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Signals on Arterials

In document Liveable Neighbourhoods (Page 37-40)

Typical Streets

Case 3: Home-based business generates visitor parking demand and should have 7.2 metre wide streets as recommended for commercial use

4.3 Signals on Arterials

Main Roads has control over signal installation and operation in Western Australia. Traffic signal warrants include vehicle volumes, crash history

and pedestrian volumes. Please refer also to Austroads Guide to Traffic Engineering Practice: Part 5, Intersections At-Grade.

Proposals that contemplate intersection control using traffic signals should be discussed with Main Roads at an early stage.

At the development planning stage it is important to identify existing signal locations and establish appropriate spacing to any new signalised intersections. There are no established spacing guidelines published for use in Western Australia.

Austroads Guide to Traffic Engineering Practice: Part 5 (page 10) indicates 350–550m between signalised intersections to facilitate co-ordination, but current practice by Main Roads is to seek greater spacing if possible. When planning the interconnected street system of Liveable Neighbourhoods it is expected that arterial/arterial type intersections will be encountered approximately every 1.5–2.0 kilometres.

Between these intersections, circumstances may require an ‘intermediate’

signalised intersection due to traffic volumes and safety issues at Neighbourhood Connector/Arterial intersections. At these ‘intermediate’

signals, T-junction or 4-way configurations will operate safely. At the remaining intersections (un-signalised), 4-ways may operate safely but are not encouraged. Priority controlled T-junctions are expected to be more generally appropriate.

Please refer also to Chapter 2, Street Layout Guidelines that discuss access onto arterials.

Intersection Control Guidelines

Page 32

Table 5: TRAFFIC CONTROL AT 4-WAY INTERSECTIONS

Intersection Type Signals Roundabout Stop/Give Way

Arterial/Arterial Yes Yes (high capacity roundabout in low pedestrian/

cyclist activity environment)

No Arterial/Neighbourhood Connector

(Few 4-ways at these junctions)

Yes (if warrants are satisfied)

Yes, if signal co-ordination is not important, but inappropriate if there are significant pedestrian flows

No Neighbourhood Connector /

Neighbourhood Connector

No Yes (10–12 m inner island diameter designed for slow speeds is more suitable for pedestrians/cyclists)

Rarely (refer to special guidelines in Section 4.6)

Neighbourhood Connector / Access Street (Special intersection control review required)

No Occasionally, for speed control and intersection safety on Neighbourhood Connectors (refer to Section 4.4)

Yes (refer to special guidelines in Section 4.6)

Access Street / Access Street No Rarely (refer to Appendix B, Issue 3) Yes

Table 6: TRAFFIC CONTROL AT T-JUNCTIONS

Intersection Type Signals Roundabout Stop/Give Way

Arterial/Arterial Yes Yes (high capacity roundabout and low pedestrian/

cyclist activity)

No Arterial/Neighbourhood Connector

(Few 4-ways at these junctions)

Occasionally (if warrants are satisfied)

Yes, if signal co-ordination is not important, but may not be appropriate if there are significant pedestrian flows

Yes, depending on volumes and nearby signals as alternative access Neighbourhood Connector /

Neighbourhood Connector

No Yes (10–12 m inner island diameter). Used for speed control benefits even if volumes are acceptable

Yes, but can use roundabout control where speed control is needed on major street

Neighbourhood Connector / Access Street

No Occasionally, for speed control and intersection safety on Neighbourhood Connectors (refer to Section 4.4)

Yes

Access Street / Access Street No Rarely (refer to Appendix B, Issue 3) Yes

N

Signals will be used at most intersections of Arterials. In some cases, high capacity roundabouts (e.g. inner island diameter 20 m +) will be used but these are not suitable in areas of high pedestrian and cyclist activity (e.g Town Centre).

Figure 11 Intersection Control to Match Intersection Type

Integrator 'A'

Integrator 'B'

Priority control (give-way/stop on the minor leg) is appropriate for most if not all 4-way intersections of Access Streets if leg lengths (run up) are kept short.

4-way intersections between Access Streets and Neighbourhood Connectors will require special evaluation to ensure safe priority control operation. Traffic volumes including the percentage of traffic crossing the Neighbourhood Connector will influence the appropriate control method. If unsafe, consideration should first be given to changing the street block layout. Refer to Section 2.4 and 4.6.

LOCAL TRAFFIC AREA SERVED BY ACCESS STREETS NEIGHBOURHOOD CONNECTOR

INTEGRATOR ARTERIAL SIGNALS

(10-12 m INNER ISLAND DIAMETER) ROUNDABOUTS Smaller roundabouts (inner island

diameter 10-12 m) will be used at most 4-way intersections of Neighbourhood Connectors. Priority control will be suitable for most of the 3-way intersections of the Neighbourhood Connectors.

Intersection Control Guidelines

Page 34

4.4 ‘Primary’ and ‘Intermediate’ Roundabouts on Neighbourhood Connectors

As mentioned in Chapter 2 and as shown in Table 5 and Table 6, the junctions of Neighbourhood Connectors should be controlled with roundabouts in most cases. These are termed ‘primary’ roundabouts under the theoretical model illustrated in Figure 2.

‘Intermediate’ roundabouts may be used to safely manage a 4-way junction in between the ‘primary’ roundabouts and, at the same time, provide a speed control benefit on the Neighbourhood Connector. The

‘intermediate’ roundabouts are also identified in the theoretical model illustrated in Figure 2. However, this frequency of roundabouts may not be desirable if the Neighbourhood Connector is to be used for a bus route.

It is therefore important to liaise with the Department of Transport (Transperth) during subdivision design to avoid objections during the subdivision approval process.

Whenever possible, roundabouts should be used primarily to manage traffic conflicts and only in a secondary capacity to solve speed control problems. The inappropriate use of roundabouts as a ‘cure all’ is not favoured due to the additional land requirements, the additional cost, and in the instance of bus routes, the negative effect on bus passenger comfort.

In document Liveable Neighbourhoods (Page 37-40)