Let us play a game of spot the odd one out. Which of the following has the highest level of traffic congestion: New Zealand, Australia, Canada, Western Europe or the United States?

The answer, surprisingly, is New Zealand according to an article on the New Geography blog. Quoting the latest Tom Tom Traffic Index figures, the story claims the average urban road journey in New Zealand takes 31.3 per cent longer than it should. Expressed in real terms, that means a 30 minute car ride will take 40 minutes.

Auckland’s traffic issues rank it in the top 10 most congested Western cities. Christchurch and Wellington do not fare much better, coming in 12th and 24th respectively. That is staggering when you consider that New Zealand is far less developed, and has a lower urban density, than almost all of the countries examined.

Looking at these figures, some might say they justify a move to reduce car usage, and steer development towards public transport options. However, the Tom Tom data should be read with caution.

Firstly, looking at Tom Tom’s list of most congested metros, it is noticeable many of the gridlocked cities (Marseille, Palermo, Vancouver, Rome, Paris, Stockholm, Los Angeles) have invested heavily in public transit infrastructure, some even for decades. So, why are they so congested?

One explanation is that the personal utility of private vehicle travel is so great that rail and other forms of transit are poor substitutes. This was demonstrated in Portland, Oregon, where light rail usage failed to achieve its stated targets, and three out of every four passengers were cannibalised from bus routes.

A better fit is that New Zealand has underinvested in its roading infrastructure. As far back as the 1960s it was identified that Auckland needed three bypasses. To date the city is only serviced by one major bypass. Plans to construct the Eastern bypass were scrapped a few years ago, and the Western bypass, State Highway 20, is only now being constructed.

The shape of our cities plays a major role. Auckland’s hub and spoke model means you have to virtually travel into the CBD to get through or around the city, and it is similar in Wellington. Still, at least both these cities have major highways. Christchurch’s southern highway only services a tiny fraction of the city.

This apparent under-investment needs to be seriously considered when we assess congestion in places like Auckland. Next time you are sitting in rush-hour gridlock ask yourself is it because private cars are flawed as a model, or because road construction never kept pace with the growth in population and the economy?