Heavy Haulage

Providing local roads for the oversize transport

By Jonathan Bhana-Thomson, chief executive, NZ Heavy Haulage association.

The specialised sector of transport industry that moves large oversize freight provides a valuable service to the development and maintenance of Local Government assets, but in order to do so, there has to be provision of suitable designs, roads, and routes to cater for the transport of these loads.

There are a wide range of ways that the oversize sector help to provide service directly to the local body sector, these include:

  • Roading replacement – such as bridge beams and construction equipment.
  • Roading maintenance – the transport of large milling and resurfacing equipment.
  • Pre-fabricated items for construction and development projects such as treatment plants or civic facilities – such as concrete tilt slabs.
  • Infrastructure improvements – such as for provision of the three waters, utilising large construction equipment and prefabricated pipes and alike.

Then the oversize transport industry provides transport services to clients in local body areas as diverse as property developers, forestry owners, schools for relocatable classrooms, private clients for swimming pools and many other examples.

For these reasons it is important that suitable routes for oversize loads are provided. These routes need to be provisioned in terms of: Width and height clearances; bridge capacity; and design of roading infrastructure such as roundabouts, pedestrian refuges and speed tables.

Oversize loads will primarily use state highways to travel between the origin to the destination, but most often the delivery point will be located in an area where use of local body roads will need to be used. In addition, there are some cities where the state highway routes through an area will not able to be utilised for oversize freight due to existing restrictions on these roads (such as low overbridges), and local roads will need to used as a key part of the route.

One major example is in Auckland where the majority of the oversize route is on local body roads as the Motorway is not permitted for use. Another example is low railway overbridges – for example on SH1 there are local road bypasses at Tirau and Marton. Finally in places like Dunedin the northern motorway can’t be used due to the low overbridges and Mt Cargill Road must be used instead.

Routes and design for oversize

Where there are local body roads that need to be used, then Council’s should be identifying this in their transport plans and preserving them so that they can be used for oversize loads. This means that design of things such as roundabouts, gateway road speed signs, traffic signals, roadside and overhead signage, and pedestrian refuges need to be designed with oversize in mind.

A recent development has been the much greater use and investigation of speed tables to control the speed of all traffic. For oversize loads, the height of the table should be no more than 80mm, and the approach ramps need to be 1:15 to allow for the ride to even and not produce too much extra noise for any local residents. Consultation with local heavy haulage rep’s or the Association is key to ensuring that the design is suitable for oversize loads.

Maintenance of routes

Once identified and designed for, then it is key to preserve these routes through ensuring that the envelope provided is able to be sustained over time. This includes such things as maintenance of the trees and vegetation that is adjacent to the roadway so that width and height clearances are not impinged on. In addition, where the roading surface is to be replaced, that where there are overhead restrictions – such as overhead signage, overhead traffic signals or overbridges and footbridges, that the surface is milled out and replaced, so that precious height clearance is not lost.

Finally, a common problem for local government is that many of the bridge stock was constructed some time ago, and the capacity of some bridges can deteriorate over time. It is important to identify those bridges that are on critical oversize routes to ensure that these bridges and monitored and where possible strengthened or replaced.

Safety and enhancement

A recent development has been funding being available for additional safety changes to roads, or enhancements for walking and cycling. These changes when they occur on local oversize routes need to be designed with oversize loads in mind – and while at times this can be challenging to accommodate, through consultation and working together good outcomes for all parties can be achieved.

The overall message is that provision and maintenance of local government roads for oversize where required is important, and this can be achieved through collaboration with the oversize freight sector.


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