Trams for improved aquatic environment, less plastic and rubber and chemical pollution in waterways and lungs.

Tram Green Road in Barcelona…..


Tāmaki Makaurau Aucklandis the largest city in AotearoaNew Zealand. Home to around 1.5 million people, it has been experiencing rapid growth and now houses around 30% of the national population. Congestion is a hot topic in the media with estimates that it costs the city up to $1.3 billion (NZD) annually, or around 1.4% of the GDP. While undoubtedly this congestion is due to growth, it has roots in several historic decisions made in the 20th century. In the 1950’s and 1960’s, Tāmaki Makaurau Auckland’s once extensive tramways were removed and replaced with trolley buses. At the same time, a decision was made to focus on building a motorway network at the expense of extending the commuter rail system.

Now, a light rail network has been proposed to alleviate congestion and help enhance community connection for several different routes (ironically, down some of the very same tram routes removed 70 years ago). The first of these is the connection between the city center and the international airport, an approximately 20km line that will access areas expected to host around 17% of the population growth and 33% of the job growth occurring in the next 30 years2 (Figure 2).

Figure 2: Potential Auckland Light Rail route showing two different central
alignments, to be decided. City centre is at the north end of the route,
airport is at the south end. Contains data sourced from the LINZ Data
Service licensed for reuse under CC BY 4.0

Essential Freshwater Reforms

Recently, new national water management legislation has provided a driver to turn this light rail route into a biophilic transport asset that can provide not just improved access, but a myriad of other benefits as well. The new national direction governing water management for Aotearoa New Zealand are the Essential Freshwater reforms. They demand immediate improvement to our freshwater systems and the need to bring waterways to a healthy state within a generation. Te Mana o te Wai (roughly translated: the power/authority of the water) is the central concept and sets out the directions local body authorities (city, district and regional councils in Aotearoa New Zealand) need to take to improve waterways. Key to this are the principles of governance and stewardship, where those with authority must prioritize (improving and enhancing where required) the health of waterways now and into the future to ensure the needs of future generations are sustained.

To give effect to Te Mana o te Wai, councils must apply the following hierarchies of obligation: 1) the health and well-being of water; 2) the health needs of people; and 3) the social, economic and cultural well-being of people and communities. Following such directions, it can be reasonably interpreted that councils should take steps to ensure that infrastructure supports Te Mana o te Wai. For transport, this means building infrastructure that firstly has low pollutant generation and secondly can actively treat pollutant loads by sequestering contaminants within its structure, ensuring any discharged water is filtered and cleaned before entering the receiving environment.

But, our current transport paradigm remains inherently polluting. Centering cars and private vehicles in our urban spaces creates swathes of impervious surfaces. This results in “Urban Stream Syndrome”, where paved areas create faster runoff, leading to streams that have higher flood peaks and more erosive power, transport more pollutants and sediment, and have fewer species and less complex ecosystems. Compounding this is the fact that the more we drive, not only do we require more impervious surfaces to drive on, we also increase the number of tyres, which are major sources of heavy metals and microplastics, released to the environment as they wear. Tyres are 1-2% zinc oxide by weight, added during vulcanization to make tyres harder wearing and longer lasting. In Tāmaki Makaurau Auckland, zinc is a major contaminant in our marine receiving environments, where too much zinc creates toxic conditions for macroinvertebrates and small benthic organisms that are integral parts of the food web. Wear and tear on road surfaces from tyres is estimated to directly contribute 10% of all microplastics in the world’s oceans.

None of the above is new. Auckland Council recognizes that roads carrying more than 10,000 vehicles per day are high contaminant generating activities. To mitigate this, such roads should have treatment devices within the corridor that can do a mix of reducing pollution and runoff. Yet retrofitting existing roads is challenging because these treatment devices generally take up more room than is available without a drastic reshaping of the corridor. Changing our vehicle powertrains from internal combustion to electric or hydrogen will not address tyre wear, or reduce impervious surfaces either.

Knowing that we need to improve our waterways but continuing to design systems for cars that create toxic freshwater environments leads to incompatible outcomes. The requirements of Te Mana o te Wai legislation will place responsibilities on local government that creates conflict with building roads as normal. Application of biodiversity net gain concepts can help explore the choices we face (Knight- Lenihan 2019). We need to ask the question “What would urban transport look like if the fundamental requirement was a net-gain in water quality?