Robertson Barracks Traffic Study Trapp Architects and Department of Defence 23 January 2012 D R A F T
Defence Logistics Transformation Project (DLTP): JLU(N)
Robertson Barracks Traffic Study
AECOM Robertson Barracks Traffic Study Defence Logistics Transformation Project (DLTP): JLU(N)
D R A F T
Defence Logistics Transformation Project (DLTP): JLU(N) Robertson Barracks Traffic Study
Prepared for Trapp Architects and Department of Defence
Prepared by
AECOM Australia Pty Ltd Level 21, 420 George Street, Sydney NSW 2000, PO Box Q410, QVB Post Office NSW 1230, Australia T +61 2 8934 0000 F +61 2 8934 0001 www.aecom.com ABN 20 093 846 925
23 January 2012
60238192
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Quality Information
Document Defence Logistics Transformation Project (DLTP): JLU(N)
Ref 60238192
Date 23 January 2012
Prepared by Anukorn Chounlamountry
Reviewed by Isla Robertson
Revision History
Authorised Revision Revision Date Details Name/Position Signature
0 23 Jan 2012 Draft Report Matthew Jesson Associate Director
AECOM Robertson Barracks Traffic Study Defence Logistics Transformation Project (DLTP): JLU(N)
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Table of Contents 1.0 Introduction 1 1.1 Background 1 1.2 Purpose and scope of work 1 1.3 Report Structure 1 2.0 Existing conditions 2 2.1 Study area 2 2.2 Existing road network 3 2.3 Existing traffic volumes 3 2.3.1 Intersection counts 3 2.3.2 Intersection performance 7 2.3.3 Mid block traffic flow 8 2.4 Existing barracks operation 10 2.4.1 Barrack gate counts 10 2.4.2 Barrack generated traffic 11 3.0 Traffic Impact of Proposed Access Road 16 3.1 Proposal 16 3.2 Traffic redistribution 16 3.3 Intersection performance 18 3.4 New Barracks Access Intersection 18 3.5 Barrier Access Requirement 23 4.0 Summary and conclusion 24 4.1 Summary 24 4.2 Conclusion 24 Appendix A Council Traffic Data A Appendix B Robertson Barracks Access Gate Counts B
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1.0 Introduction
1.1 Background The Joint Logistics Unit (North) (JLU (N)) project purpose is to consolidate and provide material support to the Australian Defence Force (ADF) operations in Northern Australia - being all of the Northern Territory and northern Western Australia. The JLU (N) project is part of the wider Defence Logistics Transformation Project (DLTP). The support provided by JLU (N) covers warehousing and distribution, depot level repair and maintenance support services to regional and locally based dependent units. It also provides support to regionally based exercises and to overseas deployments. JLU (N) conducts operations at facilities at five sites in the Darwin area, being RAAF Base Darwin, three leased sites at Winnellie and an interim service station at Robertson Barracks. These sites are located relatively close to each other and are easily accessed. The DLTP proposes that JLU (N) will consolidate to a new Greenfield site at Robertson Barracks to reduce its facilities footprint at RAAF Base Darwin and vacate its three leased sites at Winnellie. This includes the relocation of: - JLU (N) Headquarters from RAAF Base Darwin to Robertson Barracks; - Explosive Ordnance section and contingency vehicle parking sites from RAAF Base Darwin to Robertson Barracks; and - Warehousing and vehicle maintenance sites from Winnellie to Robertson Barracks. JLU (N) will retain the existing special operations facilities at RAAF Base Darwin to provide cargo consolidation in support of operations, humanitarian and disaster relief programs. AECOM has been commissioned by Trapp Architects to prepare a traffic study in relation to vehicular access for Robertson Barracks, Northern Territory (the Barracks) as part of the JLU (N) project. Robertson Barracks is a major Australian Army base located in the outer Darwin, Northern Territory suburb of Holtze in the Municipality of Litchfield. Holtze is situated approximately 14 kilometres east of Darwin CBD, north of Pinelands, approximately four kilometres north east of Palmerston City. A new dedicated access road acting as an alternative access to service Robertson Barracks is proposed to be constructed from McMillans Road, entering the site to the south of the JLU (N) precinct.
1.2 Purpose and scope of work The purpose of the traffic study is to determine the performance of the existing road network surrounding Robertson Barracks and to investigate the impact to the local road network of providing an additional access road to Robertson Barracks.
1.3 Report Structure The report has been structured into the following sections: - Section 2 describes the existing land use and transport context surrounding the Barracks; - Section 3 describes the proposal, the additional access arrangements to the Barracks and the impact on the local road network; and - Section 4 provides a summary and conclusion for the report.
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2.0 Existing conditions
2.1 Study area Robertson Barracks is a major Australian Army base located in the outer Darwin, Northern Territory suburb of Holtze in the Municipality of Litchfield. Holtze is situated approximately 14 kilometres east of Darwin CBD, north of Pinelands, approximately four kilometres north east of Palmerston City. The Barracks is bound by Campbell Road to the north, Thorngate Road to the east, McMillans Road to the west and the Stuart Highway to the south. The Barracks was built in 1990 and is home to the 1st Brigade and 1st Aviation Regiment. The study area is shown in Figure 2.1.
Figure 2.1 Robertson Barracks study area
Source: Google 2012 AECOM Robertson Barracks Traffic Study 3 Defence Logistics Transformation Project (DLTP): JLU(N)
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2.2 Existing road network The major and local roads surrounding and providing access to Robertson Barracks include the Stuart Highway, McMillans Road, Farrar Road, Brandt Road, Stevens Road, Campbell Road and Thorngate Road. Brief descriptions of the roads are provided below. Stuart Highway is a four lane two-way carriageway running east west, located south of Robertson Barracks. It is a major highway connecting Darwin in the north to South Australia in the south. It has a posted speed limit of 100 km/hr in the vicinity of the Barracks. McMillans Road is a four lane two-way carriageway running west to south east, reducing to one lane in each direction in the vicinity of the Barracks. McMillans Road has a posted speed limit of 80km/hr. Brandt Road is a two lane two-way local road providing access to a residential area and is a link between McMillans Road and Campbell Road via Farrar Road. Brandt Road has a posted speed limit of 60km/hr. Farrar Road is also a two lane two-way local road providing residential access and connecting McMillans Road to Brandt Road. Stevens Road on the western side of the Barracks is a two lane two way road that connects Campbell Road in the north to McMillans Road in the south. Campbell Road is a two lane two-way road that intersects with the northern access to Robertson Barracks (Light Horse Drive). Campbell Road has a posted speed limit of 60km/hr. Thorngate Road is a two lane two-way road that intersects with the two eastern accesses to Robertson Barracks (Robertson Road and Courage Avenue). Thorngate Road has a posted speed limit of 80km/hr.
2.3 Existing traffic volumes 2.3.1 Intersection counts Intersection turning counts were collected at six key intersections on the local road network surrounding Robertson Barracks to determine the existing traffic conditions. AECOM commissioned Austraffic Pty Ltd to undertake the intersection turning counts over a three hour period in the morning and afternoon peak periods during a typical weekday. The times surveyed are as follows: - AM Peak - 06:00am to 09:00am; and - PM Peak - 15:30pm to18:30pm. The location of the surveyed intersections are listed below and shown in Figure 2.2. The surveys were conducted on the 8th December 2011. - Location 1: Intersection of McMillans Road / Farrar Road; - Location 2: Intersection of Farrar Road / Brandt Road; - Location 3: Intersection of Brandt Road / Stevens Road / Campbell Road; - Location 4: Intersection of Stevens Road / McMillans Road; - Location 5: Intersection of Stuart Highway / Tulagi Road; and - Location 6: Intersection of Stuart Highway / McMillans Road.
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Figure 2.2 Intersection turning counts outside Robertson Barracks
Source: Google, 2012 An excel spreadsheet has been developed showing the AM and PM peak hour network flows of the surveyed intersections as shown in Figure 2.3 and Figure 2.4. The peak hour is the hour within the surveyed time period where the most amount of traffic occurs. Turning counts for intersections 1, 4, 5, and 6 are based on the network peak hour; 07:00-08:00 and 16:30-17:30 for AM and PM peak hours respectively. Peak hour turning counts for intersections 2 and 3 are independent of the network peak hour. The purpose of this is to assess the worst case scenario for intersections 2 and 3 where traffic flows are higher due to traffic generated by the Barracks. The peak hours used for intersections 2 and 3 are 06:30-07:30 and 15:30-16:30 for AM and PM peak hours respectively. It should be noted that the time period the traffic surveys were undertaken on the local road network coincided with the Barracks Reduced Activity Period and therefore it is assumed that less traffic generated by the Barracks would have been present on the external road network compared to a typical day. To account for this the weighting of Barracks generated traffic as part of the overall traffic has been increased by 20%.
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Figure 2.3 AM peak hour network flow
Source: AECOM, 2012
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Figure 2.4 PM peak hour network flow
Source: AECOM, 2012
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2.3.2 Intersection performance An assessment has been undertaken to determine the capacity of the six key intersections in the vicinity of the Barracks under existing operating conditions using the traffic volumes collected in December 2012. The following intersections have been assessed in SIDRA 5.1 (a computer based modelling package which calculates intersection performance). - Location 1: Intersection of McMillans Road / Farrar Road; - Location 2: Intersection of Farrar Road / Brandt Road; - Location 3: Intersection of Brandt Road / Stevens Road / Campbell Road; - Location 4: Intersection of Stevens Road / McMillans Road; - Location 5: Intersection of Stuart Highway / Tulagi Road; and - Location 6: Intersection of Stuart Highway / McMillans Road.
The main performance indicators for SIDRA 5.1 include: - Degree of saturation (DoS) – A measure of the ratio between traffic volumes and the capacity of the intersection; - Average delay per vehicle – How long in seconds the average vehicle waits at the intersection; and - Level of service (LoS) – A measure of the overall performance of the intersection. The capacity of an urban road network is controlled by the throughput of traffic at intersections within that network. Average delay is commonly used to assess the actual performance of intersections, with Level of Service (LoS) used as an index. A summary of the LoS index is shown in Table 2.1.
Table 2.1 Level of service criteria for intersections Level of Average Delay| Vehicle Traffic Signals | Roundabout Give Way | Stop Signs Service (sec|veh) A Less than 14.5 Good operation Good operation Good with acceptable delays and Acceptable delays and spare B 14.5 to 28.5 spare capacity capacity Satisfactory, but accident study C 28.5 to 42.5 Satisfactory required Near capacity and accident study D 42.5 to 55 Operating near capacity required At capacity; at signals incidents will At capacity; requires other control E 55 to 70.5 cause excessive delays mode Roundabouts require other control At capacity; requires other control F >70.5 mode mode Source: Guide to Traffic Generating Developments, RMS 2002
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The existing intersection performance is summarised in Table 2.2.
Table 2.2 Intersection performance summary
Type of AM Peak hour PM Peak hour Intersection control LoS DoS Av Delay (s) LoS DoS Av Delay (s) 1. McMillans Road / Farrar Priority B 0.487 2.8 B 0.504 2.7 Road 2. Farrar Road / Brandt Road Priority A 0.202 8.4 A 0.106 8.1 3. Brandt Road / Stevens Road Priority A 0.201 8.9 A 0.247 8.3 / Campbell Road 4. Stevens Road / McMillans Priority B 0.470 2.7 B 0.488 3.2 Road 5. Stuart Highway / Tulagi Road Signals A 0.714 11.7 A 0.705 14.1 6. Stuart Highway / McMillans Signals A 0.652 14.0 C 0.908 41.4 Road Source: AECOM, 2012
Note – Level of Service for Give Way intersections is taken from the worst performing approach The results indicate that all intersections in the study area work within capacity and operate efficiently under peak conditions. The modelling indicates that in both AM and PM peak hours, all intersections have a very good level of service with acceptable average delays. In the PM peak hour, the Stuart Highway / McMillans Road intersection performs more poorly than the other key intersections, however still functions satisfactorily at LoS C and with around 90% capacity. A sensitivity analysis was undertaken on the seagull intersections of Stuart Highway / Tulagi Road and Stuart Highway / McMillans Road to assess the merging manoeuvre of the right turning traffic from the minor roads onto the Stuart Highway which in the northbound direction operates as a continuous lane. This is because SIDRA 5.1 does not take into account that the right turners need to give way to the continuous traffic flow before merging. The merge analysis shows that at both intersections the right turning vehicles from the minor road are able to merge with the Stuart Highway with minimal average delays and minimal queuing in both peak hours. 2.3.3 Mid block traffic flow Mid block traffic flows have been determined from the intersection turning counts collected at the six key intersections. Table 2.3 summarises the peak hour mid block traffic flow on the local road network surrounding Robertson Barracks. It should be noted that the midblock flows include both vehicles travelling to the Barracks as well as other local and strategic traffic.
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Table 2.3 Mid block traffic flow count AM Peak hour PM Peak hour Road Description (07:00-08:00) (16:30-17:30) NB¹ SB¹ NB SB Farrar Road Between McMillan Road and Brandt Road 370 60 70 150 Brandt Road² Between Farrar Road and Campbell Road 30 370 130 50 Stevens Road Between Campbell Road and McMillan Road 260 60 50 180 McMillans Road Between Farrar Road and Stevens Road 930 710 820 970 (E-W) McMillans Road Between Stevens Road and Stuart Highway 1100 690 660 1000 (N-S) Stuart Highway Between McMillan Road and Tulagi Road 2380 1160 1110 2160 Note - numbers have been rounded to the nearest 10
Source: AECOM, 2012
¹NB – Northbound, SB - Southbound
²The mid block traffic flows for Brandt Road were calculated using the following AM and PM peak hour periods respectively - 06:30-07:30 AM and 15:30-16:30 PM
2.4 Council data Traffic data has been obtained from Litchfield Shire Council and shows the traffic count readings of double axles per day on roads surrounding the site. This data was captured on two different occasions, and the Average Daily Traffic (ADT) is detailed in Table 2.4.
Table 2.4: Average Daily Traffic - Double axles per day - 15/02/10 to 21/02/10 and 04/07/11 to 10/07/11
ADT (average daily traffic) Road name Location 15/02/10 – 21/02/10 04/07/11 – 10/07/11
Brandt Road South of Farrar Road 1,691 Farrar Road Next to Secrett Road 4,041 Campbell Road West of Thorngate Road - 1,589 Campbell Road East of Brandt Road - 2,216 Stevens Road Near Campbell Road - 1,169 Stevens Road North of McMillans Road - 1,325 Thorngate Road North of Walby Holtze Road 455 3,998 Source: Litchfield Shire Council, 2012
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2.5 NT Government count stations Data has also been obtained from the NT Government’s Urban and Rural Primary Count Stations and has been detailed in Table 2.5. This data indicates the Average Annual Daily Traffic (AADT) on roads surrounding Robertson Barracks in 2010.
Table 2.5 AADT Figures, 2010
Location Inbound AADT Outbound AADT Total AADT McMillans Rd, 500m north of Stuart Hwy 6,977 7,817 14,794 UDVDPO21 Stuart Hwy, 400m east of Berrimah Rd 12,268 11,437 23,705 UDVDPO10 McMillans Rd, 100m south of Police Station entrance 7,327* 7,163* 14,490* UDVDCO94 Tulagi Rd, 500m south of Robertson Barracks 2,001* 1,984* 3,985* UDVDCO93 Stuart Hwy, Midway Yarrawonga & Tulagi Rd 10,319 8,014 18,333 UDVDCO79 * Data is from 2009, as 2010 information is unavailable
Source: NT Government, 2012
2.6 Existing barracks operation There are a total of approximately 4,000 personnel occupying Robertson Barracks each day, two thirds of whom are living off base (Parliamentary Standing Committee on Public Works (PWC) evidence dated 16 April 2008). Thus, there are potentially approximately 2,660 personnel travelling to/from the base on any given day. 2008 PWC evidence states that the following traffic splits represent the distribution of daily traffic to the barracks: - 17 per cent from the northern suburbs along McMillan Road; - 15 per cent from the west from Darwin CBD along Stuart Highway; and - 68 per cent from the south east from Palmerston City along Stuart Highway. 2.6.1 Barrack gate counts The main gate of the Barracks is located at Robertson Road along Thorngate Road. To cater for the peak hour demand of Defence personnel arriving and leaving the Barracks, two additional gates are open to traffic during the peak hours at Lighthorse Drive and Courage Avenue. Gate counts were obtained at the three access points to the Barracks to determine traffic activity during peak hour periods in both AM and PM peak periods. Gate counts were obtained at the locations listed below and shown in Figure 2.5. - Location 7: Intersection of Campbell Road / Lighthorse Drive; - Location 8: Intersection of Thorngate Road / Robertson Road; and - Location 9: Intersection of Thorngate Road / Courage Avenue.
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Figure 2.5 Barrier counts at Robertson Barracks
Source: Google, 2012 The counts at the temporary peak period access gates were collected between 06.15–08:00 AM and 15.30-17.30 PM for AM and PM peak hour periods respectively and gate counts at the main gate were collected over the majority of the working day (approx 06:00 AM – 18:00 PM). Table 2.6 summarises the peak hour gate counts (that coincide with the local road network peak hour) collected at the three defined access points.
Table 2.6 Peak hour gate counts at Robertson Barracks
AM Peak hour PM Peak hour Access In Out In Out Campbell Road / Lighthorse Avenue 320 n/a n/a 100 Thorngate Road / Courage Avenue 250 n/a n/a 90 Thorngate Road / Robertson Road 260 110 40 270 Note - numbers have been rounded to the nearest 10
Source: AECOM, 2012 2.6.2 Barracks generated traffic Using the gate count numbers indicated in the table above, the amount of Barracks traffic on the local road network has been determined based on the following assumptions: - Traffic originating from the north from Casuarina and its surrounding suburbs would travel along McMillans Road, Farrar Road, Brandt Road, Campbell Road and enter on Lighthorse Drive; AECOM Robertson Barracks Traffic Study 12 Defence Logistics Transformation Project (DLTP): JLU(N)
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- Traffic originating from Darwin CBD from the west would travel along Stuart Highway, McMillans Road, Stevens Road, Campbell Road and enter on Lighthorse Drive (worst case scenario); and - Traffic originating from the south east from Palmerston and its surrounding suburbs would travel along Stuart Highway, Tulagi Road, Thorngate Road and enter via Courage Avenue or Robertson Road. These assumptions are based on high level desktop analyses including shortest distance route assignment, turning count surveys and mid block flow calculations. The assumed routes are shown in Figure 2.6.
Figure 2.6 Vehicle route access to Robertson Barracks
Source: Google, 2012
Table 2.7 summarises the AM and PM peak hour traffic flows for dedicated trips to the Barracks along the local roads in the vicinity of the Barracks. The Barracks traffic as a proportion of the total traffic is also shown in the table. This is shown diagrammatically in Figure 2.7 and Figure 2.8 for the AM and PM peak hour respectively.
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Table 2.7 Dedicated traffic to / from the Barracks
AM Peak hour PM Peak hour To % of From % of To % of From % of
Barracks total Barracks total Barracks total Barracks total Farrar Road (b/w McMillans Rd and 230 61% n/a n/a n/a n/a 100 68% Brandt Rd) Brandt Road (b/w Farrar Rd and Stevens 230 61% n/a n/a n/a n/a 100 78% Rd) Stevens Road (b/w McMillans Rd and 90 34% n/a n/a n/a n/a 120 68% Campbell Rd) McMillans Road (b/w Stevens Rd and Stuart 90 8% n/a n/a n/a n/a 50 4% Hwy) Stuart Highway (west of 190 30% 50 3% 10 1% 120 23% McMillans Rd) Note - numbers have been rounded to the nearest 10
Source: AECOM, 2012 Analysis indicates that a relatively high volume of traffic is currently using Farrar Road and Brandt Road to access the Barracks in both AM and PM peak hours.
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Figure 2.7: Barracks generated traffic along the local road network in the AM peak hour
Source: AECOM, 2012
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Figure 2.8: Barracks generated traffic along the local road network in the PM peak hour
Source: AECOM, 2012
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3.0 Traffic Impact of Proposed Access Road This section details the proposed access road including the new access intersection to Robertson Barracks and its impact on the surrounding local road network and key intersections.
3.1 Proposal The feasibility of a new dedicated access road from the west of Robertson Barracks is an option being assessed. It is assumed that the gates that are currently open during the peak hours at Lighthorse Drive and Courage Avenue will no longer be required with the commissioning of the new access.
3.2 Traffic redistribution As described in Section 2.4.2 a high volume of Barracks generated traffic is currently using Farrar Road and Brandt Road to access the Barracks in both the AM and PM peak hours. It is anticipated the proposed new access road will relieve the traffic flow currently observed on Farrar Road and Brandt Road by redirecting it to McMillans Road. It has been assumed all dedicated traffic to / from the Barracks that currently uses Brandt Road, Farrar Road and the Stuart Highway (to the west of McMillans Road) would use the new access at Stevens Road / McMillans Road intersection to access the Barracks. It has been assumed that traffic entering and exiting the Barracks from the accesses along Tulagi Road would continue to use the main access as shown in Figure 3.1.
Figure 3.1: Redistribution of Barracks traffic
The AM and PM peak hour traffic flows for dedicated trips to the Barracks along the local roads in the vicinity of the Barracks after redistribution due to the new access road is shown in Table 3.1.
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Table 3.1 Redistribution of dedicated traffic to / from the Barracks
AM Peak hour PM Peak hour Location To Barracks From Barracks To Barracks From Barracks Farrar Road (b/w McMillans Rd and 0 n/a n/a 0 Brandt Rd) Brandt Road (b/w Farrar Rd and Stevens 0 n/a n/a 0 Rd) Stevens Road (b/w McMillans Rd and 420 n/a 10 220 Campbell Rd) McMillans Road (b/w Stevens Rd and 230 n/a n/a 100 Farrar Rd) McMillans Road (b/w Stevens Rd and 190 n/a 10 120 Stuart Hwy) Stuart Highway (west of McMillans Rd) 190 50 10 190 Note - numbers have been rounded to the nearest 10
Source: AECOM, 2012 Mid block flows identified in Section 2.3.3 from the intersection counts collected have subsequently changed due to the redistribution of dedicated Barracks traffic. Table 3.2 summarises the existing and revised mid block traffic flow on the local road network surrounding Robertson Barracks.
Table 3.2 Difference between original and revised mid block traffic flow count AM Peak hour PM Peak hour Road Description (07:00-08:00) (16:30-17:30) Base case NB¹ SB¹ NB SB Farrar Road Between McMillan Road and Brandt Road 370 60 70 150 Brandt Road² Between Farrar Road and Campbell Road 30 370 130 50 Stevens Road Between Campbell Road and McMillan Road 260 60 50 180 McMillans Road Between Farrar Road and Stevens Road 930 710 820 970 (E-W) McMillans Road Between Stevens Road and Stuart Highway 1100 690 660 1000 (N-S) Stuart Highway Between McMillan Road and Tulagi Road 2380 1160 1110 2160 With additional access Farrar Road Between McMillan Road and Brandt Road 150 60 70 50 Brandt Road² Between Farrar Road and Campbell Road 30 140 30 50 Stevens Road Between Campbell Road and McMillan Road 580 60 60 280 McMillans Road Between Farrar Road and Stevens Road 930 940 840 970 (E-W) McMillans Road Between Stevens Road and Stuart Highway 1200 690 670 1070 (N-S) Stuart Highway Between McMillan Road and Tulagi Road 2380 1060 1110 2150 Difference
Farrar Road Between McMillan Road and Brandt Road -220 0 0 -100 Brandt Road² Between Farrar Road and Campbell Road 0 -230 -100 0 Stevens Road Between Campbell Road and McMillan Road +320 0 +10 +100
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McMillans Road Between Farrar Road and Stevens Road (E-W) 0 +230 +20 0 McMillans Road Between Stevens Road and Stuart Highway (N-S) +100 0 +10 +70 Stuart Highway Between McMillan Road and Tulagi Road 0 -100 0 -10 Source: AECOM, 2012
¹NB – Northbound and SB - Southbound
²The mid block traffic flows for Brandt Road were calculated using the following AM and PM peak hour periods respectively - 06:30-07:30 AM and 15:30-16:30 PM The table shows that with the redistribution of Barracks generated traffic to the new access road off Stevens Road there is a reduction in the amount of Barracks traffic using Brandt Road and Farrar Road as a route to the Barracks. There has been a subsequent increase of Barracks traffic on Stevens Road (albeit only briefly before the Barracks traffic would turn into the access road) and McMillans Road as these roads are the main routes to the new access road.
3.3 Intersection performance The key intersections on the local road network surrounding the Barracks has been reassessed for the AM and PM peak hour using the redistributed traffic flows, with the exception of the Stevens Road / McMillans Road intersection which will form the new access intersection to the Barracks which is discussed in Section 3.4 below. The existing intersection layouts and control types have remained unchanged from the existing intersection analysis and each intersection has been modelled in the same way as previously (as discussed in Section 2.3.2). Table 3.3 shows the peak hour intersection performance of the key intersections.
Table 3.3 Intersection performance summary with traffic redistributed AM Peak hour PM Peak hour (07:00-08:00) (16:30-17:30) Intersection LoS DoS Av Delay (s) LoS DoS Av Delay (s) 1. McMillans Road / Farrar Road B 0.487 1.7 B 0.504 1.2 2. Farrar Road / Brandt Road¹ A 0.076 8.4 A 0.031 7.9 3. Brandt Road / Stevens Road / Campbell Road¹ A 0.105 8.4 A 0.061 7.9 5. Stuart Highway / Tulagi Road A 0.714 11.5 A 0.705 14.1 6. Stuart Highway / McMillans Road A 0.580 13.6 C 0.904 40.2 Source: AECOM, 2012
Note – Level of Service for Give Way intersections is taken from the worst performing approach The results indicate that across all intersections, there was no major change to level of service, degree of saturation or average delay from the existing conditions. As expected, the intersections of Farrar Road / McMillans Road, Farrar Road / Brandt Road and Brandt Road / Stevens Road / Campbell Road have improved intersection performance results experiencing shorter average delays and greater spare capacity under the redistributed traffic flows. This is due to the majority of Barracks traffic now concentrated at the intersection of McMillans Road / Stevens Road.
3.4 Barracks Access Options 3.4.1 New McMillans Road / Stevens Road Intersection – Option 1A One of the proposals for a new access road to the Barracks will originate from the intersection of McMillans Road / Stevens Road. The existing intersection is shown in Figure 3.2.
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Figure 3.2: Existing intersection layout of Stevens Road / McMillans Road
Two indicative intersection layout options are recommended which are as follows and are shown in Figure 3.3 and Figure 3.4: 1) The new access road would form a priority controlled ‘seagull’ T-intersection with McMillans Road, with Stevens Road realigned to intersect with the new access road. The left slip from McMillans Road would be reconfigured to a standard left turn lane. Under the redistributed flows, the amount of traffic on Stevens Road reduces significantly and would form a minor approach to the access road (hence its realignment from the main intersection). 2) The new access road would form the fourth approach of a single lane roundabout intersection configuration with McMillans Road and Stevens Road. It must be noted that the recommended intersection layouts are indicative only and the concept and detail design of the intersection is subject to further traffic analyses.
Figure 3.3: Indicative layout option 1
Source: AECOM, 2012 AECOM Robertson Barracks Traffic Study 20 Defence Logistics Transformation Project (DLTP): JLU(N)
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Figure 3.4: Indicative layout option 2
Source: AECOM, 2012 The indicative intersection layouts have been assessed using SIDRA 5.1 to determine the intersection performance under each layout. Table 3.4 summaries the intersection performance of the intersection under the two layouts in the AM and PM peak hour.
Table 3.4: New access intersection performance AM Peak hour PM Peak hour (07:00-08:00) (16:30-17:30) New access road / McMillans Road LoS DoS Av Delay (s) LoS DoS Av Delay (s) Layout 1 – Priority controlled T intersection B 0.47 4.7 B 0.488 4.0 Layout 2 – Roundabout A 0.763 11.4 A 0.580 10.3 Note – Level of Service for Give Way intersections is taken from the worst performing approach The table indicates that under a priority controlled T-intersection layout the intersection would have approximately 60% spare capacity in the AM and PM peak hours and with average delays of less than 5 seconds. In both peak hours the right turns into the access road from McMillans Road and out of the access road onto McMillans Road perform at LoS B (the worst performing movements). Under a roundabout layout configuration the intersection performs well at LoS A in both the AM and PM peak hour and with minimal average delays. There is approximately 25% and 40% spare capacity experienced in the AM and PM peak hours respectively. 3.4.2 New McMillans Road Intersection – Option 1B Another option is to create a new intersection at a midpoint location on McMillans Road between Stevens Road and the Stuart Highway to accommodate the new access road to the Barracks. Analysis shows that the new intersection would work as a priority controlled T-intersection with short turn lanes on every approach (indicatively approx 100m in length), as shown in Figure 3.5. To improve the efficiency of the right turn traffic from the Barracks and to reduce the average delay on this approach, the intersection could be designed as a seagull intersection enabling the right turn traffic to wait in the median before merging with the northbound traffic along McMillans Road. The layout would be similar to that already experienced at the Stevens Road / McMillans Road intersection.
AECOM Robertson Barracks Traffic Study 21 Defence Logistics Transformation Project (DLTP): JLU(N)
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Figure 3.5: Indicative layout for new access intersection along McMillans Road
Source: AECOM, 2012 It must be noted that the recommended intersection layout is indicative only and the concept and detail design of the intersection is subject to further traffic analyses. 3.4.3 Upgrade of Lighthorse Drive access point – Option 2 Another option is to upgrade the temporary access of Lighthorse Drive (accessed via Campbell Road) to a permanent access. In this option, a new western access road has not been considered. Under this proposal access currently allows entry only in the AM peak period and exit only in the PM peak period. The access will become two-way in both peak periods if made permanent. For the purpose of analysis it has been assumed that 20% of Barracks generated traffic that currently exits the main gate in the AM peak hour will transfer to the Lighthorse Drive intersection, with the reverse occurring in the PM peak hour. Analysis indicates that the access intersection of Lighthorse Drive will perform well as a four-way priority controlled intersection, with minimal average delays and significant spare capacity in both peak hours. There are currently right turn bays of approximately 165m and 120m from Campbell Road into Lighthorse Drive and the unnamed road opposite Lighthorse Drive respectively, as shown in Figure 3.6.
AECOM Robertson Barracks Traffic Study 22 Defence Logistics Transformation Project (DLTP): JLU(N)
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Figure 3.6: Indicative layout for permanent access on Campbell Road
Source: AECOM, 2012 It must be noted that the recommended intersection layout is indicative only and the concept and detail design of the intersection is subject to further traffic analyses. 3.4.4 Upgrade of Main Gate access point – Option 3 Another option is to upgrade the Main Gate access point so that there is no requirement for the temporary accesses at Lighthorse Drive and Courage Avenue. A new western access road has also not been considered in this option. The current intersection layout of the main gate access (Robertson Road / Thorngate Road intersection) is a priority controlled T-intersection that includes a separate left turn lane of approximately 90m from Thorngate Road into the Barracks. Analysis indicates that the intersection performs well in both peak hours, with minimal average delays and significant spare capacity under the following indicative layout shown in Figure 3.7. The intersection remains as existing except for the addition of a short right turn lane on Thorngate Road (approx 50m) into the Barracks to accommodate Barracks generated traffic turning right, especially in the AM peak hour.
AECOM Robertson Barracks Traffic Study 23 Defence Logistics Transformation Project (DLTP): JLU(N)
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Figure 3.7: Indicative layout for Main Gate access on Thorngate Road
Source: AECOM, 2012 It must be noted that the recommended intersection layout is indicative only and the concept and detail design of the intersection is subject to further traffic analyses.
3.5 Barrier Access Requirement An assessment of how many barriers (lanes) are required for each option has been undertaken. 3.5.1 Option 1a and 1b – New access road Based on the number of vehicle entries and exits expected to occur at the new access to the Barracks during the peak hours, 2 barriers are required in the inbound direction with storage for a minimum of 8 vehicles in both lanes. 1 barrier is required in the outbound direction with storage for a minimum of 3 vehicles. 3.5.2 Option 2 – Upgrade Lighthorse Drive access Based on the number of vehicle entries and exits expected to occur at the upgraded access to the Barracks on Lighthorse Drive during the peak hours, 2 barriers are required in the inbound direction with storage for a minimum of 5 vehicles in both lanes. 1 barrier is required in the outbound direction with storage for a minimum of 3 vehicles. 3.5.3 Option 3 – Upgrade of Main Gate access point Based on the number of vehicle entries and exits expected to occur at the upgraded access to the Barracks on Lighthorse Drive during the peak hours, more than 2 barriers are required in the inbound direction due to the high amount of Barracks traffic expected during the AM peak period. 2 barriers are required in the outbound direction with storage for a minimum of 11 vehicles in each lane. AECOM Robertson Barracks Traffic Study 24 Defence Logistics Transformation Project (DLTP): JLU(N)
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4.0 Summary and conclusion
4.1 Summary AECOM, via Trapp Architects, has been commissioned by the Department of Defence to prepare a traffic study in association with vehicular access at Robertson Barracks, Northern Territory. A new western access road is proposed to be constructed at the intersection of Stevens Road and McMillans Road as part of the DLTP JLU(N) project. Existing traffic counts at key intersections on the local road network have been obtained in order to determine the existing traffic conditions on the local road network and performance of the key intersections. Analysis of the existing situation indicates that all intersections in the study area work within capacity and operate efficiently under peak conditions. Counts have also been obtained at the three main access gates to the Barracks in order to determine the amount of Barracks generated traffic on the local road network. Based on a set of travel pattern assumptions, analysis indicates that a significant amount of Barracks traffic uses Brandt Road and Farrar Road to access the Barracks via the northern gate (Lighthorse Drive) off Campbell Road during the AM and PM peak. With the proposed construction of a new western access road to the Barracks at the intersection of Stevens Road and McMillans Road, the Barracks generated traffic that has been redistributed on the local road network. The analysis indicates a decrease in the amount of Barracks traffic on Brandt Road and Farrar Road and the intersections along this route perform more adequately. There is a negligible impact to all other key intersection performance on the local road network once Barracks generated traffic is redistributed. Two indicative intersection layouts are recommended at the intersection of Stevens Road and McMillans Road to incorporate the new access road; a priority controlled T-intersection and a roundabout configuration. Both layouts perform adequately with minimal average delays and spare capacity in both peak hours when a large amount of Barracks generated traffic is concentrated at this intersection. Other options to accommodate Barracks generated traffic have also been looked at which do not consider the construction of a new access road. The other options include upgrading the temporary access on Lighthorse Drive to a permanent access that allows both entries and exits and upgrading the Main Gate access on Robertson Road to accommodate all Barracks generated traffic throughout the day. Both options have been found to be feasible. The additional Barracks generated traffic as a result of the proposed JLU(N) precinct is negligible.
4.2 Conclusion The traffic study indicates that the construction of a new access road to Robertson Barracks would reduce the amount of Barracks traffic on the local roads of Farrar Road and Brandt Road on the surrounding road network, without compromising the performance of other key intersections and local roads within the study area. Two options of a new intersection at McMillans Road are recommended which will both perform with minimal average delays and spare capacity in both peak hours. Discussion with 1 Brigade to confirm and refine the assumptions for the future Barracks operation is required.
C:\DLTP-4\Traffic\Robertson Barracks - Transport Study_25012012 MJ.docx Revision 0 - 23 January 2012 AECOM Robertson Barracks Traffic Study Defence Logistics Transformation Project (DLTP): JLU(N)
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Appendix A
Council Traffic Data
C:\DLTP-4\Traffic\Robertson Barracks - Transport Study_25012012 MJ.docx Revision 0 - 23 January 2012 AECOM Robertson Barracks Traffic Study A-1 Defence Logistics Transformation Project (DLTP): JLU(N)
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Appendix A Council Traffic Data
C:\DLTP-4\Traffic\Robertson Barracks - Transport Study_25012012 MJ.docx Revision 0 - 23 January 2012 AECOM Robertson Barracks Traffic Study Defence Logistics Transformation Project (DLTP): JLU(N)
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Appendix B
Robertson Barracks Access Gate Counts
C:\DLTP-4\Traffic\Robertson Barracks - Transport Study_25012012 MJ.docx Revision 0 - 23 January 2012 AECOM Robertson Barracks Traffic Study B-1 Defence Logistics Transformation Project (DLTP): JLU(N)
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Appendix B Robertson Barracks Access Gate Counts
C:\DLTP-4\Traffic\Robertson Barracks - Transport Study_25012012 MJ.docx Revision 0 - 23 January 2012