MRWA Supplement to Austroads Guide to Road Design - Part 4

Document No:  D11#308722
 
Revision:  2F
 
Date amended:  11-Dec-2018

Image: orange line.RCN-D13^23151823.GIFThe information below is intended to reflect the preferred practice of Main Roads Western Australia ("Main Roads"). Main Roads reserves the right to update this information at any time without notice. If you have any questions or comments please contact Guillaume Willemsen by e-mail or on (08) 9323 5879.

To the extent permitted by law, Main Roads, its employees, agents, authors and contributors are not liable for any loss resulting from any action taken or reliance made by you on the information herein displayed.

Revision Register

 

Ed/Version Number Clause Number Description of Revision Date

1

All

Guideline Developed. 09-Dec-2011 

1A

4.1

"Priority Junctions" changed to "Unsignalised intersections". 09-Feb-2012

1B

8.2 & 8.2.4

Drawing 9831-5649 amended. 11-Feb-2012
​1C ​4.5.1 ​New clause 4.5.1 "Cross Section Elements" added. ​08-Aug-2012

1D

Header

Contact person changed to Kyle Smith. 16-May-2013

1E

3

Links to Roadtrains at Rural Intersections Drawings added. 06-May-2014

1F

8

"Main Roads Policy - Pedestrians Crossing Slip Lanes at Intersections" added. 07-Jul-2014
​1G​10​"Railway Crossing Control in Western Australia" policy and guideline link amended.​26-Aug-2015
​1H​Header ​Contact person changed to Guillaume Willemsen​25-Jan-2017
​1I​8.2 & 8.2.4​Drawing 9831-5649 amended.​18-Dec-2017
​1J​3​Drawings 201431-0001 and 201431-0002 amended.​18-Apr-2018
​2All​​Updated to supplement Austroads Guide to Road Design (GRD) Part 4 (2017) release.​20-Jul-2018
​2A

5.6.1 & 8.1.1​

​Vehicle Tracking software modelled RAV vehicles added to download file and website links rationalised.​25-Jul-2018
​2B​8.1.2Drawings 200931-0089, 200931-0090 and 200931-0091 amended.​​16-Aug-2018
​2C​3Drawings 201431-0001 and 201431-0002 amended.​​18-Sep-2018
​2D​A.8​Clarification provided for turn treatments on dual carriageways.

Minimum turning volume threshold updated.

​14-Nov-2018
​2E3.1, ​8.2 & 8.2.3​Drawing 9831-5649 amended.​21-Nov-2018
​2F5.6.2​​Clarification provided for car turning radius.​11-Dec-2018

Table of Content


MRWA Supplement to Austroads Guide to Road Design

Part 4 - Intersections and Crossings - General

This Supplement has been developed to be read as a supplement to the Austroads Guide to Road Design (GRD) Part 4: Intersections and Crossings - General (2017), a copy of which can be obtained via the Austroads website.

In Western Australia, state-based information, in this website and elsewhere, takes precedence over Austroads Guides and Standards Australia Standards. National Guides and Standards take precedence over International Guides and Standards, unless specifically stated otherwise.

This Supplement has the same structure as the equivalent Austroads Guide and only additional requirements, clarifications, or practices different from Austroads appear. Where appropriate, this Supplement may also contain additional sections and figures not covered by Austroads, but the numbering sequence found in the Austroads Guide remains. Figures and tables in this Supplement replace those with the same figure or table number in the equivalent Austroads Guide.

 

GENERAL STANDARDS AND APPLICATION

It is important for Road Planners and Designers to be aware of the effects that different types of intersection control may have on delays to traffic (under various traffic demand situations) and the resultant emissions. A range of factors should be taken into consideration when deciding the most appropriate traffic management treatment at any given intersection or crossing. These are outlined in the Austroads Guide to Traffic Management, Part 6, Intersections, Interchanges and Crossings (2007).

Main Roads is aware of the concerns of the community regarding the level of carbon emissions emanating from stationary traffic and the subsequent impact on the environment. Main Roads has undertaken research on a range of traffic scenarios and modelled the emissions emanating from an intersection with roundabout control in comparison with an intersection under traffic signal control.

The findings confirm that, in general, emissions generated at roundabouts are lower than for signalised intersections catering for similar traffic volumes. For larger intersections, the difference becomes more noticeable. That is not to suggest that roundabouts are the most appropriate traffic solution in all situations, but the research should alert Designers to social and environmental benefits that they might not otherwise be aware of when choosing an intersection type.


1. INTRODUCTION

Main Roads has no supplementary comments for this section.

 

2. TYPES OF INTERSECTION

Main Roads has no supplementary comments for this section.

 

3. ROAD DESIGN CONSIDERATIONS FOR INTERSECTIONS

Main Roads has no supplementary comments for this section. In relation to Roadtrains at Rural Intersections Main Roads has developed some typical layouts which can be found in Guideline Drawings 201431-0001 and 201431-0002.

 

3.1 Road Users

For pedestrian kerb ramps at intersection Main Roads considers the absolute maximum grade as 1:10 as shown in Standard Drawing 9831-5649.

 

4. DESIGN PROCESS

4.1 General

Note that the use of aaSIDRA or a similar approved product is also acceptable for determining intersection capacity and layout (i.e. lane configuration). Refer to Austroads Traffic Management Series Part 6: Intersections, Interchanges and Crossings (2007).

The Level of Service (LOS) for intersections is defined in the Transportation Research Board Highway Capacity Manual - Special Report 209 (2000) as the average vehicle delay, which includes both stopped time and geometric delay (slowing down).  This may be calculated as an average for the intersection overall, for each approach, or for each individual movement.

For the design of Main Roads' infrastructure, the target Level of Service for the overall intersection should generally be LOS 'C' with no individual movement less than LOS 'D' for the design year (i.e. 10, 20 years ahead). In the case of signalised intersections where the anticipated cycle length is greater than 120 seconds, or where site constraints limit the number of lanes that can be constructed, the Main Roads Project Manager may accept a lower LOS, provided that the Degree of Saturation (DOS) meets the criteria given below.

For signalised intersections, the degree of saturation (DOS) represents the proportion of available green time capacity taken up for the critical movement(s). For unsignalised intersections, it is the utilisation ratio (volume / capacity or service volume / service rate) for entering movements that must give way. 

The limits of operation for the different types of intersection  shall be:

  • Signalised intersections - the DOS for the critical movement(s) should not exceed 0.9.
  • Roundabouts - the DOS for any movement should not exceed 0.85.
  • Unsignalised intersections - the DOS for any movement should not exceed 0.80.

 

4.5.1 Cross Section Elements

Electrical Assets may be in the vicinity of the road site. Adequate space should be provided for these assets. Refer to Main Roads Roadside Items and Traffic Management Guidelines:


4.5.2 Traffic lanes

For turning laneways, Main Roads has adopted a desirable minimum of 6.0m between kerbs and an absolute minimum of 5.5m.

 

5. DESIGN VEHICLE 

5.2 Design Vehicles

The dimensions and operating characteristics of a Design Vehicle are used to establish specific aspects of intersection layout and road geometry.

Main Roads normally considers these classes of vehicles for design purposes:

  • Car (5.2m)
  • Single Unit Truck/Bus (12.5m)
  • Prime Mover and Semi-Trailer (19.0m)

For the geometric design of intersections, the 19 m Prime Mover and Semi-Trailer right of way vehicle is typically used as the design vehicle for cross section elements and turning paths.

The geometric design should also accommodate Restricted Access Vehicles (RAV) where they are permitted or likely to be encountered.

Refer to the RAV Mapping Tool for RAV location details:

For RAV Networks refer to Table 5.2.2 and Table 5.2.3 for adopted design vehicles.

 

Tandem Drive Network NumberDesign Vehicle
1Austroads Prime Mover and Semi-Trailer (19 m)
2, 3, 4Tandem Drive - Prime Mover, Trailer Combination, Category 2(C) B-Double (27.5 m)
5, 6, 7, 8Tandem Drive - Prime Mover, Trailer Combination, Category 6 (B) B-Triple (36.5 m)
9, 10Tandem Drive - Prime Mover, Trailer Combination, Category 10 (B) B-Double Towing a Converter Dolly Connected to 2 Semi Trailers [Double B-Double] (53.5 m)

Table 5.2.2  Tandem Drives, Networks 1 – 10

Notes:

  1. A Tandem Drive is a motor vehicle incorporating two axles in the drive axle group.

 

Tri Drive Network NumberDesign Vehicle
1, 2, 3Tandem Drive - Prime Mover, Trailer Combination, Category 2(C) B-Double (27.5 m)
4Tandem Drive - Prime Mover, Trailer Combination, Category 6 (B) B-Triple (36.5 m)
5Tandem Drive - Prime Mover, Trailer Combination, Category 10 (B) B-Double Towing a Converter Dolly Connected to 2 Semi Trailers [Double B-Double] (53.5 m)

 Table 5.2.3  Tri Drive, Networks 1 – 5

Notes:

  1. A Tri Drive is a motor vehicle incorporating three axles in the drive axle group.
  2. Due to the only change between Tandem and Tri Drive vehicles being the drive unit, Tandem Drive modelled vehicles are adopted for design, however as these vehicles tend to suffer from understeer an additional allowance of 2 m is made in the minimum turning radii as shown in Table 5.6.2

 

5.3 Checking Vehicle

If a design vehicle chosen for a particular turning movement is the same as the vehicle with the largest swept path permitted on that element of the network then a checking vehicle is not required to be considered.

Checking vehicles may be required where there are known future provisions for larger RAV vehicles than the current design vehicle.

 

5.4 Restricted Access Vehicles

In addition to the RAV network vehicles, on selected intersections (usually associated with heavy load routes) it may be necessary to consider the special requirements of High, Wide Loads.

The Project Manager/Designer should confirm with the Heavy Vehicle Access Plan Manager, the requirements for any over dimensional vehicle needs at the intersection under consideration.

Refer to the Heavy Vehicle section of Main Roads website for details of RAV vehicles and maps of their approved routes.

 

5.6 Design Vehicle Swept Path

5.6.1 General

Main Roads provides on-line turning template drawings for those vehicles that differ from the ones provided by Austroads.  For Austroads turning templates refer to the Austroads Website.

For software modelling of swept paths Main Roads provides custom modelled RAV vehicles for AutoTURN and Vehicle Tracking. Refer to the link below:

RAV custom vehicle templates

Main Roads considers the swept path to be the dynamic envelope traversed by the outer extremities of the vehicle body. Mirrors and other devices fitted to vehicle bodies or wheels are assumed to be accommodated in the required minimum swept path offset.

 

5.6.2 Radius of Turn

Main Roads typically applies a radius larger than the absolute minimum at road intersections to give drivers the opportunity to complete their turn at slightly more than absolute minimum speed.

For cars a minimum turning radius of 6.3m (kerb to kerb) may be used for U turns and driveways.

For RAV vehicles minimum turning radii should match the values below for the equivalent or closest matching vehicle type length.

Vehicle Type

Turning Radius to Outside Front Wheel
(“Kerb to Kerb") ​

Tandem DriveTri Drive
Single Unit (12.5 m)15 mN/A
Prime Mover and Semi-Trailer (19 m)15 mN/A
B-Double (27.5 m)18 m20 m
B-Triple (36.5 m)20 m22 m
Double B-Double (53.5 m)20 m22 m

Table 5.6.2 Minimum Turning Radii

Designers must adopt the following methodology when assessing swept paths:

  • Software parameter “Lock to Lock Time" of 6s must not be altered.
  • Software parameter “Articulation Angle" of 70° (If applicable) must not be altered.
  • Note that Main Roads and software supplied vehicles are set to minimum "Kerb to Kerb" or “Outer Wheel" radii, these must  be altered as per the values in Table 5.6.2.
  • If any of the above parameters are not adopted then agreement should be obtained from the Main Roads Project Manager and the instances must be reflected in the design documentation.

 


5.6.3 Clearances to Swept Paths of Turning Vehicles

Main Roads requires 2 m clearance between all opposed turns.

Where two adjacent turning lanes are required for a turning movement, the left most turning lane must accommodate the largest design vehicle and the other turning lane must accommodate at least a single unit vehicle, with both vehicles assumed to be turning together. If the combined percentage of heavy vehicles (Austroads Classes 3 to 12) in the turning lanes is less than 15%, and the number of heavy vehicles in the right-hand lane is not influenced by a downstream condition then it may be possible to use a car instead of a  single unit vehicle in that lane. This change requires agreement by the Main Roads Project Manager and should be documented in the design report.

 

6. PUBLIC TRANSPORT AT INTERSECTIONS

6.3.4 Bus Stops

The information provided in this chapter should be read in conjunction with the following reference documents:

  • Public Transport Bus Stop Site Layout Guidelines, Public Transport Authority (2016)
  • Guide to the Design of Open Drains, Main Roads Western Australia (2003)
  • Guide to Piped Systems, Main Road Western Australia (2003)
  • Australian Standards 1428.4.1 – Design for Access and Mobility: Tactile Indicators (2009)
  • AASHTO - Roadside Design Guide, (2011, Ch.3)

 

6.3.4.1 Indented Bus Bays

Where practical indented bus bays shall be designed into all new and upgraded road projects that are on bus routes and under Main Roads control, in locations acceptable to both Main Roads and the Public Transport Authority (PTA).


6.3.4.2 General Standard and Application

The primary objective is to produce an indented bus bay design that provides easy and safe entry/exit travel paths, whilst achieving the bus storage capacity required for the particular location.

Bus stops located within through lanes create a disruption to through traffic and may lead to driver frustration, particularly when following a frequently stopping service. As a consequence, risk taking by way of overtaking a stationary bus, may increase. The use of indented bus bays permits a bus to pull clear of through traffic thereby significantly reducing the potential for rear end and side swipe type crashes.

 

6.3.4.3 Design

6.3.4.3a Location

Prior to design, confirmation from PTA is required in relation to the proposed location, size and other requirements for new or relocated indented bus bays. Consultation should also take place with the Local Government Authority (LGA) regarding all aspects of bus shelters that may be located at the indented bus bay site.

It is generally safer to locate indented bus bays well away from intersections, but where this is not practical, it is preferable that the indented bus bay is located on the departure side of the intersection, as shown in Figure 6.3.4a and at the offset shown in Table 6.3.4. In the event that an indented bus bay must be placed on the approach side of the intersection, it shall be in accordance with Figure 6.3.4b and Table 6.3.4.

The location of indented bus bays should be integrated with the street lighting layout to illuminate the area for pedestrians waiting for or exiting and alighting the bus. Desirably, lighting poles should be within 5m to 10m of the pedestrian waiting area.

ROAD
LOCATION
TYPE

PREFERRED
(after intersection)

ALTERNATIVE
(prior to intersection)

 Desirable distance from T.P.

 Minimum distance from T.P.

 Desirable distance from T.P.

 Minimum distance from T.P.

Roads under Main Roads control 

30m

10m

100m

40m

All other roads

Refer to PTA and the relevant Local Government Authority

for location advice
 Table 6.3.4   Indented Bus Bay Proximity to Intersection

 

proximity to departure side of intersection.GIF 
Figure 6.3.4a   Proximity to Departure Side of Intersection
 
 
 

 

proximity to approach side of intersection.GIF 
   Figure 6.3.4b   Proximity to Approach Side of Intersection

 

The indented bus bay should be located so that the Stopping Sight Distance for passing motorists is not compromised. It should be noted that drivers of buses departing from bus bays located on left hand curves have problems sighting vehicles approaching from the rear due to the curvature of the alignment. It is therefore not recommended to locate indented bus bays on left curve alignments unless it can be demonstrated that this problem has been overcome with modified bus bay geometry, refer Figure 6.3.4c.

 

modified geometry - indented bus bay on a left hand curve.GIF 

 

Figure 6.3.4c  Modified Geometry - Indented Bus Bay on a Left Hand Curve
 

Refer to the Main Roads Supplement to Austroads GRD Part 4a: Unsignalised and Signalised Intersections, Section 3.2.2 Table 3.2, for Safe Intersection Sight Distance values.

 


6.3.4.3b Geometric Design

The design of indented bus bays shall generally be in accordance with Figure 6.3.4d. In situations where constraints, (such as services, availability of land) prevent the use of the preferred layout, a reduced length of exit geometry may be permitted (Figures 6.3.4e to 6.3.4h). The Designer should not automatically revert to minimum geometry when restrictions occur, but strive for the maximum practical length taking into account the operating speed of the road and the road hierarchy. Any constraints requiring the bus bay to be less than the standard length should be documented by the Designer. The parallel length of the bus bay shall be determined by the number and type of buses likely to stop simultaneously and should be discussed with Main Roads and PTA.

The minimum width of the indented bus bay shall be 3 metres. This width shall be in addition to the existing/proposed adjacent shoulder width where provisions have been made for on road cycling. Where the demand for on road cycling is low then the 3m indented bus bay width may include the available shoulder width. For information on pavement marking in both cases refer to Section 6.3.4.3e Signs and Pavement Marking.

 

preferred indented bus bay length.GIF 

 

Figure 6.3.4d   Preferred Indented Bus Bay Length

 

 
 

 

 restricted indented bus bay length - 90.0m maximum.GIF

 

Figure 6.3.4e   Restricted Indented Bus Bay Length, 90.0 m Maximum

 

 

 

restricted indented bus bay length - 83.5m maximum.GIF 
 

 

Figure 6.3.4f   Restricted Indented Bus Bay Length, 83.5 m Maximum

 

 

 

restricted indented bus bay length - 75.7m maximum.GIF
 

 

Figure 6.3.4g   Restricted Indented Bus Bay Length, 75.7 m Maximum

 

 

 

restricted indented bus bay length - 67.7m maximum.GIF 

 

 
Figure 6.3.4h   Restricted Indented Bus Bay Length, 67.7 m Maximum
As a general rule indented bus bays should not be combined with auxiliary lanes, or placed closer than 4 seconds of travel time from the end of a lane merge or start of a diverge taper. Refer to Figures 6.3.4i and 6.3.4j.

 

bus bay combined with merge taper.GIF 

 

Figure 6.3.4.i   Bus Bay Combined with Merge Taper

 

 

 

bus bay combined with diverge taper.GIF
Figure 6.3.4.j   Bus Bay Combined with Diverge Taper

 

Indented bus bays on opposing carriageways should be staggered by a minimum distance of 30m. Refer to Figure 6.3.4k.

 

 

 

bus bays on opposing carriageways.GIF 
 

Figure 6.3.4.k   Bus Bays on Opposing Carriageways

 

6.3.4.3c Drainage

Normally, the crossfall within an indented bus bay should be 2% towards the adjacent traffic lane, as shown in Figure 6.3.4l and Figure 6.3.4m. Where the indented bus bay is located on a right curved superelevated road alignment, the indented bus bay crossfall shall be the same as the traffic lanes, as shown in Figure 6.3.4n.

For drainage spread widths applicable to indented bus bays, refer to the Main Roads Guide to the Design of Piped Systems, Table 1.2.

bus bay on a straight alignment.GIF
 
Figure 6.3.4l Bus Bay on a Straight Alignment

 

 

bus bay on a left hand curve.GIF
 

Figure 6.3.4m Bus Bay on a Left Hand Curve

 

bus bay on a right hand curve.GIF
Figure 6.3.4n Bus Bay on a Right Hand Curve

Where possible, drainage gully pits should not be placed within the length of the indented bus bay. Refer to Figure 6.3.4o.

 

bus bay preferred gully location.GIF
 

Figure 6.3.4o   Bus Bay Preferred Gully Location

 

6.3.4.3d Indented Bus Bay Facilities

Paving

A paved hardstand should be provided adjacent to the bus bay (if a footpath/shared path is not required or is not placed against the kerb) for pedestrians entering and alighting from the bus.


Bus Shelters

Where required, bus shelters shall be located in accordance with the following:

  • A minimum 1.9m horizontal clearance from kerb face to bus shelter including any roof overhang.
  • A minimum 1.5m clear footpath width either in front of or behind the shelter for pedestrians walking parallel to the road. Where shelters are placed adjacent to shared paths (pedestrians and cyclists) the minimum path width shall be in accordance with Austroads Guide to Road Design Part 6A: Pedestrian and Cyclist Paths (2007). Consideration should also be given in this situation to accommodate a clearance of 1m from the edge of the bus shelter to the edge of the shared path.
  • The shelter position must not impede the Sight Distance of any driver joining the road from a nearby driveway or side street.


6.3.4.3e Signs and Pavement Marking

Traffic Signs

Signs MR-RPK-6 (L or R) which are equivalent to R5-20 (L or R) in AS 1742.1 are to be used at extremities of the indented bus bay. For stand-alone signs, size "A" should be used. If the "Bus Zone" sign is used in conjunction with other parking series signs, the size will depend on the required sign layout. All other signs advising bus routes and times or associated with other facilities at the bus stop, are not traffic signs and are the responsibility of PTA.


Pavement Marking

Longitudinal yellow continuity lines as shown on Drawing 200331-092 shall be marked across the length of the indented bus bay, including tapers, in line with the kerb face or adjacent edge lines as shown in Figures 6.3.4p and 6.3.4q. Pavement marking shall be long life material in accordance with Main Roads Specification 604.

signs and pavement marking - no cycle lane.GIF
 
Figure 6.3.4p   Signs and Pavement Marking
(No Cycle Lane/Shoulder)

 

signs and pavement marking - including cycle lane.GIF
Figure 6.3.4q   Signs and Pavement Marking
(Including Cycle Lane/Shoulder)

 

7. PROPERTY ACCESS AND MEDIAN OPENINGS

7.2 Property Access 

Refer to Main Roads Driveways guideline, for Main Roads Policy, Application and Approval guidelines and Technical guidelines.

 

8. PEDESTRIAN CROSSINGS

8.1.1 General

For local guidelines and policies refer to the Pedestrian/Cycle Facilities page on the Main Roads website.

 

8.1.2 Types of Crossings

Application of tactile paving

Ground surface tactile indicators are designed to give warning of hazards, and directional information to pedestrians who are blind or have impaired vision.  Refer to AS 1428.4.

Rather than apply such facilities everywhere, it is appropriate to implement tactile devices at selected intersections. These will normally be limited to kerb ramps at frequently used intersection or mid-block crossings in Metropolitan areas. In rural centres tactile paving is less commonly applied and the need to include in a specific project should be confirmed in consultation with the local LGA. 

Section 6.3 of AS 1428.4 shows desirable layout and minimum dimensions. Note that in Western Australia, Type A or B tactile indicators are generally manufactured in 400 mm modules (rather than 300 mm) and thus the dimensions shown in Figure 5 will need to be increased accordingly. Where the direction of pedestrian travel across the roadway is angled from the kerb crossing, Type C indicators should be applied.

Refer to Main Roads Standard Drawings 200931-0089, 200931-0090 and 200931-0091.

 

8.2 Mid-block Crossings on Roads

Reference Table 8.1 “Crossing features and considerations", for the last item in this table refer to drawing 9831-5649 Ramps and Grab Rail Details.

 

8.2.2 General Crossing Treatments

Reference Figure 8.1 Refer to Main Roads drawings 200331-0139 and 200331-0140 rather than Austroads Figure 8.1.

 It is not Main Roads preferred practice to use staggered pedestrian crossings as shown in Figure 8.2.

 

8.2.3 Kerb Ramps for Pedestrians

For pedestrian kerb ramps at intersection Main Roads considers the absolute maximum grade as 1:10 as shown in Standard Drawing 9831-5649.

Reference Figure 8.5 Refer to Main Roads drawing 9831-5649 rather than Austroads Figure 8.5.

 

9. CYCLIST CROSSINGS

Main Roads has no supplementary comments for this section.

10. RAIL CROSSINGS

The following link provides a downloadable version of the Policy and Guidelines relating to Main Roads Document D14#241381. 

"Railway Crossing Control in Western Australia".

 

APPENDIX A   INTERSECTIONS - GENERAL

Location of Electrical Assets should be considered for the site. Further advise for Electrical Assets are given in Main Roads Roadside Items and Traffic Management. Documents may include:

  • Close Circuit Cameras – Vehicle Detector System
  • Design and Installation of Help Phones (Emergency Telephones)
  • Part C: Technical Guidelines (ITS) Document No: 67-08-71
  • Lighting Design Guidelines for Roadway and Public Spaces 
  • Guidelines for Variable Message Sign (VMS) Control

 

A.6 Auxiliary Lane Turn Treatments (Type AU)

Main Roads preferred intersection treatment for most roads is a CHR, AUR or Roundabout.

The AUR turn type works well partially due to the fact that in Western Australia the lane marking differs from other states. The type AUR is a relatively low cost and low maintenance solution to solving high rear-end-major accident rates.

Reference Figures A 6 and A 7, Main Roads does not support the use of lane separation line at AUR intersections. 

A typical type AUR treatment is illustrated in the Figure A 46 below.  Note that the widening (diverge) taper radii shall be designed as per the radii shown therein.

 

Image: typical main roads type aur treatment-3.GIF 

 Figure A 46: Typical Main Roads Type AUR treatment

 

A.7 Channelised Turn Treatments (Type CHR)

Reference Figure A 8, Main Roads does not support the use of the tapered flares at the left turn out of the minor road.  Left turn corners should be based on the swept path of the design vehicle.

A.8 Warrants for BA, AU and CH Turn Treatments

Main Roads does not support the use of the CHR(S) treatment and instead adopts the AUR treatment.

For dual carriageways a CHR treatment should be adopted in place of an AUR treatment.

Due to the high percentage of heavy vehicles on Western Australian roads, Main Roads uses the equation below for warrants for turn treatment in place of Austroads Guide to Road Design (GRD) Part 4 (2017), Figure A 10, and Austroads Guide to Traffic Management, Part 6, Figure 2.26. Note that this equation will match the warrants in Austroads graphs when the %HV equals 7.725%.

 

The following equation is used to determine the turning treatment warranted.

Image: Equation.GIF 

To use the above equation, substitute in values for QM, Qi and %HV

Notes:

  1. QM is calculated based on Austroads GTM Part 6 – 2017, Figure 2.27.
  2. %HV, calculated as the weighted average % heavy vehicles for QM.
  3. Qi is either QR  or  QL.
  4. If Qi is less than 5, only a basic treatment is warranted.
  5. For four lane and six lane single carriageways refer to Austroads Guide to Traffic Management Part 6, (2017), Figure 2.27, for adjustments to QM.

 

For Design Speeds ≥ 100 km/h

If  x < 1, only a BAR / BAL treatment is warranted

If  1 ≤  x < 2.1 , an AUR / AUL(S) treatment is warranted

If  x ≥ 2.1 , a CHR / (AUL or CHL) treatment is warranted

 

For 70 km/h ≤ Design Speeds < 100 km/h

If x < 1.5, only a BAR / BAL treatment is warranted

If 1.5 ≤ x < 3.3, an AUR / AUL(S) treatment is warranted

If  x ≥ 3.3, a CHR / (AUL or CHL) treatment is warranted

 

For Design Speeds < 70 km/h

If x < 2.3, only a BAR / BAL treatment is warranted

If 2.3 ≤ x < 5, an AUR / AUL(S) treatment is warranted

If  x ≥ 5, a CHR / (AUL or CHL) treatment is warranted

 

A spreadsheet using the above equation and conditions can be found here.

 

Example:

Major Road: Two lane single carriageway with a design speed of 80 km/h

Minor Road: Splitter Island included

QT1 = 250 (15%)

QR  = 35 (20%)

QT2 = 300 (15%)

QL  = 155 (12%)

Note above values are peak hour flows with % heavy vehicles.

 Image: Equation.GIF

Right Turn Assessment:

QM = 550

x    = 3.16

Treatment = AUR

 

Left Turn Assessment:

QM = 300

x    = 3.33

Treatment = AUL or CHL

 

A.10.4 Staggered T-Intersection

Rural Staggered T-Intersection Treatments

Reference Figure A 17(a) Main Roads does not support the use of this staggered treatment.

 

A.11.1 Rural Seagull Treatment

Reference Figure A.20, Main Roads does not support the use of continuity lines in the merge area for this intersection type.

 

APPENDIX B   SIGNALISED INTERSECTIONS

B.2.2 Proximity to Other Intersections

Main Roads preferred practice is that intersection proximity is typically determined on the basis of at least five seconds of travel time between an intersection and the start of auxiliary lanes for the next downstream intersection.

When planning locations for new intersections this separation distance should not be solely referred to. Other issues such as road hierarchy, function and operation also need to be considered.

 

B.3.2 Service Road Treatments

Reference Figure B 3 the following treatments are not preferred practices used by Main Roads:

  • In the top left quadrant, the traffic island separating the left turning lane from through lanes is not supported.
  • In the top left quadrant, the egress should be separated by a minimum length of 10 m of parallel kerb.
  • In the bottom right quadrant, the left turn lane consisting of taper only is not supported.
  • In the bottom right quadrant, the egress from the service road blending into the taper for the left turning lane should be separated by a minimum length of 10 m of parallel kerb.

 

B.5 Pedestrian Treatments

B.5.1 Pedestrian crossings

At signalised intersections the width between crosswalk lines should:

  • match the pedestrian ramp width (minimum = 2.5 m); and
  • Where necessary, be wide enough (e.g. = > 5.0 m) to accommodate high pedestrian demands."

 

B.6 Cyclist Facilities

Bicycle lanes on signalised intersection approaches

Main Roads does not support the use of exclusive right turn lanes for bicycles. Right turn head start facilities may be provided at particular locations however access to these facilities are via bicycle lanes located to the left of the leftmost through lane. Bicycles are not allocated exclusive space through the intersection. Refer to Main Roads Standard Drawings 200531-0006 and 200531-0007 for further details. Note that right turn head start storage facilities for bicycles are not used where there is more than one through lane for motor vehicles.

 

Head start and expanded storage areas

Reference Figure B 12 Example (a):

Main Roads position the stop line for motor vehicles 5 m back from the adjacent bicycle stop line (in accordance with Main Roads Standard Drawing 200531-0006), not 2 m as shown in the example.

 

Reference Figure B 12 Example (b):

Main Roads position the stop line for all motor vehicle lanes 5 m back from the bicycle stop line (in accordance with Main Roads Standard Drawing 200531-0006), not with the through / right motor vehicle lanes further forward than the left turn lane as shown in the example.

 

Reference Figure B 12 Example (c):

Main Roads would typically provide a left turn head start storage facility in conjunction with the bicycle through lane.

Main Roads does not support the use of exclusive right turn lanes for bicycles. The right turn head start storage facility would be accessed via the exclusive bicycle lane located to the left of the left most through lane. Refer to Main Roads Standard Drawings 200531-0006 and 200531-0007 for further details. Right turn head start storage facilities for bicycles are not used where there are more than one through lane for motor vehicles.

 

Reference Figure B 12 Example (d):

Main Roads does not support the use of Hook Turn facilities for bicycles. Refer also to Figure B 13. The length of the bicycle head start storage facility shall be 5 m in accordance with Main Roads Standard Drawings 200531-0006 and 200531-0007. Right turn head start storage facilities for bicycles are not used where there is more than one through lane for motor vehicles.

 

Reference Left-turn bypass treatment:

Main Roads does not support the use of left turn bypass facilities (as shown in Figure B 14), due to land constraint issues and conflict with services. Proposals to use such facilities shall be treated on a case by case basis taking into account the aforementioned issues and interaction with other road users such as pedestrians.

 

Reference Bypass of T-intersection:

Main Roads does not support the use of bypass treatments at intersections. Proposals to use such facilities shall be treated on a case by case basis and may result in modification to the treatment shown in Figure B 15.

 

APPENDIX C   CYCLIST CROSSINGS

Main Roads has no supplementary comments for this section

 

APPENDIX D   CRASH TYPES AT UNSIGNALISED INTERSECTIONS

Main Roads has no supplementary comments for this section

 

APPENDIX E   ACCESS SPACING

Main Roads has no supplementary comments for this section

 

APPENDIX F   DERIVATION OF SIGHT DISTANCE REQUIREMENTS AT RAILWAY CROSSINGS

Main Roads has no supplementary comments for this section