Intersection and Upgrade Design Philosophy Statement

Level 4, 18 London Street PO Box 9041, Hamilton 3240

New Zealand

Phone +64 7 838 0144 Email [email protected] Web www.bbo.co.nz

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MEMO

TO: Robin Walker

FROM: Caleb McCarthy

DATE: 10 February 2020 JOB NO. 146470

SUBJECT: C2/C3 Cambridge Road Intersection and Upgrade Design Philosophy Statement

1. Introduction

Waipa District Council (WDC) approved a new structure plan covering three new urban growth areas (C1 and C2/C3) within the township of Cambridge. This structure plan provides a proposed layout for the urban development of these areas along with general requirements to meet community, infrastructure and design outcomes for any future subdivisions within the growth cells.

The transportation network developed as part of the structure planning process identified a number of key road links and junctions to be delivered as part of the proposed transport network in this area. One of the key elements within the network is a new intersection on Cambridge Road between the C2 and C3 growth cells (henceforth referred to as the ‘C2/C3 Cambridge Road Intersection’).

Purpose of Memorandum

This memorandum has been produced as a brief Design Philosophy Statement for the following purposes:

• Document the assumptions that have been made within the developed design of the proposed

intersection

• Document the standards and assumptions that will apply to the development of the Detailed

Design of the C2/C3 Cambridge Road Intersection

• Provide an early outline of key features that will require additional consideration or could become

a project risk or constraint during the detailed design phase

Scope

This memorandum is based on the following project scope:

i) Design of a new signalised intersection on Cambridge Road

ii) Design of a new collector road approximately 50m north (Collector Road 1) of the intersection

and approximately 700m to the south (Collector Road 4)


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iii) Widening of Cambridge Road to accommodate the new cross section including cycle facilities,

stormwater treatment and the new intersection

iv) Preservation of existing trees adjacent to Cambridge Road

2. Design Standards and Assumptions

All design is based on:

• Waikato Regional Infrastructure Technical Specifications (RITS) and relevant documents

referenced therein

• Austroads Guide to Road Design (AGRD)

• Standards New Zealand documents

• NZTA technical specifications and memoranda

• CROW Design Manual of Bicycle Traffic

To date, there are no approved departures from these standards, however, should any be necessary, the departures will go through the appropriate WDC channels.

Earthworks Design

Earthworks will be in accordance with the RITS. The developed design principal includes typical cut and fill batters of 3:1 or flatter where possible. Some areas may be steeper where required to avoid spill over and are noted on the drawings. The detailed design will ensure appropriate geotechnical engineering design is applied to any lare cuts and fills. The earthworks design will also be in compliance with the relevant resource consents (if any) from Waikato Regional Council.

Stormwater Design

Bulk stormwater design for the wider Cambridge Urban Growth Areas is being undertaken by others. The design of this intersection will allow for appropriate water quality treatment and conveyance/ reticulation of the primary design storm. Attenuation and flood mitigation are required these works. The design of all infrastructure will be in accordance with the RITS requirements for:

• Design life;

• Design Events;

• Collection and conveyance systems;

• Drainage structures;

• Overland flow paths.


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Stormwater is currently proposed to be treated through a series of rain gardens and/or treatment swales. From these devices, stormwater runoff will be conveyed through a reticulated network to the Central Outlet Pipelines which is designed by WSP. Coordination between projects and key stakeholders will be required throughout the detailed design to ensure positive stormwater outcomes are achieved. Some of the key items requiring consideration are discussed in Section 3.

Geometric Design

All design is in accordance with the RITS requirements. Traffic volumes are discussed in memo Summary of Predicted Volumes and Performance Modelling in Appendix A. Table 2.1 outlines the design parameters and assumptions used:

Table 2.1 – Geometric Design Parameters

Parameter Value and Standard Notes

Design Speed 60 km/h Cambridge Road

50 km/h Collector Roads

Sight Distance

2.0 sec reaction time and 0.36 coefficient of longitudinal deceleration as per AGRD desirable values

Minimum desirable values may be considered where there may be significant benefits as a result

Design Vehicles 18 m semi-trailer with minimum 0.6 m clearance (wheel track to kerb and body to furniture) as per RTS 18

Including vehicle to vehicle clearances for opposing turning movements

Horizontal Alignment As per RITS (and AGRD referenced therein).

Superelevation is not proposed on the new design, however, will likely be required at the tie in of Cambridge Road

Vertical Alignment As per RITS (and AGRD referenced therein)

Intersection form Raised platform with signals

Platforms will follow guidelines from VicRoads RDN 03-07 and lessons learnt from local implementation examples of raised intersections


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Table 2.2 below outlines the proposed cross section parameters.

Table 2.2 – Cross Section Dimensions

Element

Proposed Dimension

Cambridge Road Collector Road

Shoulders 2.0 m 2.0 m

Traffic Lanes 3.5 m 3.5 m

Median 2.0 m minimum1 None2

Paths 3.0 shared & 1.5 m

pedestrian3 3.0 m shared on both sides

Berms 2.5 m min berm/ stormwater 2.5 m berm/parking provision

Crossfall 3.0% Normal 3.0% Normal

Note 1: 3.5m minimum for staggered pedestrian crossings

Note 2: 3.0 m to be provided for turn bays as required

Note 3: Shared on south side of Cambridge Road carriageway and 3.0 m shared on both sides around intersection

A number of geometric features will need additional consideration and coordination within the detailed design phase. These items are discussed further in Section 3.

Pavement and Surfacing

The philosophy for the Developed Design was to provide for an overlay design on the Hamilton bound lanes where possible. The intersection could be either a structural asphalt or a bound aggregate makeup. During the Developed Design phase pavement pits were undertaken along the corridor length to help inform the pavement design. Consideration of pavement types and design will be undertaken during the detailed design following interpretation of pavement test pits and the historical FWD data.

Traffic Services

All traffic services will be designed in accordance with RITS requirements and the relevant standards referenced within. Lighting – It is anticipated that lighting will be located on both sides of the road at regular intervals and will include the use of joint use signal poles. A lighting design will be undertaken by a specialist Lighting Engineer to confirm assumptions and efficiency during detailed design.


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Signs and Markings – All signs and markings will be in accordance with the relevant RITS and NZTA standard. During detailed design there will need to be coordination with adjacent projects and WDC regarding signage strategies. Safety barriers – May be required adjacent to the existing gully on Cambridge Road and on any areas with non-recoverable slopes. A detailed assessment of if safety barriers are required will be undertaken as part of the detailed design phase. Should barriers be required; they will be designed in accordance with NZTA m23 requirements. Traffic Signals – Will be designed in accordance with relevant sections of the RITS and the National Traffic Signal Specifications referenced therein.

Wastewater Drainage and Water Reticulation

Wastewater and water reticulation are not included within the scope of works. Should any existing infrastructure require relocation to accommodate the works, the design of these relocations will be in accordance with RIST requirements.

3. Other Features

The Developed Design phase has identified some proposed features that require further consideration during detailed design, requiring input and coordination with relevant stakeholders, adjacent developers and WDC. These specific features are discussed in this section.

Cycle on/off Ramps

On all approaches and exits from the signalised intersection the layout will include links between the shared path and sealed shoulder. On the north/south collector road the proposed structure plan includes future roads and the relocated access to the Te Awa Lifecare facility. These connections limit the available location for the ramps. Of specific interest are:

• Southbound approach (off ramp): Conflict area due to proximity of future road (structure plan)

• Southbound departure (on ramp): Conflict area due to Te Awa access (right turn bay), and future

road (structure plan)

Both links are shown indicatively on the plans, however, all areas of conflict will be considered during detailed design to minimise the risk and improve safety as much as practicable.

Mature Trees

Several mature trees are located along the Cambridge Road corridor, of which a preference has been noted to keep as many as practicable. It does not appear practical to completely avoid these trees with the proposed footprint – in some cases the dripline of the trees sits within the road carriageway.


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One, or a combination of the following options is proposed to preserve the trees:

• Lower the berm below the road profile – Detailed design will need to consider overland flow

paths, particularly around the intersection itself as the paths will need to be at road level to

provide pedestrian crossing facilities.

• Form a boardwalk system over the tree roots – Once again there will need to be consideration of

overland flow paths and the method in which the boardwalk is designed and constructed in order

to protect the trees.

• Lower the road profile and adopt a complete pavement reconstruction construction as opposed

to an overlay.

Existing Gully

An existing gully is located approximately 350m west of the proposed signalised intersection. With the proposed typical cross section, currently the design would require the gully to be filled. As such, the developed design suggests reducing the berm width in this area. Detailed design will need to consider the following:

• If the horizontal and/or vertical geometry can be adjusted to ensure the gully has minimal

influence on the cross section.

• Survey of the area to confirm proximity of design to the gully

• Geotechnical suitability of filling close to the gully

• Possible requirement for a retaining wall

• Safety in design factors such as construction near the gully, maintenance and inspection

requirements and safety for road and path users.

Possible location and design of safety from falling fence or road safety barrier

Service Lane

A service lane is located west of the existing gully on Cambridge Road. Any design affecting either of the two access points will have the following considerations:

• Potential need to upgrade or reconstruct the existing accesses

• Designing a geometrically suitable access for both ingress and egress

• The practicality and option of constructing a new single access point

• Coordination and liaison with the relevant parties

Mid-block Crossings

Council have expressed interest in two mid-block crossings on Cambridge Road. The location and details of the crossing have not been finalised; however, the detail design process will include the following considerations:

• Proximity to merge and diverge of traffic lanes, including allowance for any advanced warning


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• Type of crossing (courtesy/zebra/signalised crossing)

• Staggered crossing where practicable

• Speed management (raised platforms or similar)

Coordination with Adjacent Projects

To date, there has been coordination with the designers of the Central Outlet Pipelines. As both projects progress into detailed design, there will need to be careful consideration from both parties to ensure a positive resulting outcome. It is understood that some of the adjacent land, both north and south of the intersection is to be developed in the near future. Detailed design will aim to ensure that the road and earthworks levels of adjacent developments are well coordinated including the locations of intersections and potential service connections.

4. List of Drawings

The drawings produced in the Developed Design phase are: - 146470-00-0220 Overview Plan

- 146470-00-0221 Cambridge Road General (RS-100) Arrangement Plan and Long Section sheet 1




- 146470-00-0226 Collector Road 1 & 4 (RS-200) General Arrangement Plan and Long Section sheet 1



- 146470-00-0231 Cambridge Road (RS-100) Typical Cross Sections sheet 1



- 146470-00-0234 Collector Road 1 & 4 (RS-200) Typical Cross Sections sheet 1

- 146470-00-0236 Signalised Intersection Layout

- 146470-00-0241 Stormwater Plan


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5. Appendix A

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TO: Robin Walker (Waipa District Council)

FROM: Renata Gomez REVIEWED / APPROVED Cameron Inder

DATE: 10 February 2020 JOB NO. 146470

SUBJECT: C2/C3 Cambridge Road Intersection and Upgrade – Summary of Predicted Volumes and Performance Modelling

1. Introduction

Bloxam Burnett and Olliver Ltd (BBO) have been commissioned by Waipa District Council (WDC) to undertake the detailed design of the future new intersection on Cambridge Road, known as the C2/C3 intersection. The intersection is a part of C2/C3 Cambridge Growth Cell development. As a part of that work BBO has undertaken a traffic prediction, distribution and capacity analysis of the intersection to inform the overall design. This is a summary of that assessment, which focuses on the design year of 2041. Figure 1 on the following page shows the locality of the intersection and our assessment of the likely preferred travel route options within the area (source: WDP Cambridge C1 and C2/C3 Structure Plan).

2. Expected Traffic Volumes

2.1. Mode Share Target

WDC requested consideration for all modes of transport in the calculations of the predicted traffic volumes and trip distribution at the C2/C3 intersection. This includes trips by active modes (pedestrians, cyclists and “active mobility” such as e-scooters), public transport (PT) and private vehicles. Table 2 indicates the different mode share targets, where the “Expected Share” is what WDC considers as readily achievable, while the “Aspirational Share” is the level that Council is targeting to achieve by 2041 through education and cumulative infrastructure investment. For clarity, the mode share is the percentage of trips using a particular type of transportation mode.

Table 1: Mode Share Target

2041 Mode of Transport Expected Share (%)

Aspirational Share (%)

Active Mode 10 20

PT Internally 5 10

PT Externally 10 15

Private Vehicles 75 55

Total Trips 100 100

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Figure 1: Intersection Locality and Likely Preferred Route Options

The “expected” mode share can be considered the worst-case scenario as it relates to a higher proportion of people choosing private vehicles as their normal means of transportation.

However, the intersection performance analysis was conducted on both the expected and aspirational mode shares so WDC can understand how the intersection responds to change.

2.2. Trip Generation at C2/C3 intersection

The turning movement traffic volume calculations for the C2/C3 intersection considered:

• The expected 2041 volume of traffic travelling on Cambridge Road. This was based on existing traffic volumes with a growth rate applied (1.5% per annum).

• Its locality and likely preferred route options for vehicles traveling to/from C1, C2 and C3 Growth Cells.

The indicative road layout shown in Figure 1 provides a visual understanding of the convenient travel route options that will exist in the area. The various alternative route options available to the C1, C2 and C3 Growth Cells means that only a portion of the traffic generated by each is likely to travel through the intersection on a daily basis in the peak periods. The resulting estimated contribution of vehicle trips using the C2/C3 intersection from each cell is detailed in Table 2 below.

C2/C3 Intersection

C1 Cell

Te Awa Lifecare Development St Peter School

Pe

ak R

d

C3 Growth Cell

C2 Growth Cell

N

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Table 2: Expected Share of Vehicle Trips using C2/C3 Intersection by Growth Cell

Traffic To/From

Proportion of Vehicle Trips Using C2/C3 Intersection

Comment Expected

(%)

Sensitivity Test* (%) Origin/Destination

C1 10 10 Residential More logical route options provided

C2

30 50

Residential Equally attractive route options provided

30 50

School1 Equally attractive route options provided

C3

50 75 St Peter &

Chartwell Equally attractive route options provided

100 100 Te Awa Lifecare No other option provided for Te Awa residents

*worst-case scenario

A sensitivity test was undertaken as shown by the third column of Table 2. This is common practice for prediction modelling and aims to provide a “what if” conservative analysis of intersection performance. The resulting 2041 AM and PM peak hour sensitivity movement volumes are below:

2041 AM Peak Hour - Sensitivity

1 A new school is proposed under the Waipa District Plan in the C2 Growth Cell – location to be confirmed.

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2041 PM Peak Hour - Sensitivity

3. Intersection Performance

3.1. Traffic Analysis

Level of Service (LoS) is a qualitative measure, ranked from A (free flow conditions) to F (severe congestion), that is used to describe operational conditions experienced by vehicular and pedestrian traffic. to. SIDRA modelling software was used to assess the intersection performance in terms of LoS and average delay to users.

LoS D is considered a practical upper limit in for the overall performance of a signalised intersection. It is effectively a level where there is a balance achieved between operational efficiency and efficient use of public funds and resources in relation to the cost and size of the intersection. Figures 2 to 7 in Appendix indicate the LoS expected in 2041 at this intersection in the AM and PM peaks for the three different scenarios tested below:

• 2041 Expected Mode Share (ExpMS)

• 2041 Aspirational Mode Share

• 2041 ExpMS + Sensitivity Test.

According to the analysis (refer to Figures 1 to 5 in Appendix), LoS C and D are expected for most traffic movements through the intersection. LoS E, (> 55s and <80s delay per vehicle) is only experienced in the right-turn movements during PM peaks, for both the expected and aspirational mode share scenarios. The maximum average delay expected in these movements is 59 seconds per user. This delay is considered acceptable given that the cycle time of the signal intersection is up around 90s and

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the queue lengths for the right turn movements are fully retained within the storage length of the lanes.

These sensitivity tests (refer to Figure 6 and 7) were conducted in conjunction with the ExpMS. They include a higher portion of traffic from C2 and C3 Growth Cells travelling via the intersection and a higher portion of people traveling via private vehicles.

The sensitivity tests indicate LoS E are expected on four different movements in the AM and PM peaks. The maximum average delay expected in these movements is 77 seconds per vehicle. This delay is also considered acceptable given it is experienced only by the right turn movements from Cambridge Road, and the queues for these are retained within the storage length of the right turn lanes.

The intersection layout that produced the above LoS results and forms the basis of the final design, is shown below:

3.2. Active Mode Analysis

This analysis refers to the expected average delay experienced by active mode users such as pedestrians, cyclists and active mobility users.

As a result of the traffic distribution and volume predictions described earlier, the intersection performance of LoS D is achieved with the Cambridge Road and side road pedestrian crossings being treated as single stage signal crossings. I.e. Users do not need to stop on an island in the middle of the road and wait for another signal crossing.

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The typical maximum delay experienced by active modes using the signal crossings consists of a situation where a pedestrian wishes to travel from one corner of the intersection to the opposite corner, or vice versa. This requires the crossing of two of the four legs of the intersection, involving two signal crossings.

The average maximum delay expected on this basis, is shown in Table 3. The maximum average delay expected is 69 seconds per pedestrian, (i.e. just over one minute). This level of delay is considered non-critical as it is typically shorter than the overall signal cycle time. Therefore, it is not expected to cause frustration and unsafe behaviour such as active mode users crossing without waiting for the green walk signal.

Table 2: Maximum Pedestrian Average Delay

Analysis Scenario Maximum Average Delay Expected

(second)

2041 AM - ExpMS 52.5

2041 PM – ExpMS 57.7

2041 AM – Aspirational Mode Share 48.5

2041 PM – Aspirational Mode Share 51.5

2041 AM – ExpMS + Sensitivity Test 61.5

2041 PM - ExpMS + Sensitivity Test 68.6

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Appendix

SIDRA Results

Lane Level of Service Summary

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Key:

Figure 2: 2041 AM - ExpMS

Figure 3: 2041 PM - ExpMS

Figure 4: 2041 AM - Aspirational Mode Share

Figure 5: 2041 PM - Aspirational Mode Share

Figure 6: 241 AM - ExpMS + Sensitivity Test

Figure 7: 2041 PM - ExpMS + Sensitivity Test

Documents

Intersection and Upgrade Design Philosophy Statement