the Quarry, as
noted above.
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5.21 By comparing the present day HGV movements with those post 2012 (Tables 3/4) it
can be seen that the number entering and leaving the Quarry will likely increase
from approximately 214 to 262 per day. It is not anticipated that vehicle numbers
will increase beyond the 2012 rate and from circa 2024, output will progressively
fall until the Quarry workings are exhausted, circa 2030, and site restoration is
completed.
5.22 Table 4 shows the anticipated trips that will be generated at the peak output period
of operations at the Borras Airfield site between the years 2012 to 2024. The
figures assume that vehicle movements associated with the other operations at the
Quarry will remain as for the present day.
Vehicle Nos.
IN OUT
Operations
Heavy
Goods
Light
Goods/Cars
Heavy
Goods
Light
Goods/Cars
Quarry - Sand & Gravel
- Limestone
158
18
-
-
174
2
-
Hanson Concrete Block
- Aggregate
- Finished Products
38
48
-
-
38
48
-
-
Eco Centre - 2 - 2
Grampian Country Chickens - 18 - 18
Quarry Employees - 11 - 11
262 31 262 31
TOTAL 293 293
Table 4 – Predicted Daily Trips from Borras Quarry Years 2012 - 2024
6.0 TRIP DISTRIBUTION
6.1 Ticketing information provided by Tarmac indicates that the majority of heavy
goods vehicles leaving the Quarry turn right onto the A534 and travel west towards
Wrexham. A number of loads are delivered daily to Hanson’s Concrete Batching
Plant near to Borras Quarry - located just 500 metres west of the Quarry access
along the A534.
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6.2 The ticketing information showed that 91% of vehicles leaving the Quarry turned
right towards the A5156 (west) and that the majority of this traffic would then turn
right at the A5156/A534 roundabout to travel along the A5156 Llan y Pwll Link
Road for destinations north and south on the A483 trunk road. A small number of
vehicles turn left at the roundabout towards Wrexham.
6.3 Information provided by Hanson Concrete Block showed a similar pattern, with
89% of vehicles delivering aggregate turning left from A534 into the Quarry, and
around 70% of vehicles exporting finished product turning right towards the A5156
(west). Information from the Hanson Pre-Packed Products aggregate bagging
operation showed that 90% of traffic entered and left the Quarry from the A534
west (Wrexham side).
6.4 With regards to the Eco Centre and employees of Grampian Country Chickens and
the Quarry, based upon the above measured patterns, this assessment assumes that
90% of such traffic enters and leaves the Quarry from the west. The following Table
5 outlines the resulting flow distribution in the morning weekday peak hour at the
Quarry access to the ‘design year’ 2017. An explanation regarding the choice of
‘design year’ is provided below.
From
A534 West
To
A534 West
From
A534 East
To
A534 East
Quarry - Sand and Gravel 16 17 1 2
- Limestone 2 1 0 0
Hanson Concrete Block
(Aggregate)
5
5
1
1
(Finished Product) 6 4 1 3
Eco Centre 1 0 1 0
Grampian Country Chickens 17 0 2 0
Quarry Employees 11 0 1 0
Total 58 27 7 6
Table 5 – Predicted distribution of vehicles entering / leaving
Borras Quarry access during AM peak hour at Year 2017
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7.0 ASSESSMENT YEARS / GROWTH OF NETWORK TRAFFIC.
7.1 It is usual practice to deal with two or more assessment years for proposed
development impact and junction capacity analyses. The first is generally taken as
the year of opening and the second a period of 10 or 15 years after opening, this
being referred to as the ‘design year’.
7.2 In the case of existing or modified junctions a 10-year model is analysed.
7.3 This is undertaken in order to ensure that junctions have sufficient capacity to cater
for anticipated growth of network traffic as well as being able to accommodate that
generated by the proposed development.
7.4 For the purpose of this assessment the ‘opening year’ is assumed to be 2007 and
hence the design year will be 2017. It is usual practice to increase the volume of
existing network traffic to the future assessment years to reflect anticipated trends
and in order to provide a robust estimate of traffic flows likely to be using the roads
and junctions under consideration.
7.5 Base traffic flows (year 2005 See Table 1) to the years 2007 and 2017 have
therefore been increased by the application of ‘low growth’ factors as set out in the
National Road Traffic Forecasts published by the Department of the Environment,
Transport and the Regions (DETR), last updated in 1997 (NRTF97). The
assessments have been undertaken for the busiest hour on the network, this being
the 08:00-09:00 morning peak.
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8.0 EXISTING HIGHWAY ACCESS
8.1 The existing site access consists of a simple priority junction with merge and
diverge lanes on the A534 as shown at Figure 1. The junction does not include a
dedicated right turn lane for Quarry bound traffic from the east. At the point of
connection the A534 measures approximately 7.3 metres wide and includes a
1.5metre wide footway on the northern (Quarry) side. There is an area of widened
carriageway opposite the junction, which is sometimes used by heavy goods
vehicles when making a right turn from the Quarry. Access to a farm and houses is
also taken directly from this area.
8.2 The access road into the Quarry rises starts off at a shallow gradient before rising
sharply at an approximate gradient of 12% from a point around 10 metres back from
the edge of the A534 and continues to rise at a similar rate northwards along its
length into the main Quarry area.
8.3 From a visual inspection the Quarry access road appears to be in a good condition,
although some of the road markings near its junction with the A534 are worn.
Within the mouth of the junction parts of the carriageway adjacent to the A534 have
been recently repaired and this was carried out within the past twelve months as part
of the works to resurface the A534 - at which time fresh road markings were also
applied to the main road. (See also Section 9)
8.4 Measurements have been taken on site to determine the amount of available
visibility along the A534 for vehicles leaving the Quarry access. The A534 at this
point is derestricted (i.e. subject to the national speed limit of 60 mph).
8.5 Planning Guidance (Wales) Technical Advice Note 18 ‘Transport’ provides
guidance on desirable visibility distances at junctions. It states that, in the absence
of measured speed data, a junction joining a main road that is subject to a speed
limit of 60 mph should provide drivers with clear visibility for a minimum distance
of 215 metres along the major road (the ‘y’ distance) in both directions from a set
distance back into the side road (the ‘x’ distance).
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8.6 The ‘x’ distance varies from 2.4 to 9m depending upon the volume of traffic using
the side road and for an access such as at Borras Quarry the appropriate ‘x’ distance
would be 4.5m. The area contained within these measurements is generally referred
to as the visibility envelope.
8.7 Acceptance of a 4.5m ‘x’ distance in this case has been confirmed with the Local
Highway Authority and is considered appropriate for the junction, taking into
account the nature and volume of vehicles exiting the site and also reflecting the
fact that the seating position of drivers of heavy goods vehicles is generally closer to
the front of the vehicle when compared to car drivers. Visibility is required from an
‘eye height’ of 1.05m. This height is representative of most car drivers; however,
the higher seating position of heavy goods vehicle drivers’ means that they will
have an increased amount of visibility and therefore the distances measured should
represent a minimum value.
8.8 The following Table 6 shows the measured visibility distances at the existing
junction. Measurements were taken to the point where vehicles become visible
within the carriageway. Measurements are generally taken to the nearside, however,
the offside distance has also been measured in this instance to the east, as the A534
has double white centre lines at this point dictating that approaching traffic would
always be on the off-side.
‘x’ distance site
access.
Max ‘y’ distance
to the left
(looking east).
Max ‘y’ distance
to the right
(looking west)
4.5m 150m nearside kerb
160m offside lane 95m nearside kerb
Table 6 – Measured visibility at existing site access
8.9 In order to evaluate the visibility available against desirable minimum standards, a
vehicle speed survey was carried out at the existing Quarry access in accordance
with the Design Manual for Roads and Bridges (DMRB) Technical Advice Note TA
22/81. (See Appendix B for results of speed survey).
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Transportation Assessment: August 2005
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8.10 During the speed survey it was apparent that many vehicles travelled in ‘convoys’
behind heavy goods vehicles en-route to and from Wrexham Industrial Estate,
because of the lack of overtaking opportunities along the A534 between the A5156
roundabout and Hugmore Lane junction. Vehicle speeds were recorded in both the
morning and afternoon periods for a minimum sample of 100 vehicles in each
direction and these were measured under ‘free flow’ conditions. (i.e. vehicles
travelling in convoys as outlined above were ignored).
8.11 Technical Advice Note TA 22/81 requires that the 85th
percentile wet weather
speeds are then determined from the measured samples, and in this instance these
were calculated as being 53 mph for westbound traffic (towards Wrexham) and 51
mph for eastbound (towards Holt).
8.12 Where speeds have been measured in this way Design Bulletin DB32, published by
the Department of Environment and Transport (now DETR), specifies that the
visibility distance required along the major road can be amended to be
commensurate with existing site conditions.
8.13 In the case of the Borras Quarry access, this would therefore amend the ‘y’ distance
required to 160 metres in each direction.
8.14 In comparing the measured visibility outlined within Table 5 to that specified in
DB32 for new/improved junctions it is apparent that whilst adequate visibility is
available to the left, the visibility to the right is substandard and the Highway
Authority has expressed a desire that this be improved if possible. The works
proposed at the access as part of this latest planning application are outlined below.
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Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
22
9.0 PROPOSED ACCESS IMPROVEMENTS
9.1 The carriageway surfacing on the A534 past the junction has been replaced in the
past twelve months and consequently is in excellent condition and will offer a good
level of skidding resistance. As part of this work new road markings have also been
applied.
9.2 As noted within Section 8, a few of the existing road markings within the Quarry
approach to the junction with the main road are worn and would benefit from
replacement. The existing arrangement includes only edge of carriageway markings
along the A534, as opposed to ‘give way’ or ‘stop’ line markings as would typically
be expected.
9.3 There is presently no road lighting provided around the junction and the existing
access lacks ‘presence’ as there are no advanced signs to alert other road users on
the A534 to its existence, or that HGVs could be emerging ahead.
9.4 Whilst the access is generally in a good condition it is suggested that it would
benefit from a number of improvement measures including:-
• Application of high-friction surfacing within the Quarry access approach
• Replacement of the existing road markings with a ‘Stop’ line layout
• Inclusion of road lighting in the vicinity of the junction
• An improved signage strategy for each approach on the A534
9.5 These improvement measures would be developed in consultation with the Local
Highway Authority and could therefore be covered by an appropriate planning
condition, should planning permission be granted for the Quarry proposals.
9.6 Whilst the existing Quarry access does not have a poor accident history, as noted,
the LHA has expressed the desire that visibility to the right along the A534 for
vehicles leaving the Quarry be increased; to bring the amount afforded in that
direction in line with desirable minimum standards.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
23
9.7 Visibility from the 4.5m minor road distance is restricted by the presence of an
embankment and hence, in order to increase the amount available, it will be
necessary to set-back the embankment by means of a retaining wall. These works
involve land outside Tarmac Ltds ownership or control, however, Tarmac Ltd has
negotiated a possible means to deliver the improvement and have submitted a
separate planning application in respect of the required works.
9.8 It is noteworthy that Tarmac Ltd is aiming to carry out the visibility improvement at
significant expense, despite the fact that the existing access does not presently have
any restrictions on its level of usage. The Quarry access would be revised in the
future in any case as a consequence of the County Council`s ‘Industrial Estate
Access Road’ improvement scheme, however; the works outlined above are
intended to provide additional road safety measures in the interim period.
9.9 As noted earlier, the County Council has recently completed the “Stage 2 Public
Consultation” exercise in respect of the access routes serving Wrexham Industrial
Estate. This process has been required following the rejection of an earlier route at
Public Inquiry.
9.10 The latest Consultation process has found in favour of the ‘Blue Route’ scheme and
this involves upgrading the A534 between the A5156 Llan-y-pwll link and Borras
Hall Lane, a short distance to the east of the Quarry access.
9.11 From that point, a new road would be provided southwards into the Industrial
Estate. (See extract from Consultation leaflet provided at Appendix C).
9.12 The proposals involve widening the A534 to dual carriageway standard both on the
line of the existing road and in parts via new sections of road off the present line.
One of these off-line sections will be near to the Quarry access where the route is
shown to pass behind (to the north of) the Gredington Arms public house and
through the existing Quarry access road.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
24
9.13 Consequently, the County road scheme will sever the existing Quarry access road
and will, by necessity, require a replacement junction to be provided to serve the
Quarry. It is understood that as the A534 will be of dual carriageway standard the
replacement Quarry junction will comprise a left-in / left-out arrangement and hence
will require that all vehicles leaving the Quarry travel eastward to a proposed
roundabout at the end of Borras Hall Lane in order to turn west at that junction, if
that is their destination.
Replacement Plant Crossing of Borras Road
9.14 A very small number of Quarry vehicles currently cross Borras Road each day to
travel between the Caia Farm extraction site and the Borras Airfield site, which are
separated by Borras Road. The vehicles primarily comprise maintenance vehicles
and quarry related plant such as loading shovels.
9.15 Tarmac Ltd has recently carried out improvements to the existing crossing,
including the erection of new fencing to improve visibility and the provision of new
signing.
9.16 Once the Caia Farm site is exhausted, a new plant crossing of Borras Road will be
required as shown on Figure 2. This will operate on the same basis as the existing
crossing and is necessary to allow occasional quarry traffic to travel between the
proposed Holt Estate land and the Borras Airfield site.
9.17 The crossing would be used in the same way as at present which comprises a large
wheeled loading shovel which crosses the road at around 07:00 hours and 17:30
hours each day and a “pick-up truck” that may cross the road up to 8 times a day
between the hours of 09: 00 and 12:45 hours.
9.18 The location proposed for the replacement plant crossing has been discussed and
reviewed on-site with the Local Highway Authority.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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9.19 In order to minimize disruption to existing trees etc, the proposed crossing would be
located alongside the conveyor underpass that would pass beneath Borras Road.
9.20 Referring to Figure 2, the crossing would be located on a straight section of Borras
Road, however, there are two tight bends in the existing road to the south and these
serve to constrain vehicle speeds from that direction. Similarly, to the north of the
proposed crossing point the existing road is relatively narrow and has a sinuous
horizontal alignment.
9.21 Observation would suggest that the speed of traffic using Borras Road is modest and
it has therefore been agreed with the Local Highway Authority that visibility splays
of 4.5x90m would be provided to each side of the crossing. In addition, and in order
to give advanced warning to other road users, flashing signs would be installed at
each approach on Borras Road to indicate that the crossing was in use.
9.22 It is proposed that these warning signs would be activated by the quarry vehicles by
means of sensors located in the access tracks each side of the crossing and therefore
would only be called into use as and when required.
9.23 This would serve to reinforce the importance of the signs. Otherwise the infrequent
level of use of the crossing could result in drivers on Borras Road ignoring less
prominent signage systems, such as warning signs only containing text.
9.24 Provision of the required visibility splays at the plant crossing will necessitate the
loss of several existing trees and parts of hedgerows to each side of the road,
however, this loss would be compensated for elsewhere as part of the
comprehensive landscaping scheme proposed for the overall site.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
26
10.0 ACCIDENTS
10.1 Three years accident data has been obtained for the length of the A534 on the
approaches to the access to the Quarry from the A5156/A534 roundabout to
A534/Hugmore Lane junction and for Borras Road over the lengths covering both
the existing and proposed plant crossings. The locations and classifications of the
accidents are shown on Figures 3 and 4.
10.2 There have been two ‘slight’ injury accidents in the immediate vicinity of the A534
Quarry junction in the past three years with one of those involving a vehicle exiting
the Quarry access. One of the incidents comprised a rear-end collision between
three cars all travelling east along the A534, the reason for the accident being
unknown. The second occurred when a vehicle emerging from the Quarry collided
with a van on the A534; the driver of the vehicle leaving the Quarry claimed,
however, that the van driver flashed his headlights to signal for him to emerge.
10.3 There have been a further 21 accidents along the length of the A534 between the
A5156 and Hugmoor Lane during the last three years, however, none of these has
involved HGVs associated with the sand and gravel quarry at Borras Airfield.
10.4 The majority of the accidents have been as a result of car drivers losing control of
their vehicles and this may relate to travelling at speeds in excess of a safe limit
given the sinuous alignment of the existing A534. The data provided does not
indicate whether the road was wet or dry in these incidents, however, it is likely that
the recent resurfacing works carried out by the LHA will assist in this regard.
10.5 Two of the accidents were of the ‘serious’ injury category as in one the car over-
turned and rolled into an adjoining field and in the other a car strayed across into the
opposing lane, and hit an oncoming vehicle. All of the remaining accidents were
within the ‘slight’ category. There have been no fatalities on the road in the past
three years.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
27
10.6 The number of recorded accidents along the A534 is high and indicates that the
County Council`s proposed improvement scheme would undoubtedly result in
improved safety and a reduction in accidents in the future. The data provided does,
however, indicate that although the existing Quarry junction has substandard
visibility to the right (for traffic emerging from the Quarry) it does not have a poor
safety record.
10.7 In tandem with the improvements that are proposed at the access, as outlined in
Section 9, the accident data would suggest that the minor increases in traffic
movements associated with the Quarry proposals will not prejudice highway safety
beyond present levels. In fact, the measures outlined will result in improved
standards and potential safety gains for all road users in the vicinity of the Quarry
access.
10.8 With regard to Borras Road, there have been no reported personal injury accidents
at the existing plant crossing in the past three years. There have, however, been four
accidents further east nearer to the proposed plant crossing location.
10.9 Three of these have occurred at the tight bends that lie to the south of the proposed
crossing and in each case the cause has been loss of control. Two of these accidents
involved ‘slight’ injuries and 1 ‘serious’. All of the accidents took place in hours of
darkness and at a similar time of year with two occurring at the end of October and
one at the end of November. It is therefore feasible that slippery road conditions
may have been contributory factors in addition to the likelihood of excessive speed
for such conditions.
10.10 The fourth accident was of the ‘slight’ category and occurred to the north of the
proposed plant crossing when a car and tractor travelling in opposite directions
along the lane failed to stop in time and collided.
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Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
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10.11 Tarmac recognize that the proposed plant crossing will need to incorporate safety
measures such as conspicuous advanced warning signs and it is therefore proposed
that the final details be developed in close consultation with the Local Highway
Authority.
10.12 The proposed works could include a review of the existing road signs and markings
and enhancement of these local to the crossing, if deemed appropriate by the Local
Highway Authority.
11.0 HIGHWAY IMPACT
11.1 The ‘impact’ that the introduction of new traffic may have upon an existing road
network can be assessed in a number of different ways. The aspects most likely to
be affected can be examined and possible mitigation measures suggested, if
appropriate. Examples of potential impact areas include such elements as:-
• Negative influence on existing road users
• Sensitive locations (such as schools)
• Public transport
• Junction capacity
11.2 Relative to the above categories, the potential impacts could include such factors
as:-
• Community severance
• Safety, noise and intimidation
• Insufficient public transport provision
• Increased delays with associated safety reduction.
11.3 This report concentrates upon the possible physical traffic impacts relating to
highway capacity and safety issues.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
29
11.4 Figure 5 provides predicted weekday traffic flows on the approaches to the junction
for the ‘design year’ 2017, both with and without the development in order to
illustrate the resulting magnitude of change. The predictions in Figure 6
demonstrate that the increase in traffic up to 2017 resulting from the Borras Quarry
operations is insignificant in capacity or impact terms (i.e. less than 5%).
11.5 The ‘Guidelines for the Environmental Assessment of Road Traffic’ published by
the Institute of Environmental Assessment (IEA) (1992) provides accepted
thresholds at which ‘impacts’ from changes in the magnitude of traffic using a road
may be considered as being material.
11.6 ‘Rule 1’ of the guidelines states “include highway links where traffic flows will
increase by more than 30% (or the number of heavy goods vehicles will increase by
more than 30%)”.
11.7 ‘Rule 2’ states “include any other specifically sensitive areas where traffic flows
increase by 10% or more”. The ‘sensitive areas’ would apply where the
development traffic would all pass by a school, for example, or would use roads that
are already heavily congested.
11.8 The IEA guidelines provide data based upon previous research into discernable
environmental impacts and lists three categories; “substantial”, “moderate” and
“slight” for changes in traffic flows of 90%, 60% and 30% respectively. In relation
to changes in traffic volumes of less than 19% the guidelines state that noise impact
(for example) would be “not perceivable”.
11.9 This is because traffic flows on any road can fluctuate on a daily basis (typically by
approximately 10%) and so minor variations cannot be readily discerned. Highway
Authorities may request that capacity analysis be carried out at already congested
locations if the introduction of development generated traffic would increase the
volume using junctions by more than 5%. This does not apply to any of the existing
junctions used by quarry traffic beyond the site access itself.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
30
11.10 In line with the above therefore, the capacity of the Quarry junction has been
checked to the design year. Network traffic flows on the A534 were increased to the
year 2017 using ‘low growth’ National Road Traffic Forecasts as previously
described. The LHA has confirmed that low growth is appropriate for the A534 in
advance of their proposed improvement scheme, and this will provide a robust
assessment of the future years in a “do-nothing” situation in respect of that project.
11.11 The capacity of the Borras Quarry junction with the A534 has been assessed for the
opening and design year am peak hours using the flows shown on Figure 6.
11.12 PICADY 4.1 is a computer program for predicting capacities, queues and delays at
priority junctions. PICADY estimates capacity in terms of Ratios of Flow to
Capacity (RFC) and maximum queues (Q). The normally accepted maximum RFC
is 0.85 or 0.75 in the case of rural derestricted roads. However, RFC’s in excess of
these values may be acceptable if the associated queues and delays are within
reasonable limits.
11.13 The geometric parameters required for input to PICADY 4.1 for the Quarry junction
/ A534 capacity assessment were based on a combination of on-site measurements
and extrapolation of site survey data.
11.14 The design flows illustrated were input to PICADY 4.1 using the ‘Levels’ option to
synthesize a ‘normal’ peak period curve profile. The percentage of heavy goods
vehicles for traffic on the A534 was assumed to be 15% in each direction and a
same percentage value was applied to daily trips associated with Hanson Concrete
Blocks operations to estimate a robust peak hour figure.
11.15 The capacity of the Quarry access was assessed for the morning peak hour in both
2007 and 2017 and the results are summarized in Tables 7 and 8 below. The full
printouts are included in Appendix D.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
31
Road Demand/Capacity
(RFC)
Queue Vehicles
A534 (from Holt) 0.032 0
Quarry Access 0.273 0
Table 7 – PICADY 4.1 Results – AM Peak 2007
Road Demand/Capacity
(RFC)
Queue Vehicles
A534 (from Holt) 0.056 0
Quarry Access 1.25 3
Table 8 – PICADY 4.1 Results – AM Peak 2017
11.16 The results indicate that the junction is operating with plenty of surplus capacity at
2007 (i.e. traffic flows similar to the present-day) but that the addition of growth to
background flows to the design year 2017 has a negative influence upon the
capacity of the site limb (i.e. ‘gap’ availability is reduced). In the design year the
approach from the Quarry is shown to have no residual capacity and a queue of up
to 3 vehicles waiting to leave the site is predicted.
11.17 This situation would occur even without the very modest increase in traffic resulting
from the Quarry proposals, and it is noteworthy that it would not affect general
network traffic as no queuing of vehicles turning right from the A534 into the
Quarry is predicted.
11.18 It can be concluded that as the future hourly Quarry traffic flows are very similar to
present day, there will be no detrimental affects upon other more remote junctions
used by Quarry traffic, as the magnitude of change would not be discernable. (e.g. at
the A5156/A534 roundabout or A534/Hugmore Lane). As noted previously, traffic
generation associated with the proposed development will not result in a significant
(5% or more) increase in network traffic.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
32
12.0 CONCLUSIONS
12.1 The existing Borras Quarry junction onto the A534 has approval under previous
planning permissions and there are no restrictions on the numbers of heavy goods
vehicles that can use it. The Borras Airfield permission allows quarrying and
associated operations, including the use of the existing access, to continue up to
2042.
12.2 The proposed development will not significantly increase traffic movements at the
Quarry access above current levels and it has been shown that the existing junction
has sufficient capacity to cater for network traffic movements to beyond the design
year of 2017 (i.e. no delays are predicted on the A534).
12.3 The Local Highway Authority proposal to replace the A534 between the
A5156/A534 roundabout and Wrexham Industrial Estate will result in a significant
upgrading of the standard of that road and will necessitate replacing the access
currently serving the Quarry. This factor has been ignored within the assessments
carried out for this report.
12.4 It has been shown that the existing site access has a good safety record despite the
fact that visibility to the right at exit is less than desirable. Notwithstanding this,
(and the fact that consent for unlimited use exists), measures are proposed to
address identified deficiencies within the existing Quarry junction layout. These
improvements would be carried out to increase safety in the vicinity of the junction
for all road users in the interim period between the present day and construction of
the County Councils replacement road scheme for the A534.
12.5 A new plant crossing will be required on Borras Road to cater for a small number of
Quarry vehicle movements each day between the Holt Estate land and the Borras
Airfield site for future quarrying operations. The design of this crossing would be
developed in consultation with the Local Highway Authority and would incorporate
advanced warning signs for other road users.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
33
12.6 The improvements outlined at the existing Quarry access would similarly be
developed in consultation with the Local Highway Authority and would bring about
an increase in highway safety when compared to the present situation.
12.7 Overall, it has been shown that the application proposals would not increase traffic
volumes on the local road network by a degree that would be likely to result in any
discernable environmental or capacity impacts. In realistic terms the magnitude of
change will not be noticeable when compared to the present day.
Veryards Opus
Consultant Engineers
August 2005.
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
34
APPENDIX A
ATC DATA
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
35
APPENDIX B
VEHICLE SPEED SURVEY RESULTS
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
36
APPENDIX C
EXTRACT FROM WCBC INDUSTRIAL ESTATE
ACCESS ROAD STAGE 2 PUBLIC CONSULTATION
Tarmac Limited
Extension to Borras Quarry, Wrexham
Transportation Assessment: August 2005
37
APPENDIX D
PICADY 4.1 – OUTPUTS