Good morning everybody. Thank you for the opportunity to speak to you this morning
My name is Derrick Hitchins and I am the National Sector Leader Traffic and Transport Planning for SMEC, currently based in Brisbane
New vehicle designs offer significant advantages to commercial freight operators in terms of volume and payload.
For this reason it is inevitable that the industry will continue to call for a change to the rules and regulations that govern them.
With the advent of larger and heavier vehicles, the pressure is mounting on the various state road authorities and enforcement agencies to continue to modify their standards and guidelines with respect to the operation of those vehicles and the impacts they are having on : driver behaviour, associated minimum safety standards and the condition of our roads.
As a way forward, it is imperative that we as traffic engineers become more familiar with the requirements of this ever-changing heavy vehicle fleet and learn to assist in accommodating these larger vehicles on our busier urban and regional road networks.
The outline of my presentation to you this morning is as follows:
We will explore the question of … REFER TO SLIDE
High productivity vehicles such as conventional ‘road trains’ are now commonplace in a number of countries including Argentina, Mexico, the United States, and Canada.
Australia, however, has the largest and heaviest road-legal vehicles in the world, with some configurations topping out at close to 200 tonnes in the case of vehicles being used on the mines in WA.
The cost-effectiveness of these larger vehicles has played a significant part in the economic development of some of the most remote areas in Australia with some communities being almost totally reliant on these vehicles for their economic sustainability.
A number of government publications provide guidelines for classifying what a multi-combination vehicle may look like,
but in essence there are really only three major categories to contend with:
19m-25m – mainly B-doubles or derivatives thereof Type 1 road trains up to 36.5m max or derivatives thereof Type 2 road trains up to 53.5m max or derivatives thereof
As you can see from the slide, the B-double (19m) falls into the general access vehicle class and as such does not require a notice or permit to operate on our roads
Now once you move away from the classic B-double things start to get very interesting.
You would think that a Road Train might refer to the use of a Prime Mover with two or three trailers much like a train, but obviously not.
Road trains also include a number of closely coupled A class and B type vehicles such as the B-triple and AB-triple as illustrated above.
Using the individual units that comprise those combinations, a number of other configurations are also possible within the vehicle class.
For those of you that may be unfamiliar with the terminology, the A’s and the B’s refer to the type of couplings which when combined with the number of trailers result in the vehicle type nomenclature referred to above..
Looking at the Type 2 Road Trains by comparison, it would appear as if every combination that could ever have been thought of has been captured in this all-encompassing Type 2 vehicle class, as long as in combination the overall length remains below the magical 53.5m !
And just to complicate matters even further, we find the good old 12.5m rigid truck hidden away within the Type 2 road train combination too.
So what does all of this mean in terms of safety. What does this all mean in terms of vehicle performance. And what does this all mean in terms of road design.
It is at this point as traffic engineers that we have to start asking the question: “Why has this been allowed to occur at all, and at what point have we gone too far ? ”
To illustrate this point I thought it might be useful to look at some actual examples of vehicles that have been photographed as they travel along our asphalted roads.
REFER TO SLIDE
2 – B Double 3 - Road Train Type 2 – Prime Mover towing THREE semi-trailers by drawbars 4 - Iron Ore Road Train in Western Australia with FOUR semi-trailers by drawbars 5 – 6 – Road train on Pinterest 7 – British Petroleum ?? – Not even sure how to count ??
So lets have a look at why there is such a push to have longer and bigger trucks
In essence, it comes down to there key attributes:
an increase in payload, an increase in volume and a reduced running cost.
The graph above illustrates this point.
Heavy Vehicle National Law governs road access arrangements.
This law governs the use ……
All vehicles above 19m fall into the Restricted Access Vehicle Category.
This means that some B-doubles trigger the need for a notice or permit and then of course all other vehicles and combinations above that length do too.
Examples of the types of vehicles that fall within the Type 2 vehicles class include …
REFER TO SLIDE
PBS is an alternative regulatory scheme for heavy vehicles that was developed throughout the 2000s
The aim was to allow for a more widespread adoption of higher productivity vehicles.
The PBS was initially trialed by jurisdictions and subsequently formally adopted by the NTC in a regulatory sense in 2011.
The standard seeks to achieve:
a more sustainable transport system through improved road vehicle regulations a more flexible road transport regulatory environment that allows for greater innovation in vehicle design
The levels of road access range from general access (Level 1) through to (Level 4) which is more akin to the remote areas within Australia with low traffic volumes
The table provides a comparison between road classification levels and equivalent maximum vehicle lengths.
Because of the strong influence of length on gazetting existing networks for PBS, the NTC decided to split three of the four PBS levels into two sub-levels
This created ‘Class A’ and ‘Class B’ within PBS Level 2, 3 and 4.
As you can see, there is a direct translation between the existing Restricted Vehicle Access classification and roads classified under PBS.
The National Heavy Vehicle Regulator (NHVR) was established in 2013 as Australia’s independent regulator for all vehicles over 4.5 tonnes.
The NHVR manages the access of heavy vehicles to ensure a safe, efficient and sustainable road network for industry, and administers the PBS scheme.
The NHVR is not a road owner, but rather coordinates a range of access applications from start to finish, liaising directly with road managers (both state and territory road authorities and local government) to manage applications and issue permits.
To begin with, REFER TO SLIDE, etc.
PBS Class B categories provide for slightly longer vehicles than the current general access levels allow. This is usually in the order of 6 to 7 m more in overall length.
As such, the increased vehicle length will potentially affect road design aspects such as :
Longer storage lane lengths at intersections; Longer signal timing for left or right turns at intersections; Increased overtaking provisions on rural roads; Increased enforcement bays and rest area sizes; More stacking distance at railway level crossings; Larger radius swept paths and median openings Greater impact on last mile constraints within urban areas or near freight terminals for example.
It is a common misconception that larger and heavier vehicles are less safe.
As a result of a rigorous accreditation process, PBS vehicles are subject to sixteen stringent safety-related and four infrastructure-related performance standards. These criteria are known to result in a higher level of safety than the average non-PBS vehicle of earlier years.
In the case of Non PBS vehicles, research conducted by Austroads has produced some interesting results. Based on crash data compiled by National Transport Insurance since 2005, Austroads found that with the larger size vehicles there is actually a greater level of safety.
Reasons include: Better driver education Safer performance of larger vehicles increased levels of enforcement Greater participation in the Intelligent Access Program (IAP)
So why all the fuss ?
Well, we know that longer heavier vehicles will result in ….. REFER TO SLIDE, etc.
On the flipside however, this will result in an increased impact on …. REFER TO SLIDE, etc.
Increased vehicle lengths in most cases leads to an increased minimum low speed turing radii.
REFER TO SLIDE
Mitigation includes: Pavement widening Additional line marking / painted islands Roadside furniture set back
The aim of this performance standard is to limit the damage caused to pavements by the vertical load of each vehicle axle on the road pavement and bridge structure.
If vehicles have
tri-axle groups, are fitted with certified road friendly suspension, and are using an authorized HML route,
then higher mass entitlements could apply.
REFER TO SLIDE
Another important aspect to take into account when comparing single versus multi-tyre axle assemblies is the potential for increased pavement damage caused by unequal load distribution.
As illustrated in the slide, uneven wheel loadings increased vehicle point loads and with it the load that damages the road pavement most.
REFER TO SLIDE
Bridge capacity is perceived as being one the most critical issues to be addressed.
However, from a structural perspective, heavier payloads do not necessarily relate to greater relative bridge impacts.
This is because in some instances the longer vehicle types are able to spread their axle loads more evenly across the structure, or even bridge a short span length.
REFER TO SLIDE
This measure considers the vehicle’s ability to remain within the available traffic lane width along a straight road.
Vehicle performance is influenced by variations in the road surface due to cross-fall, unevenness and localised failures on occasion.
Mitigation: increase the available lane width or construct a surfaced shoulder
Consistent with the importance attached to these measures, the findings of a recent study undertaken by SMEC confirms that the motoring public have a similar perception of what is important from a road safety perspective.
Key findings include the significance being attached to concerns such as
Road width / lane width Road surface condition,
versus a slightly larger group of lesser but no less important safety concerns.
As a final outcome to the issue of larger and heavier trucks on our roads I wish to draw your attention to some of the practical implications of not sticking to the original plan. Road pavement failure is one of the most obvious symptoms that result when things go wrong.
The main distress modes, especially from the point-of-view of traffic loadings are:
fatigue cracking which occurs mainly on the surface of relatively weak or thin pavement structures;
primary rutting which occurs mostly on thick bituminous asphalt pavements and is confined to the upper pavement layers;
secondary rutting which occurs mainly on relatively weak / thin pavements and is primary linked to severe subbase failure, i.e. all pavement layers are affected
ravelling being the loss of stone in the surface of the pavement usually caused by a great number of horizontal shear loading cycles, i.e. heavy turning movements
potholes resulting either from localised pavement failures or from water ingress (often through open cracks)
roughness also referred to as unevenness of the pavement due to many factors including rutting, cracking, potholes and uneven settlement.
So finally, in conclusion, how should we as traffic engineers respond ? In my opinion, it is recognised that ….
REFER TO SLIDE.
Size does matter - but when is big too big?
SIZE DOES MATTER –
BUT WHEN IS BIG TOO BIG?
Derrick Hitchins, SMEC Australia
2016 AITPM National Conference, Sydney, July 2016
• New vehicle designs offer significant advantages to
commercial freight operators in terms of volume and
• For this reason it is inevitable that the industry will continue
to call for a change to the rules and regulations that govern
• In response, state road authorities and enforcement
agencies have to continue to modify their standards and
guidelines with respect to the operation of those vehicles
• It is therefore imperative that we as traffic engineers
become more familiar with the needs of this ever-changing
heavy vehicle fleet.
A. How big is Big ?
B. Road Access Arrangements
C. Treatment of high-productivity vehicles in Queensland
D. Understanding the impact of these larger vehicles on our
E. How should traffic engineers and planners respond
General Access Vehicles
A. How big is Big ?
• B-double (19m max)
• Do not require a notice or permit to operate on the road
• Have general access to the road network unless the road is
Prime mover towing two semi-trailers connected by a drawbar
Type 1 Road Trains (36.5m max)
Type 2 Road Trains (53.5m max)
Prime mover towing three semitrailers connected by drawbars
Rigid truck towing two semitrailers connected by a drawbar
Productivity Benefits Quantified
8Source: Moving Freight: An update on road network freight access
Heavy Vehicle National Law (Commonwealth of Australia)
• Governs the use of B-doubles in stated areas, on stated
routes, during stated hours of stated days and under stated
• The NHVR liaises directly with road managers to manage
applications and issue permits.
For General Access Vehicles (i.e. < 19m)
• Road managers provide pre-approved consent for a range of
approved heavy vehicle routes
• In turn, Austroads (2009) guidelines for Arterial Roads
requires designers to
– Design for 19m vehicles and check for 25m e.g. B-double
B. Road Access Arrangements
B-double (23m-25m-27.5m max)
NHVR Class 2 Heavy Vehicles - Notice or permits must issued by
National Heavy Vehicle Regulator (NHVR).
A-double (36.5m max)
B-triple (53.5m max)
Restricted Access Vehicles
• PBS is an alternative regulatory scheme for heavy vehicles
that was developed throughout the 2000s in order to meet
the demands of the growing road freight task and allow more
widespread adoption of higher productivity vehicles.
• It was initially trialed by jurisdictions and subsequently
formally adopted by the National Transport Commission (NTC)
in a regulatory sense in 2011.
• The standard seeks to achieve:
– a more sustainable transport system through improved road
– a more flexible road transport regulatory environment that
allows for greater innovation in vehicle design
Performance Based Standard
C. Treatment of high-productivity
vehicles in Queensland
• Department of Transport and Main Roads publishes a set of maps
via their website (same for all other States)
• Direct translation between the existing Restricted Vehicle Access
conditions and roads classified under PBS.
• To begin with, the applicant needs to consult with the
relevant road authorities to discuss the likelihood of being
granted road network access
• Only accredited PBS assessors can submit PBS Design
applications to the NHVR. Includes investigation of road
network access to design development stage.
• Onus is on the applicant to prove suitability of the proposed
vehicle design as well as the associated vehicle mass, bridge
loadings and the level of PBS network compliance.
• Funding of infrastructure improvements by PBS applicant is
considered on a case by case basis.
• Only after PBS vehicle approval can applicant apply for a
permit with the NHVR.
PBS Road Access Application
PBS Class B categories provide for longer than current general
access, B-double, Type 1 and Type 2 road train combinations.
• Longer storage lane lengths at intersections;
• Longer signal timing for left or right turns at intersections;
• Increased overtaking provisions on rural roads;
• Increased enforcement bays and rest area sizes;
• More stacking distance at railway level crossings;
• Larger radius swept paths and median openings
• Greater impact on last mile constraints.
PBS Class B network
• The B double is currently Australia’s safest and most efficient
mainstream heavy freight vehicle.
• Reasons include
– Better driver education
– safer performance of larger vehicles
– increased levels of enforcement
– Greater participation in the Intelligent Access Program (IAP)
D. Understanding the impact of these
larger vehicles on our roads
• Less heavy vehicles on
• More efficient movement
• Increased payload
capacities, especially for
minerals and grain
• Intersection geometry
• Pavement loading
• Bridge loading
• Road width requirements
• Actual road wear
So why all the fuss ?
• Low speed swept path impact on existing intersections most
• Mitigation includes:
– Pavement widening
– Additional line marking / painted islands
– Roadside furniture set back
Pavement loading (1/2)
Maximum mass (tonnes)
permitted under GML
Maximum mass (tonnes)
permitted under HML
Single drive axles on buses 9.0 t 10.0 t
Six-tyred tandem axle groups 13.0 t 14.0 t
Tandem axle group 16.5 t 17.0 t
Tri-axle group 20.0 t 22.5 t
• Bridges also need to withstand the amplified effects of
dynamic loading, over-loading, vertical and horizontal shock
forces such as in areas where heavy vehicle braking occurs.
• From a structural perspective, heavier payloads do not
necessarily relate to greater relative bridge impacts.
• This is because in some instances the longer vehicle types are
able to spread their axle loads more evenly across the
structure or even bridge a short span length.
Road width requirements
• This measure considers the vehicle’s ability to remain within
the available traffic lane width along a straight road.
• This measure is influenced by variations in the road surface
due to cross-fall, unevenness and localised failures on
– increase the available lane width or
– construct a surfaced shoulder
Recent Survey Results
• Consistent with
• Main findings relate
– road lane width
– road surface
• As perceived by the
(as opposed to
E. How should traffic engineers
and planners respond
• Road Controlling Authorities and Councils are under severe
pressure to maintain the condition of our roads. This effort may
be diverting funding away from other areas of greater need.
• The advent of larger vehicles have the potential change many of
our previous assumptions about vehicle performance and how
they impact on our roads.
• More needs to be done towards encouraging the use of the
right size of vehicle for the right size of job, especially if there a
viable parallel alternative available, such as rail.
• Bigger trucks might be more efficient, but they are also having
an impact on the behaviour of other drivers and the perceived
level of safety associated with the driving task when combined
with other smaller vehicle types.
Banora Point Upgrade, New South Wales, Australia
DERRICK HITCHINS National Sector Leader Traffic
and Transport Planning, SMEC Australia Pty Ltd
Senior Engineer, Advantia Transport Consulting Pty Ltd