The land transport infrastructure network encompassing road pavements and bridges is being constructed and managed to withstand a variety of conditions imposed on it. One of the most important of these conditions is vehicle loading.
The Austroads Guide to Pavement Technology Part 2: Pavement Structural Design contains procedures for determining traffic loading for the design of a broad range of flexible and rigid pavements. A road pavement must be strong enough to cater for both the heaviest of these vehicles and the cumulative effects of the passage of all vehicles.
The WIM survey data can provide the following necessary information for pavement design:
- lane-specific heavy vehicle traffic loading data across a carriageway
- initial daily number of heavy vehicles
- the number of axle groups per heavy vehicle required to estimate the cumulative number of HVAG
- the distribution of axle group types and loads required to calculate the design traffic for flexible pavement and rigid pavements
- the TLD.
Austroads 2000 provided some special cases to quantify the financial benefits or return to the Australian road infrastructure network via WIM technology.
In the past, for Road Functional Class 6 roads, the New South Wales value of 1.9 ESAs per commercial vehicle was used in initial and rehabilitation designs in Canberra, whereas an ESA value of around 1.0 via the WIM surveys was found to be more appropriate.
In a 600 metre long, two lane carriageway requiring rehabilitation work, this result produced a saving of $12 000.
TMR 2002 also provides some details of the Queensland overload management system.
Applications of heavy vehicle mass data for the development of infrastructure asset design and management can be summarised as:
- bridge management and design strategies
- pavement management and design strategies
- determination and adjustment of loading criteria for bridge codes
- dynamic loading effects on bridges
- input into pavement and bridge management systems
- knowledge of axle configurations and IAM for derivation of group average ESAs
- for commercial vehicles and axle configurations, furthermore, information on the number and types of heavy vehicle axles
- assessment of road pavement wear
- modelling pavement response and overall performance as a result of applied vehicle loads
- spatial repeatability – measurement of systematic (repeatable) patterns of axle impact forces along pavements
- enhanced risk management and reliability in pavement design
- gathering important traffic volume and composition data which allow mass/loading characteristics from a WIM corridor to be attributed to a wider road network
- investigation of premature deterioration of specific road pavements and bridges, encompassing the collection of heavy vehicle mass data for specific rehabilitation and maintenance designs
- triggering the switching on of exhaust fans in tunnels, not as a result of the build-up of CO2 and other emissions, but rather on the use of tunnels by heavy vehicles.
Austroads 2012, Guide to pavement technology, part 2: pavement structural design, AGPT02-12, Austroads, Sydney, NSW
Austroads 2000, Weigh-in-motion technology, AP–R168-00, Austroads, Sydney, NSW
Department of Transport and Main Roads, Queensland 2002, Queensland asset maintenance guidelines, part 3: overload management system, Queensland Department of Main Roads, Brisbane, Qld