Why building motorways can be daft

I’m reading an excellent book at the moment – Resilient Cities by Peter Newman, Timothy Beatley and Heather Boyer. I commented on this book a few posts ago, with particular reference to how pathetic our preparedness for peak oil is and how stupid Treasury’s oil price predictions are. I have just got up to reading the chapter which relates to transportation issues, and there are certainly some interesting points in it.

The basic premise is that for a city’s transportation system to be resilient – that is to be able to adapt to the changing world that we face over the next few decades – it simply can’t be as auto-dependent as many American cities, as well as Auckland, are at the moment. Whilst electric cars may come along and be the answer to our problems at some point in the future, to properly ensure that the effects of peak oil and climate change are not too horrific there is simply no alternative to making cities more public transport oriented.

One point that I found particularly interesting, before I get on to explaining the pointlessness of building more motorways, is the relationship between increased public transport use and decreased car use. Often it is simply thought of as a one-to-one relationship: that each increased ride for public transport is one fewer trip made in the car. However, it appears as though the relationship is actually stronger than that: that “there is an exponential relationship between increased transit use and declining car use.” This is further explained:

This helps explain why use of cars by inner-city residents in Melbourne is ten times lower than that of fringe residents, though transit use by inner-city residents is only three times greater. The reason is that when people commit to transit, they may sell a car and even more closer to the transit, eventually leading to lan use that is considerably less car dependent.

It is probably too early to tell, but perhaps it is this phenomenon that goes some way towards explaining some of the traffic patterns around Auckland over the last year and a bit. After the Northern Busway opened last year there was a significant increase in the number of people using public transport on the North Shore, but a far MORE significant decrease in the number of people driving across the Harbour Bridge each day. Clearly, rising petrol prices had a lot to do with lower car use (perhaps fewer discretionary trips were made), but perhaps people were starting to realise that with the Northern Busway in place they no longer had to live such auto-dependent lives. Over time, especially if we see some intensification around the busway stations, we may actually see this trend continue quite significantly.

Anyway, onto the main purpose of this post: to question whether building motorways really actually ends up achieving the purpose of what they were trying to achieve. Now, for a start, I must say that having spent a decent amount of today driving around on Auckland’s motorways I definitely do see a use for them: in shifting people around long-distances within the city fairly quickly – especially on weekends when the traffic flows are less concentrated and more all over the place. However, as I am certainly not advocating we get rid of any of Auckland’s current motorways, the question is mainly around “should more be built?” While Resilient Cities doesn’t mention Auckland specifically, some of the points it makes would certainly apply here – especially when considering many of the arguments put forward in support of the Waterview Connection.

Now, motorways are usually proposed to help ease congestion, and are considered to save time, fuel and emissions by avoiding the stop-start nature of driving on local roads. As we all know, cost-benefit analyses are used to justify motorways, largely based on these ideas. Resilient Cities strongly questions the supposed benefits of this approach to justifying the money that is sunk into motorway projects:

Will it really save fuel to build freeways? No, the data do not support these contentions. The data show that cities with higher average speeds use more fuel per capita as the faster roads just mean people travel farther and more frequently by car. Is congestion associated with higher fuel use in cities? No, on the contrary those cities with lower congestion use the most fuel. Although individual vehicles in less congested cities are moving more efficiently they are being used much more often and for longer distances while greener modes are being used less.

In my opinion this is the crux of the issue, at least to some extent, in that induced demand is often ignored when planning road development. Furthermore, by ‘demonising’ congestion, we ignore the fact that congestion is actually a pretty good indicator that we need to offer better alternatives to the car: rather than just providing more capacity for cars. It is congestion of the road system that – as long as alternatives are available – will give people the incentive to use those alternatives. We needn’t destroy our cities by fighting and endless battle of providing more capacity, watching that fill up, having to provide more capacity and then watching that fill up too. This is further elaborated upon in Resilient Cities:

Is removing congestion always a good thing? Not if it is attempted by increasing road capacity; car use will increase to quickly fill the newly available space. The Texas Transportation Institute, in a study of US cities over the past thirty years, found no difference in the levels of congestion between those cities that invested heavily in roads and those that did not. It is possible to make more car dependence and congestion out of a policy to improve traffic.

It certainly seems like this is the mistake Auckland has made over the past few decades – and in particular in the last decade where it seems like we’ve really tried to build our way out of congestion. Somewhat ironically, the only thing that has ever really had a major effect on reducing congestion in Auckland over the past decade has been rising petrol prices.

With $1.4 billion likely to be sunk into the Waterview Connection over the next few years, as well as $430 million on the Victoria Park Tunnel, $300+ million on the Manukau Harbour Crossing Project, $200 million on the Newmarket Viaduct replacement, around the same on the Hobsonville Deviation and the SH20-SH1 project, it’s pretty clear Auckland hasn’t yet learned that you cannot build your way out of congestion.

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