From their council offices, looking down on the choked roads of Auckland at rush hour, it is easy to see why planners see rail systems such as the City Rail Link as the most viable solution to congestion.
 
Certainly, trains are an important public transport option. The world’s most impressive rail systems are a means of fast and efficient travel, and are not prone to some of the issues faced when using road transport.

But just because it is appealing in theory doesn’t mean it actually works in real life. This is one of the surprising finding we discovered in our latest report Up or Out? Examining the Trade-offs of Urban Form.
 
International research appears to suggest metropolitan train services have a limited effect upon a city’s traffic problems. For example, quantitative analysis conducted by the Reason Foundation, which examined 26 years of congestion and transit investment data across 74 of the biggest metropolitan areas in the US, found that trains don’t cure gridlock.
 
The research found there is no statistically significant link between investment in public transport infrastructure and meaningful declines in traffic congestion in the long term.
 
This may sound surprising, especially for residents of cities who have been told that rail, light rail, and trams are the solution to choked highways. Yet the Reason Foundation study has hit on a truism of modern transport: public transit will never be a perfect substitute for private vehicles.
 
This stands for many reasons, the first being that public transport, and trains in particular, do not cater well for an individual’s social behaviour.
 
Even the world’s most impressive rail systems reach fewer destinations and are less frequent, flexible and often less safe than private vehicle travel. Many people, particularly women, are reluctant to choose public transport options over private vehicle travel at night because of safety concerns.
 
Second, most rail systems are laid out in a hub-and-spoke network with the most frequent services being from the suburbs into the city centre. Yet, there is an inherent limitation in this type of layout, as it assumes a city’s residents have the same travelling patterns.
 
In Auckland, for example, only 13% of the city’s working-age population are employed in the CDB. And neither is this unique. Even in a dense conurbations like the New York tri-state area, only 26% of computing trips take place between the suburbs and the CBD.
 
Clearly train networks, which service a hub-and-spoke urban structure, are ill-suited to service the transport needs of people who want to access facilities that are not situated on a transport corridor; like schools, kindergartens, shopping centres and so on. This means that groups in society, like working parents, are unlikely to opt for public transport over the family car.
 
Third, there is the limitation posed by rail catchment zones. This is the maximum area around a railway station within which people choose to walk or drive to the station and catch a train, rather than drive to and from work.
 
That means that those who live beyond the average catchment area are more likely to choose private cars to commute since the inconvenience of congestion is only marginally greater (or even less) than the hassle faced by public transport.
 
Within greater Auckland – a total land area of 4,894 square kilometres – there are 130 kilometres of rail line consisting of the southern, eastern and western lines. There are around 40 stations in total along these lines, including major hubs like the Newmarket station as well as minor stops like Takanini and Homai.
 
Calculating the combined walking catchment radii of these stations equates to around 520 square kilometres; this means that only 10.8% of greater Auckland falls within a pedestrian rail catchment zone.
 
The various problems with public transit put paid to a notion within compact city ideology that solely investing in public transport infrastructure is the silver bullet solution to congestion woes.
 
As the Reason Study shows, over the last 30 years, there has not been one example where major public transit investments have meaningfully alleviated congestion in US cities.
 
This is not to say that public transit is unimportant, but rather that rail networks are a critical component of a greater mixed transport model that is needed to ensure efficient, safe and flexible travel within any city – not the only component worth investing in.
 
What is needed are far more nuanced solutions, consisting of different transport options that are tailored towards population patterns within a city, what it can afford, and most importantly, what its residents want.

It would be naïve to assume that all readers will agree with this statement, but we welcome robust debate on the topic.
 
We hope our report, and the evidence we present, redefines the terms of engagement and encourages a far more open and informed debate on how New Zealand’s cities grow and develop. And at the very least, we want it to make fact, not ideology, the basis for future discussions on urban forms changes.