This is a guest post by Caroline Shaw, Ed Randal, Alistair Woodward and Michael Keall
NZ is the most car dominated country in the world, but transport patterns vary across our urban centres. The six largest NZ cities have had different histories and priorities, which over time, has led to quite diverse transport arrangements (see Table 1). Note the higher proportion of trips taken by bicycle in Christchurch, walking is most common in Dunedin and Wellington and levels of public transport are highest in Wellington.
We recently published a paper in the New Zealand Medical Journal (open access after September 2018) which has estimated the effects of these differences in transport systems on the health of citizens and greenhouse gas emissions. Specifically, we asked what would be the benefits for residents of Tauranga, Auckland, Hamilton, Christchurch and Dunedin if these cities had the same mode shares of sustainable transport as Wellington City (where around 35% of trips are taken by walking, cycling or public transport).
This research was undertaken using the Integrated Transport and Health Impacts Model (ITHIM) which was developed in the UK, and adapted for New Zealand by the researchers from the Universities of Otago and Auckland. Briefly, it consists of three parts, an injury model, an air pollution model, and a physical activity model (these are the main pathways through which transport impacts on health). Mortality (deaths) and morbidity (cases of disease) caused by transport-related injury, air pollution and physical inactivity are calculated based on the current transport patterns of the six NZ cities. Carbon dioxide emissions from light vehicles were calculated using kilometres travelled by cars, vans, 4WD, utes and small trucks in each city and average fuel use per kilometre. We then assumed the mode share of all cities was the same as the current spread in Wellington (table 1). Using ITHIM we calculated the effects of this new scenario on levels of transport-related physical activity, air pollution, injury and kilometres travelled in those cities, and hence changes in health outcomes and carbon emissions.
The results of this ‘Wellington’ scenario on premature deaths avoided and carbon emissions reduced are shown in Table 2 (the disability results can be seen in the full paper). All cities would reduce the number of people dying prematurely. Auckland, Hamilton and Tauranga could reduce premature deaths by 49-57 a year. Light vehicle carbon emissions would reduce by 20% in Auckland and 32% in Hamilton. Most of the health gain arising in the other cities as a result of shifting to Wellington’s transport patterns would be due to increased physical activity in the population (from more walking and cycling), but also importantly due to reduced injury. This may seem counter intuitive since we know that cycling or walking has higher injury risks per km than travelling by motor vehicle (and this model does take that into account). However, getting people out of vehicles into other forms of transport is good news for everyone, since fewer vehicles on the road mean fewer crashes resulting in death or injury.
We are not arguing that the Wellington transport system should be the one that other cities in NZ aspire to. Indeed, the scenario rather improbably assumes reduced levels of cycling in Christchurch; and we know that cities globally have been able to achieve far greater increases in sustainable transport levels than those that are modelled here, often in short time-frames (e.g. Vancouver). But getting close to the Wellington mode share would, in most respects, be a welcome first step, and is clearly feasible.
This study showed that to get the biggest health gains policies should promote walking and cycling but to get the biggest improvements in greenhouse gas emissions, public transport is the key. Ideally cities should have a balanced transport portfolio – all three of these modes should be prioritised. The carbon emission reductions in this model only include averted tailpipe emissions from small vehicles. They don’t take into account any extra emissions from fossil fuel powered public transport. However neither does it take into account that many of the trips avoided in the ‘Wellington’ scenario would be the short, least fuel efficient trips and any savings from reduced vehicle ownership in those cities and the embodied carbon associated with production and end of life destruction of vehicles.
This research shows how important it is for cities to take into account the health impacts of the decisions they are making around transport. These numbers are not trivial; about 200 premature deaths per year could be avoided with this scenario. This is equivalent to around half our annual road toll, and not dissimilar to the number of deaths we might expect a colorectal cancer screening programme to prevent each year. Local and regional councils need to more explicitly account for the health and environmental impacts of their decisions (using a model like ITHIM is one way they can do this).
We have had a transformation in our thinking about housing in the last decade. Housing is now more than just a roof over our heads, housing is something that keeps us warm and safe and healthy (in an ideal world). We need to have the same transformation for transport. As well as moving trucks and people, it’s about creating cities we want to live in, about meeting our carbon reduction commitments and about improving mental health and cancer prevention.