Guide to Design and Operation of High Wide Load Corridors

Document No:  D11#318284
Revision:  4F
Date amended:  13-Jul-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 Nick De La Motte by e-mail or on (08) 9323 4448.

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 below or changes to its preferred practice.

Revision Register



Clause Number Description of Revision Date
1 All Guideline Developed 13-May-2002 
2 All Guideline Revised and Approved 20-Feb-2006
2A 4.12 Reference to approved list of removable signpost fixing devices added. 31-May-2006
2B 4.10 Ultimate Limit State Load Factor for Nicolas 16 row trailer amended. 16-Jun-2007
2C 4.12 Relinked to Updated Specification 601. 12-Sep-2007
2D Header Telephone No. of Contact changed. 12-Dec-2007
2E Header Guideline Contact changed. 05-Jun-2009
2F 7 Bridge Loading & Assessment telephone number of Contact changed. 01-Oct-2009
2G All "Drake 22" corrected to "Drake 20" 23-Jan-2010
2H 7 Telephone No. of Heavy Vehicle Notices and Permits Manager changed. 03-Aug-2011
3 Header TRIM No. updated. 12-Jan-2012
4 1, 4.10 & 4.11 Editorial change. 06-Apr-2012
4A 7 Telephone No. of Heavy Vehicle Access Planning Manager changed. 01-Aug-2012
4B 7 Telephone No. and Fax No. of Heavy Vehicle Access Planning Manager & Heavy Vehicle Notices and Permits Manager changed. 30-Nov-2012
4C Header Contact person changed to Kyle Smith. All broken links rectified. 16-May-2013
4D 7 Contacts for High Wide Load Route Planning and Traffic Management removed. 10-Dec-2013
​4E​Header​Contact person changed to Nick De La Motte.​25-Jan-2017
​4F​3.1​Drake 20 length updated.​13-Jul-2017

Table of Content


The following criteria define the design standards needed to satisfy efficient movement of High Wide Loads (HWL). HWL are defined as over-dimensional loads up to 8m high, 8m wide and 24m long with maximum 270t net mass. The design standards for other over-dimensional vehicles can be obtained from Main Roads Heavy Vehicle Operations Branch.

HWL corridors involve the development of suitable transport routes to accommodate large indivisible loads along the designated HWL corridors outlined in Section 3.2 linking key heavy fabrication centres and the Australian Marine Complex (AMC) in the Perth Metropolitan area with mine sites, refineries and other industrial factories that require large machinery and plant. The clearances required for HWL are specified in Section 4.6 Clearances.


Main Roads supports the provision of HWL corridors in WA to improve the efficiency and competitiveness of industry and ultimately the State's economy and also the safety and efficiency of the road network.

All future road works (including pedestrian overpasses) and power line work on designated HWL routes should take into account the HWL requirements.



Three vehicles or approved equivalents have been nominated to carry HWL. The configuration of these vehicles is shown in the diagrams in Appendix B.

  • Drake 20 row 'Two File' at 1.80m axle spacings and 3.70m spread, and overall
    length of 50.84m;
  • Nicolas 22 row 'Two File' at 1.55m axle spacings and 2.99m spread, and overall
    length of 46.50m and;
  • Nicolas 16 row 'Side by Side Four File' at 1.55m axle spacings and 6.22m spread,
    and overall length of 37.26m.

The vehicles have an adjustable platform height above the ground (under loaded conditions) of:

  • 1000mm      standard;
  • 850mm        lowered; and
  • 1350mm      raised.


The proposed High Wide Load trunk routes that link key heavy industry centres and the AMC, in the Perth Metropolitan area are shown in the maps at Appendix A and described as follows. 

  • Corridor 1: Henderson to Kwinana and Singleton (metropolitan region southern boundary).  Along sections of Cockburn Road, Rockingham Road, Patterson Road, Ennis Avenue and Mandurah Road.
  • Corridor 2: Kewdale to Kwinana.  Along sections of Anketell Road, Thomas Road, Tonkin Highway, Roe Highway, Orrong Road and Kewdale Road.
  • Corridor 3: Kewdale to the metropolitan region boundary north and south. Along sections of Abernethy Road, Great Eastern Highway Bypass, Roe Highway, Great Eastern Highway and Great Northern Highway.

Network planning for the movement of HWL outside of the Metropolitan area is being developed by the Department for Planning and Infrastructure. When undertaking future road works (including pedestrian overpasses) and power line work on designated HWL routes outside of the Metropolitan area consideration should be given to the requirements for HWL. This should be done in consultation with Main Roads, Road Network Services Directorate (see Section 7.0 for contact details).



These criteria are to be applied to new roadwork and power line modifications on HWL routes.  Existing infrastructure that can accommodate the absolute minimum clearance requirements (refer to Section 4.6) without alteration need not be modified to meet the design criteria.  Any alteration should be based on the desirable minimum clearance requirements as per Section 4.6 Clearances. 

Contact persons and their details are listed in Section 7.0 Contacts.


The turning templates for the three trailers described in Section 3.1 have been developed and appear in Appendix B.

Designers should be aware that only some of the commercially available turning templates software can accurately model these HWL turning templates. These three vehicle types have been already added to some commercially available turning templates software. Designers should check any software generated templates by overlaying them on the templates in Appendix B.

The turning templates for other trailer configurations have also been developed by the trailer manufacturers.  However, to date these templates only cover the circular section of the turning paths. Copies of some of these are available from Kingston Industries (WA) Pty Ltd. To be able to model the movement of the trailer and its load through an intersection, the start and end tapered sections of the turning templates need to be developed.

The following procedure is recommended when developing new turning templates: 

  • Establish an intersection using sandbags in a suitable location such as a transport contractor's premises to test the vehicles' turning capacity;
  • Mark out the paths followed by the trailer and prime mover as they approach, move through and depart from the curve;
  • Survey and create a digital drawing of the path followed;
  • Create a computerised model of the prime mover(s)' and trailer's paths using a suitable turning template package and calibrate this to ensure correlation with the field trial results;
  • Develop a model of the swept path of the load, based on the calibrated model of the turning movement of the prime mover(s) and trailer; and
  • Model the turning movements through the intersections along the route and identify any improvements necessary. It should be noted that the swept path of the prime mover(s) and trailer will differ from that of the load overhang and both need to be modelled and assessed.



Before applying the relevant design criteria, a detailed route assessment must be carried out to identify any possible risks or dangers for the movement of high wide loads.

An effective route assessment should promote the following principles:

  • Achieving HWL clearance envelope requirements;
  • Maintaining integrity of bridges and other structures;
  • Ensure safe and efficient transport; and
  • Appropriate traffic management.

A route assessment shall be carried out with appropriate traffic management measures to identify any modification work required. Delays to the other road users during undertaking these investigations shall be kept to minimum.

It is recommended that before finalising the HWL route, replicated vehicles (full size unladen vehicles) should be driven along the selected routes, with their overhang and pivot point paths manually plotted. This will enable identification of roadside furniture, vegetation and other obstacles that may be affected by the movement of such vehicles.

It is envisaged that as HWL movements become more frequent, the impact of HWL movements on other road users will become more problematic. The impacts of HWL on the operation of a road should be assessed, based on the available traffic data.


When determining appropriate road widths all roads which form part of a HWL route need to be able to accommodate the physical dimensions of the nominated HWL vehicle. The road widths specified in Figures 1 and 2 are total widths required to accommodate the movement of HWL on the nominated trailer platforms.

For stability reasons a HWL should remain on the sealed portion of the road cross section.  The availability of full width seal on shoulders will therefore be a consideration.


Figure 1: Full Width Sealed, Kerbed and Unkerbed Single Carriageway Roads



Figure 2: Full Width Sealed, Dual Carriageway Roads, Kerbed and Unkerbed Both Sides

The carriageway widths in Figures 1 and 2 have been derived to facilitate the passage of HWL, and are based on straight sections of road. At sharp curves the required width should be determined using vehicle swept paths.  The minimum seal width to accommodate the nominated HWL trailer platforms is 7.22 metres.

For two lane single carriageway roads consideration can be given to extending the road seal width to allow other traffic to flow in the opposite direction. The required road seal width is shown in Figure 1.

For dual carriageway roads vehicles travelling in the same direction as the HWL will need to queue behind until there is an opportunity to overtake the HWL through the provision of additional seal widening or the HWL is moved into a holding bay. 

HWL holding bays can be installed at suitable locations where the HWL can pull-off the road, allowing vehicles queued behind a HWL to pass. On more heavily trafficked roads, the provision of bays alone may result in unacceptable bay spacing.  In such cases, widening of the road to allow other road users to pass the slow moving HWL may be considered. A copy of a typical holding bay drawing is attached in Appendix D.

Freeway "on-ramps" and "off-ramps" should be treated the same way as a dual carriageway road kerbed both sides.  Required sealed width is as shown in Figure 2.

In urban or "built up" areas, site specific issues such as non removable roadside furniture vegetation etc must be determined and planned for. 


The requirements for the median and turning islands are based on allowance for the load overhang.  In all instances traffic islands and medians should be retained, albeit the form may vary from the current standards.

    • Absolute maximum height for trafficable median/central island, with semi-mountable or mountable kerb and reinforced concrete infill shall be 150mm.
    • Where the central island/median is non-trafficable and has obstacles or non-removable road furniture, the absolute minimum median width shall be determined by allowing 0.5m clearance (on both directions of travel) to the obstacles or non-removable road furniture.  If the intersection has a right turn pocket and providing that the HWL vehicles are not turning then the median width will be controlled by other design requirements as specified in Section 4.9 Road and Traffic Engineering Standards.

Safety of other traffic including pedestrians and cyclists should be considered when using mountable kerbs.



The desirable minimum clearance envelope requirements for HWL corridors is 10 metres, high by 10 metres, wide.  As shown in Figure 3 the following HWL clearances shall be provided

  • 1.0m  -  absolute maximum height of non-removable roadside furniture, relative to road surface, 
                 where load overhangs medians, islands and verges;
  • 1.0m  -  desirable minimum lateral clearance between laden vehicle and non-removable roadside furniture 
                 which exceeds 1.0m height; and
  • 0.5m  -  absolute minimum lateral clearance between laden vehicle and non-removable roadside furniture 
                 which exceeds 1.0m height; and





Figure 3: Clearances Envelope Requirements


Where roads are to be grade separated the HWL Corridor route should desirably pass over cross roads to reduce clearance requirements and costs.

Where the HWL corridor route passes under the crossroad and the crossroad links to the HWL corridor with an interchange, a diamond shape interchange parallel to the corridor should be installed to minimise clearance requirements at the interchange.  If there is no connection between the HWL route and the crossroad or if there is an existing non-diamond interchange, an alternative route (a detour only for the use of HWL or cross over to opposite carriageway) should be considered with the development of an appropriate clearance, based on suitable treatment satisfying the minimum design requirements as specified in Section 4.6 Clearances.


The nominated HWL vehicles can only accommodate certain level differences over the length of the trailer. This difference is trailer specific ranging from 460 mm for the Drake 20 trailer to 500 mm for the Nicholas trailers. As the Drake 20 trailer can only accommodate a 460 mm level difference and is longer than the other trailers it is to be adopted as the basis of design.

The level difference characteristics of the HWL trailers is to be considered were there are changes in longitudinal road gradients as shown in Figure 4, as well as level differences created by road crossfall or superelevation.


Figure 4: Level Difference Over Platform

The Road & Traffic Engineering Branch has developed software that runs in conjunction with MX to check the level difference. This is available for all MX users and should be used to check the level difference criteria on all HWL designs.

The following grades and superelevation are recommended. These requirements should not override the other traffic engineering standards specified in Section 4.9.

Maximum grade 6%
Maximum superelevation on main carriageway 6%

For loop ramps, up to 7% maximum superelevation can be used as long it satisfies the level difference requirement.


The design must comply with all other Main Roads and Austroads Road Design and Traffic Engineering Standards (which will be applicable for general traffic).



All structures shall be designed to accommodate nominated axle loads for the high/wide loads route trailers or approved equivalent listed below:

  • Drake 20 row 'Two File' at 1.80m axle spacings and 3.70m spread with 14.5t per row;
  • Drake 20 row 'Two File' at 1.80m axle spacings and 3.70m spread with 18.0t per row for Pilbara only;
  • Nicolas 22 row 'Two File' at 1.55m axle spacings and 2.99m spread with 13.5t per row; and
  • Nicolas 16 row 'Side by Side Four File' at 1.55m axle spacings and 6.22m spread with 20.5t per row.

These various row loadings will allow the required 200t net load for each vehicle and 270t net load for the Drake vehicle for bridges in Pilbara region, in accordance with the requirements for the high/wide loads corridor.

Details of these vehicles are included in Appendix B. The steer load is 6t and the drive is 18t for each block truck required to move the trailers, as detailed in the attached diagrams.

All vehicles shall be treated in the same manner as the Heavy Load Platform design vehicles (Refer Australian Standards AS5100; Reference 1500.2 Bridge design - Design loads, Clause 6.3). However, given strict control of movement the location of plus and minus sign.GIF 0.5m of any position can be used. 

For dual carriageway bridges, all vehicles may be removed from the other carriageway if there is a bridge strength requirement.


The High Wide Load vehicles may carry loads of up to 270t.

All new pavements shall be designed in accordance with the Main Roads Standard Design Brief; Sections 204.3 Pavements and 204.4 Surfacings.


The above represent the design criteria that should be used to maintain traffic control and road safety.  It must be recognised that there may be situations where alternative methods of traffic control are necessary.  The options detailed below need to be considered only as an exception to the design principles adopted above.  Permanency of the route is an essential requirement.

  • Where traffic signals or regulatory signs such as STOP and KEEP LEFT cannot be relocated to a permanent position clear of the laden vehicle, detachable posts may be located in sleeves cast into the traffic island to permit easy removal. Before incorporating this arrangement into the design, ongoing operational costs should be assessed against costs of other available options. These signal/signposts need to be either bolted or padlocked to the footing sleeve. Refer to Main Roads Standard Specification 601 - Signs, for a list of approved removable signpost fixing devices;
  • Where HWL turning movements are constrained at intersections median cross overs (with removable barriers) and traffic contra flow arrangements may be considered to avoid significant impact on major intersections; and
  • Where HWL access is constrained in clearly identified areas, crossing over to the opposite carriageway of a dual carriageway through the median (with removable barriers).

To accommodate crossing over to the opposite carriageway, flush medians can be provided by using mountable or any other low profile kerb. A removable barrier such as bollards may be required along the centre of the flush median (parallel to the carriageway) to prevent U-turn movements by other vehicles.  Any removable barrier should not be hazardous to other motorists.

The circumstances for the above shall be clearly identified in the development of the concept design plans for the route and necessary approvals shall be obtained from the relevant Traffic & Safety Services Manager.



Overhead Distribution power lines up to 33kV crossing HWL routes should be relocated or placed underground.

Overhead Transmission power lines 66kV to 330kV crossing HWL routes should be relocated or raised to provide the required clearance to move HWL while the systems are energised. The Western Power safe approach unescorted clearance for Transmission lines are shown in Appendix E and will determine the raised height of Transmission lines or their relocation.

When determining clearances the desirable minimum clearance envelope is 10.0m wide x 10.0 m high plus the electrical clearance requirements.

The Western Power contact details can be found in Section 7.0 Contacts.


Any existing manholes or other service structures within the swept path of the High Wide Load should be checked for structural adequacy.



HWL movements have potential to impact negatively on traffic flow and the safety of other road users.  It is therefore necessary to consider and plan for the management of these impacts.  The overall efficiency and safe operation of the road network must be managed by balancing of:

  • Availability of holding bays, seal widenings and other passing opportunities,
  • Number of HWL movements and temporal allocation (time of day/week) for HWL movements and
  • Adequate Traffic Management Plans prepared and implemented that manage impacts and minimise delays to other traffic.

However, it may not always be possible to achieve the desirable holding bay and seal widenings due to constraints such as land availability, environmental issues or limited funds.

The interaction between HWL and other traffic will typically occur in two distinctly different situations:

  • single carriageways with two-way traffic flow and
  • dual carriageways where the traffic flow on any one carriage way is in one direction.


The impact of HWL movements on other road users can be measured in terms of either delay or maximum queue length (number of vehicles). Indicative Level Of Service (LOS) is as follows:

  • Delay to other road users - maximum 5 minutes additional travel time (especially relevant on higher trafficked roads)
  • Maximum queue length - 50 vehicles (more relevant on lower trafficked roads)

The practicality of achieving these indicative LOS targets depends on consideration of factors such as class/importance of the road, traffic volume (daily and peak hour), general traffic speed, speed of HWL, number and duration of HWL movements and funding available for infrastructure.


On single carriageway roads the preferred traffic management measures include:

  • the provision of sufficient / additional seal width to allow traffic travelling in the direction opposite to HWL to pass the HWL and
  • holding bays at regular intervals to allow following traffic to pass the HWL without experiencing excessive delay.

However, if this not achievable it may be necessary to prohibit traffic flows in the direction opposite to the HWL movement. If the road network allows, it may be possible to establish diversions for general traffic to alternative routes to minimise delays and disruption. However, this may not be possible for the diversion of permit vehicles using the designated HWL route.


On dual carriageway roads the preferred traffic management measures include:

  • the provision of sufficient / additional seal width to allow traffic travelling in the same direction as HWL to continuously pass the HWL movement and / or
  • holding bays at regular intervals to allow following traffic to pass the HWL without experiencing excessive delay.

However, if this is not achievable the impact on other road users can be managed via the provision of holding bays at appropriate intervals.

Heavy haulage operators must develop a traffic management plan when undertaking the movement of a high wide load.  Its scope will depend on the size of the load and the route taken. A major part of the plan will be steps taken to minimise delay and annoyance to other road users. This includes arranging for other traffic to bypass the load, safety considerations and the direct problems of getting the convoy itself along the route.

To minimise traffic safety and efficiency impacts HWL shall not be transported during periods of peak traffic or at night.

A public notice will normally be required in the local and state media advising of the time and route for the HWL, with a minimum of 72 hours notice to road users. A detailed communication plan may be required for moving larger loads which may cause significant delays to the other road users.

The basic Guideline for Preparation of a Traffic Management Plan has been developed by Main Roads, which will assist the operator to develop an appropriate plan, and act as a checklist to allow Main Roads to check its appropriateness. This guideline will be updated following feedback received from future High Wide Load moves. The Guideline for preparation of a Traffic Management Plan and a sample copy of a Traffic Management Plan, which has been used in the past, can be found in Appendix C.

The assistance of Police and Pilots is mandatory for the movement of HWL.






High Wide Load Design Standards Heavy Vehicle Access Planning Manager

9475 8451

9475 8455

Bridge Loading and Assessment Engineer Bridge Loading

9323 4111

9323 4336

Pavement Engineering Pavement & Surfacings Manager

9350 1401

9451 1400

High Wide Load Route Operations Heavy Vehicle Notices and Permits Manager

138 HVO(486)

9475 8455

Western Power Network Engineer

9326 6467

9326 6400






High Wide Load Corridors metropolitan

Map 1

High Wide Load Corridors 1


High Wide Load Proposed Corridor 2


High Wide Load proposed Corridor 3




Copy of vehicle diagrams and draft turning templates are as follows:


Drake 20 Row '2-File' Drawing being developed Figure 1
Nicolas 22 Row '2-File' 200131-075 Figure 2
Nicolas 16 Row '4-File'


Figure 3


Electronic copies of these templates (in AutoCAD format) can be obtained from Con Magriplis of Main Roads, Road and Traffic Engineering Branch.



Guideline for Preparation of a Traffic Management Plan

A copy of Sample Traffic Management Plan



A Typical Holding Bay Drawing