DCSS – Pedestrian Bridge Design FAQ

The typical price for a pedestrian bridge in NZ ranges from NZ$3000/SQM to NZ$9000/SQM with an average of around NZ$4000/SQM. These estimates are inclusive of design and construction costs. In most cases, we would recommend that budgets for a simple pedestrian bridge are set assuming a likely cost of NZ$3000 to 4000/SQM where spans of between 15m and 25m are expected. Allow NZ$5000 to $6000/SQM in the range of 25m to 40m.

If your span exceeds 40m the complexity of the bridge will increase and a cost closer to NZ$7000 to $8000/SQM is more likely. The upper end of the NZ$9000/SQM comes into play where you have extreme site constraints or where you require significant architectural improvement and/or architectural feature lighting is added.

As an example our Laurent Swale Footbridge has an approximate cost of circa NZ$3000/SQM and our Water of Leith Cable Stayed Footbridge had a price of circa $7500/SQM. The first is a simple steel footbridge of 25m span x 3m width, the second is an architectural cable stayed footbridge of 45m span x 3.5m width incorporating architectural feature lighting.

The bridge span is the “clear distance between the vertical supports”. Bridge span should not be confused with “bridge length” which is the total distance of a bridge from end to end (measured along the deck). For example, a 50m long bridge with a support in the middle will have a span of 25m.

District Resource Consent
Generally speaking in NZ your pedestrian bridge will require a Resource Consent from the District (or City) planning authority (i.e. the local Council) to cover the disturbance to land from building the foundations (the cost of this process can be obtained direct from the Council). This process is likely to take 6 weeks.

Regional Resource Consent
If the bridge crosses a water body such as a stream, river, coastline there is a likelihood you will need a resource consent from the Regional Council. However, the scale of this process can be greatly reduced if your span is modified/increased to prevent the need for any permanent footbridge in the water (outside of 1/50 flood zone for a river and/or the high tide mark for coastal locations). This process is likely to take 6 weeks (but can run in parallel with District Resource Consent).

Building Consent
Assuming you have qualified structural engineers and geotechnical engineers designing and supervising your project and issuing the required “Producer Statements” for their work, you can apply for a Building Consent Exemption. We have done this on several pedestrian bridge design projects throughout NZ. This is totally dependent upon the processing Team at council who must formerly accept the exemption. This saves a lot of time and cost otherwise associated with BC sign-off.

We recommend a design life of 100 years be adopted if possible for pedestrian bridges and cyclebridges to maximize your long-term return on the investment.

50 years is the minimum design life permitted in NZ (to be NZ Building Code compliant). However, the design standards also provide guidance for design to 100 years. 100 year is the minimum requirement for design to the NZ Transport Agency Bridge Manual and is regarded best practice.

The primary factor when considering the overall design life question of “50 years or 100 years?” is not necessarily the maintenance of the materials, but it is instead the scale of extreme events that the bridge will need to resist during its life. The longer the bridge is in place, the higher the probability that it will be subjected to larger scale “extreme events”. Extreme events include earthquakes, high winds, and/or flooding. For example, a pedestrian bridge designed in NZ for a 50-year life must be designed for an earthquake that has the probability of occurring once every 500 years, whereas a pedestrian bridge designed for a 100-year life must be able to resist an earthquake that might occur once in every 1,000 years. This is a big step up in load and is equivalent to about 30% more lateral demand from the seismic forces and/or displacements being considered. Wind and flooding demands are treated in a similar way.

See below the info relating to considering climate change where your bridge crosses water.

If your bridge is crossing a waterway that you will need to consider the influence of long-term climate change. Climate change is expected to increase both sea levels and rainfall. Typically we see an allowance of +250mm and +500mm increase in current day water levels to accommodate a 50-year and 100-year bridge design life life respectively. Regional Council and/or an independent hydrologist can confirm these values for the specific body of water you are dealing with.

Some interesting information on Climate change in NZ can be found at the Royal Society. Land information NZ (LINZ) is also an important resource for photographic imagery, flood information, and topographical information in NZ.

The recommended inspection regime for bridges frequented by the public is a “General Inspection” every 2 years and a “Detailed Inspection” every 6 years. These can be performed by inspectors experienced in either bridge inspections and/or bridge design. These inspections will identify any required maintenance activities and will often include likely cost estimates and time scales for repair.

For advice relating to bridge inspection we recommend you take a look at the Bridges, geotechnical structures and other significant highway structures inspection policy (NZTA 2019).

Yes! In 2017 we developed “The Standard NZ Footbridge Design” for use in NZ. The set is a simple and cost effective footbridge solution for use in parks and urban landscapes. The bridge design is a steel beam system supporting timber joist and decking. The footbridge can carry pedestrians and cyclists and allows spans of up to 18m and usable widths up to 3m. The design is intended to help designers who need a simple, cost effective bridge for their overall masterplan but who do not want to commission a bridge engineer or bridge architect in the early stages.

See more info and download the drawings from here.