Concrete roads well suited to high intensity traffic
by Gareth Kiernan, Chief Forecaster, Infometrics
The report looks at roading costs in New Zealand and considers extensive research overseas. It shows that although concrete roads cost more to build, savings can amount to millions of dollars for central government and councils as maintenance costs are up to 62% lower. Lifetime carbon emissions for concrete roads may also be better than tarseal because concrete reabsorbs carbon dioxide.
Lack of capability has been a major limitation for concrete roading in New Zealand. The Government could play a role to overcome this hurdle, for example by funding a pilot project. Expanding the industry’s capability to be able to build concrete roads, with their extra resilience, could also be increasingly important as heavier electric vehicles become more common.
Given that approximately one in two highways in United States are built using concrete, concrete roads should complement existing roading typologies. Concrete roads are best used in applications where there are high traffic densities and areas of high stresses from heavy vehicles. There are a number of stretches of road where concrete would save money and time, such as Auckland’s Port Motorway, the Cambridge section of the Waikato Expressway to the intersection of SH1 and SH29 at Piarere and SH1, North of Levin.
Our report shows concrete roads could have a lower carbon footprint over whole-of-life than asphalt if carbon uptake is taken into account. Carbon uptake is a natural process by which exposed surfaces of hardened concrete absorb atmospheric CO2 over time. Emissions associated with concrete roads can be even further reduced by using low carbon concrete. In addition, concrete can be recycled.
Concrete roads are rigid and therefore can reduce fuel consumption and, as our summers grow hotter, concrete roads don’t melt. While concrete will not suit every roading purpose, it certainly deserves more consideration than has occurred to date in New Zealand.
At the recent launch of The Case for Concrete Roads report at the Future Roads conference, Hamilton Mayor Paula Southgate said the city recently trialled roller compacted concrete on Arthur Porter Drive, a busy industrial road with unique construction challenges. She said the early results are promising and show concrete is a smart and sustainable choice for future projects.
Our report summarises selected international comparisons of concrete and asphalt roading costs. The consensus is that concrete roads are almost always more cost-effective than asphalt roads over a life of 40 years. Cost variations in different countries arise due to differing labour and other input costs, the type of asphalt or concrete technology, the discount rate used when calculating costs over whole of life, and the differing life span of roads.
We drew on this data, and available New Zealand data, to run 20,000 computer simulations of roading construction and maintenance costs in New Zealand. The result is a 12% to 23% advantage in costs to concrete over asphalt for the central 90% of the distribution of results. The weighted mean is a 17% cost advantage to concrete.
