MRWA Supplement to Austroads Guide to Road Design - Part 4

Document No:  D11#308722
 
Revision:  1H
 
Date amended:  25-Jan-2017

Image: orange line.RCN-D13^23151823.GIF 

 

The 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

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 (2009), a copy of which can be purchased 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.


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 consider four general classes of vehicles for design purposes:
    • B-Double (27.5m)
    • Semi-trailer (19.0m);
    • Single Unit Truck/Bus (12.5m); and
    • Car (5.0m)

 

For the geometric design of intersections, the 19 metre Semi-trailer is typically used as the design vehicle for cross section elements and turning paths and the Car is used as the design vehicle for horizontal and vertical geometry. The geometric design should also be checked for other design vehicles (such as B-Doubles or Road Trains) where they are likely to be permitted or encountered.

 

In rural areas (as a minimum) intersections on major roads and highways should be designed to cater for a 19m Semi-trailer or a 27.5m B-Double as necessary.

 

The geometric design should be confirmed for the largest design vehicle expected to use the road. On selected urban intersections (usually associated with heavy load routes) it may also be necessary to consider the special requirements of High, Wide Loads. Refer to the Design Guideline for 'High Wide Loads' for information on these vehicles, route descriptions and route sketches.

 

Further information for Oversize and High Wide Loads can be obtained from the Main Roads Heavy Vehicle Operations Website Heavy Vehicles - Policy and Guidelines. 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.

 


5.6 Design Vehicle Swept Path

 

5.6.1 General

 

To establish the "Swept Path Envelope" for the required design vehicle, turning templates have been developed for the most commonly used vehicles listed in Chapter 5.2 plus several other combinations. The turning templates may be downloaded and printed onto transparent film for use when designing on a hard copy. There are computer programs available (V-Path, AutoTURN, AutoTRACK etc.) for use when designing on a computer. The use of computer programs that generate the swept path templates are a more accurate and flexible method (Main Roads preferred method) than the hard copy method. The Designer should use the vehicle configuration shown on the Main Roads turning templates when using these programs.

 

Kerbs shall typically be located 500mm clear of the truck swept path (including vehicle body overhang). Truck stability should be considered for turning movements at intersections and crossfall with a uniform rate of change should be provided. The minimum design clearance between vehicle swept paths running parallel to each other either on a straight alignment or double left or right turning movement shall be 1m.

 

 
5.6.2 Radius of Turn

 

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

 

Vehicle Type

Turning Radius to outside front wheel

 Single Unit 12.5m 

15+m

 Semi trailer 19.0m 

15+m

 B-Double 27.5m 

18m

 Double Road Train 36.5m 

20m

 Triple Road Train 53.8m 

20m

 

Table 5.6.2 Preferred Minimum Turning Radii

 


5.6.3 Clearances to Swept Paths of Turning Vehicles

 

Main Roads requires 2m 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.


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 (2010)
    • 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, (2002, 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.

Refer to PTA's 'Public Transport Bus Stop Site Layout Policy',  Austroads Road Design Part 4A: Unsignalised and Signalised Intersections, Chapter 3 - Sight Distance, and the Main Roads Supplement to Austroads GRD Part 4A.


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

Local Guidelines

    • Austroads Guide to Road Design Part 6A: Pedestrians and Cyclist Paths (2009), Chapter 8.
    • Main Roads Design Guidelines for Channelisation Pavement Markings and Regulatory Signs
    • Main Roads Pedestrian Level of Service Guidelines
    • Main Roads Cycling Level of Service Guidelines
    • Bicycle Directional Signage
    • Main Roads Disability Access and Inclusion Plan 2007-2011
    • Local Government Pedestrian and Cycling plans
    • Traffic Engineering Technical Standards: Volume 2 - Parts 1 & 2


Main Roads Policies


Department of Transport and Bikewest Policies

    • Metropolitan Transport Strategy
    • Bike Ahead
    • Perth Bicycle Network Plan
    • Perth Walking - The Metropolitan Region Pedestrian Strategy.

 


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 400mm modules (rather than 300mm) 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.


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 200331-139 & 200331-140 rather than Austroads Figure 8.1.

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


8.2.4 Kerb Ramps for Pedestrians

Reference Figure 8.6 Refer to Main Roads drawing 9831-5649 rather than Austroads Figure 8.6.


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"

For geometric guidelines refer to Austroads GRD Part 4: Intersections and Crossings - General (2009).