If you’ve ever visited a wind farm you could attest to the fact that the wind turbines are much larger than most people would imagine. The height of the complete structure is awe inspiring with the wind blade sometimes measuring up to 90 metres in length. Many would ponder how such a large component is lifted into its operating position, but some may also consider the complexity in getting the wind blade to the site itself. You may have been on a road where escort vehicles are managing traffic around a large, slow moving vehicle with an oversize and overmass (OSOM) load. However, before getting to the task of transporting the loads to the site, traffic engineers work many hours on planning and assessing the route to ensure this important part of the project runs smoothly.
Part of a renewable energy project’s approval process is the Traffic Impact Assessment which includes a heavy vehicle and high-risk OSOM vehicle route assessment. From B-doubles to varying platform trailer combinations and beam sets which are more equipped for OSOM loads, each vehicle and load will have unique characteristics that require assessment.
Road authorities dictate which vehicles are permitted to use which roads on their network. This ensures that roads continue to provide a safe environment for all road users and an efficient traffic flow is maintained. State road authorities mostly maintain freeways and arterial roads which have a higher capacity. Heavy vehicles more commonly use these roads. As roads become smaller such as collector, distributor and local access roads, local councils become the caretakers. Intersections and changes in the road geometry become more prevalent on these roads making the environment less conducive to heavy vehicle traffic. Therefore, conditions would apply for heavy and OSOM vehicles to use lower order roads if the size of the road would allow passage in the first place.
Road geometry obviously plays an important part in determining suitability for large vehicles using roads. In road design, minimum horizontal and vertical dimensioning exists to ensure roads are fit for purpose and that passage around corners, under bridges and through tunnels is possible and safe. Additionally, weight loadings are also considered in determining a vehicle’s suitability on the road to avoid structural damage to the pavement, bridges and culverts. When considering height, width, length and mass of the vehicles and their loads, the available road network is reduced as the vehicle and load sizes increase. Obstructions on the network can often steer the route away from the most direct and consequently add hundreds of kilometres to the journey.
Above: Example of a typical route for an OSOM vehicle travelling between Sydney and Bathurst.
At Amber Organisation, we use ‘Swept Path’ software within AutoCAD to show how a vehicle of any size can manoeuvre through a road network. Standard vehicle sizes, as prescribed by Austroads, are used during road design and anywhere else vehicles are expected to drive. For the OSOM loads, a standard heavy vehicle may not be suitable, so we have the capability to design custom vehicles within the software to accurately represent the vehicle required for the project’s needs. Once the vehicle is set up in the software including important details such as turning radius and tail overhang, it can be ‘driven’ through the road network with aerial imagery as the background. The software shows how much space will be required for that vehicle to turn through tight sections of the road network. This will determine if the OSOM load can successfully make it through the pinch points or whether any upgrades to the road infrastructure need to be made.
Above: A 56 metre long OSOM vehicle navigating through an intersection using opposing lanes.
The finished route assessment provides details on the best route to the project site, temporary or permanent road upgrades that will be required prior to transit, how the transportation crew should navigate pinch points, what areas escorts and spotters should be wary of and locations of suitably sized rest areas for the driver and crew to stop in.
The team at Amber Organisation have strong experience and capability in producing Traffic Impact Assessments and Route Assessments for a wide range of projects. Please feel free to contact us if you require these services or any general advice in relation to traffic or transport matters.