Local Government Magazine
Infrastructure

Designing and operating roads for oversize

designing and operating roads for oversize

The way that our roads are planned and managed is to try to suit the majority of road users to keep them safe and to operate efficiently. Jonathan Bhana-Thomson, chief executive, NZ Heavy Haulage Association comments.

In recent years, the push towards planning for more vulnerable road users such as cyclists and walkers has grown in momentum. However it is also the case that all road users need to be considered – and while the transport of large oversize loads is a small percentage of the overall traffic on roads – there needs to be definite plans for how roads are designed and operated to facilitate the transport of these loads. 

There is increasing demand from clients, customers and for government projects, that oversize loads – be this large equipment, prefabricated components, or new or recycled buildings – need to be moved around the country.

Often this can be locally, but there are also many examples of large indivisible items be shifted. 

In order to facilitate this, roads need to be planned and managed so that this can happen with safety and efficiency, and there are some practical ways that roading owners and managers can ensure that this happens.

Identify oversize routes

A simple question – is the road that is being managed, operated or developed one that is used by oversize loads? 

If is it a State Highway, then assume that it is, but there are many arterial routes and local bypasses that have to be used. For example in Auckland most oversize loads are not permitted to use the motorway, so have to use local Auckland roads. 

In other areas, such as the Manawatu, over-height loads cannot fit under the rail overbridge near Marton on SH1, so have to deviate through Marton town instead. 

The next question is whether it is a key route or a secondary route. That is to say, is it the only route through the area for oversize loads – so therefore it is more crucial to maintain it. 

The easiest way to check whether a specific route is an oversize route is to check with the NZ Heavy Haulage Association, as we have the most up to date information.

Design for oversize

Often the specialist vehicles that are used to transport loads, as well as the loads themselves take up a lot of space on the road. 

There are many safety requirements for the actual transport of the loads themselves, but the roads need to be designed to cater for oversize loads. The association has a Road Design Specification available from its website, which details the requirements that are sought in general, but the value comes in actively discussing individual projects with the Association, so that we can analyse them from the transport operators’ perspective. 

The outcomes for road owners are that the road will cater for oversize loads, they will be able to be transported more safely, and there is likely to be less damage to roadside infrastructure if these are placed in locations that do not impose on the over-dimension transport zone. 

Maintain for oversize

Once a road is operating, whether this is a new stretch of road, or one that has been in place for many years, there is always maintenance requirements for that section of road. 

This may include the road surface, the signage or other similar roading infrastructure, as well as maintaining any roadside and overhead vegetation. Road owners will need to specify in their contracts that the height and width clearance on oversize routes will need to be more than for standard freight routes (see our specifications for guidance). 

In addition, when maintaining the road, then any of these works will need to take account of the fact that oversize loads may not be able to use detour routes, or narrowed lanes, and so specific provision should be made in any traffic management plans for how to manage oversize loads – the same as provision may be made for pedestrians and cyclists. 

The combination of these three steps will see this small but important sector of our freight sector catered for. 

It is in the interests of those who own, operate and maintain roads that provision is made for oversize loads proactively, as this will produce the best outcomes.


This article was first published in the April 2021 issue of Local Government Magazine.

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