Clearly, New Zealand needs a viable plan in order to deal with its urban problems, especially housing affordability and congestion.

But whether intensified, compact development should be pursued, on the basis of greater health benefits in particular, is far from clear.

The latest report by The New Zealand Initiative, Up or Out? Examining the trade-offs of urban form, provides an in-depth analysis of the economic and social costs of both upward and outward development from a transport, land, housing, agglomeration and health perspective.

The release of the report comes as more and more cities around the world, including New Zealand, are focusing their future development on a more intensive use of space as opposed to spatial extension.

Proponents of the compact city philosophy argue that residents will be healthier and fitter than their suburban counterparts because a more compact urban form will encourage walking and cycling rather than driving.

However, international empirical evidence shows that the link between urban design and physical activity is weak. Hong Kong and Singapore are often used as prime examples of compact cities, but both are burdened by high obesity rates. And despite high use of pedestrian networks and extensive public transport infrastructure, their residents undertake insufficient amounts of physical activity, according to the World Health Organisation.

Secondly, compact city advocates also posit that by encouraging walking, cycling and public transit usage, the production of, and exposure to, airborne pollutants will be greatly reduced.

Yet, more intensified urban forms are more often associated with greater traffic congestion and higher concentrations of nitric oxide and ozone than less dense suburban areas. Toxicology reports show that long-term exposure to these pollutants can result in nausea, throat and lung infections or on a more acute level, mental confusion, delayed pulmonary oedema and cyanosis.

Thirdly, there is a perception that compact cities might provide inner-city green spaces, which could have positive benefits for the mental and physical well-being of their residents.

However, it is logical that a densely developed and populated city simply cannot host the same variety or volume of flora and fauna as lower density urban fringes.

This is not to say that compact cities do not deliver at least some benefits. But, when set against the astronomical costs of radical change to urban form, a preference for compact development based on perceived health benefits is clearly overstated.

Khyaati Acharya is the co-author (with Jason Krupp) of the report, Up or Out? Examining the Trade-offs of Urban Form, which can be downloaded here.