Wired magazine recently published a good, succinct explanation of induced traffic. It’s worth reading in full as it hits upon an incredibly important, often overlooked fact: it’s not possible to eliminate congestion by building more roads. Here are a few of the more interesting excerpts:

The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more. Though some traffic engineers made note of this phenomenon at least as early as the 1960s, it is only in recent years that social scientists have collected enough data to show how this happens pretty much every time we build new roads. These findings imply that the ways we traditionally go about trying to mitigate jams are essentially fruitless, and that we’d all be spending a lot less time in traffic if we could just be a little more rational.

But before we get to the solutions, we have to take a closer look at the problem. In 2009, two economists—Matthew Turner of the University of Toronto and Gilles Duranton of the University of Pennsylvania—decided to compare the amount of new roads and highways built in different U.S. cities between 1980 and 2000, and the total number of miles driven in those cities over the same period.

“We found that there’s this perfect one-to-one relationship,” said Turner.

If a city had increased its road capacity by 10 percent between 1980 and 1990, then the amount of driving in that city went up by 10 percent. If the amount of roads in the same city then went up by 11 percent between 1990 and 2000, the total number of miles driven also went up by 11 percent. It’s like the two figures were moving in perfect lockstep, changing at the same exact rate.

Los Angeles: Sitting in traffic after ignoring supply and demand for over 50 years.

In their excellent paper on the topic, Duranton and Turner describe this as “the fundamental law of road congestion: New roads will create new drivers, resulting in the intensity of traffic staying the same.” Their research also digs into a couple of other related and equally interesting phenomena:

  • Better public transport provision doesn’t actually reduce road congestion – but it does enable more people to move without being affected by congestion
  • Reducing road capacity has no measurable impact on congestion – if less road space is available, people take public transport or active modes instead, or avoid making low-value trips.

Urbanist.co also has some further discussion of Duranton and Turner’s work. The economists go on to suggest economists’ favourite answer to congestion: road pricing. (If you’re interested in reading more about that topic, Stu Donovan and I have written several posts about the economics of road pricing.)

So what can be done about all this? How could we actually reduce traffic congestion? Turner explained that the way we use roads right now is a bit like the Soviet Union’s method of distributing bread. Under the communist government, goods were given equally to all, with a central authority setting the price for each commodity. Because that price was often far less than what people were willing to pay for that good, comrades would rush to purchase it, forming lines around the block.

The U.S. government is also in the business of providing people with a good they really want: roads. And just like the old Soviets, Uncle Sam is giving this commodity away for next to nothing. Is the solution then to privatize all roads? Not unless you’re living in some libertarian fantasyland. What Turner and Duranton (and many others who’d like to see more rational transportation policy) actually advocate is known as congestion pricing.

Incidentally, I like Turner’s “Soviet Union” metaphor a lot – I’ve said on occasion that we’re running our transport system like a Polish shipyard.

Lastly, it’s incredibly important to consider induced traffic when making policy recommendations. As I wrote in my review of Alain Bertaud’s talks in Auckland, keeping commute times down is an important part of maintaining an efficient urban labour market. Some people seem to have taken Bertaud’s recommendation that policymakers focus on keeping average car commutes under 30 minutes (and PT commutes under 45 minutes) as a call for more roads. This is a superficially appealing but deeply wrongheaded idea.

Induced traffic means that building roads to keep commute times down will not work. And it will be expensive. While there is often a good case for specific road improvements to remove key bottlenecks or improve safety – the Victoria Park Tunnel comes to mind – Duranton and Turner’s work shows that a strategy of building lots of roads will not succeed in minimising commute times. An alternative approach is needed.

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  1. A lot of good things here, but I’m not a big fan of the solution of congestion pricing. Congestion pricing means putting a price on people taking congested roads during congested periods of time. The big problem with it is that it doesn’t price non-congested highways, which may result in even more sprawl as companies flee to industrial parks in suburbs to avoid congestion charges. It also does nothing to avoid retail centers from placing themselves at highway interchanges, making them almost inaccessible to anyone not in a car.

    So I think that congestion pricing shouldn’t be done alone, you should also toll highways (motorways/expressways/whatever you call limited access high-speed grade-separated roadways). The reasoning is simple… I hope.

    First of all, speed is the main factor deciding what mode people will select in urban trips. For speed, highways are unbeatable, which yields great benefits to users.

    Second, highways are amongst the most expensive infrastructure projects around, for the same capacity, both regular roads, city streets and transit are much more bang for the buck.

    Third, if highways are funded mainly through gas taxes or other forms of taxes that spread the cost as widely as possible, then everyone will pay for them, whether they use them or not.

    So to sum up, it means that people are incentivized to use highways as they are the fastest way of getting around, even if they are the most expensive infrastructure. Not only that, but whether they use them or not, they will pay for them. Who would be dumb enough not to use them then? The benefit is individual, the costs are collectivized. You cannot reward waste and punish economy then expect people to self-regulate their use of a limited resource.

    Even worse, since everyone has to pay for them, whether they use them or not, it opens the door to a lot of people who say that since they pay for highways, they should have access to highways too, so if there is no highway in their region, then they will demand one be built. Else, they will claim that people are treating them as “second class citizens”. That’s what happens when you tax people to pay for something, people start assuming that it isn’t a privilege, but a right.

  2. Surely the phrase “Build it and they will come” summarises transport nicely. More roads = more cars. More cycleways = more cyclists. More public transport = more people using PT.
    I am unsure what is hard to understand about this…

    1. Or as Patrick says “What you feed, grows”, so feed nothing but more roads, get nothing but more motorists (and trucks), feed more cycleways and bus lanes, get more cyclists and PT users.

      A no brainer it should be.
      So why is it now 40+ years since California gave up on building its way out of the “traffic” problem with more roads that we are still not hearing the message over here?

  3. Absolutely the long term solution is privatisation of roads. When we have the technology to charge drivers easily and efficiently by the metre they use, we can re-privatise all forms of transport and let them compete.

    Due to their massive waste of land, motorways would quickly be narrowed. The land could be sold to local communities for green space, converted into rapid transit, or in some cases into shops with the motorway downgraded to an arterial.

    After all, the great railways of Europe were built by private companies perfectly able to turn a profit. It’s only when they state decided to start constructing roads in a massive way that they lost their customer base due to being undercut and needed to be nationalised.

    I hope that doesn’t seem like too much of a “fantasyland” – after all, transport has been conducted by the private sector for the bulk of human history. Only the fetish of the car ended that.

    1. There is no doubt that public, toll-free roads hurt railroads a lot because of unfair competition, but I am very suspicious of your history.

      As far as I can remember, transport infrastructure, especially roads, have been mainly a public endeavor. Roman roads were constructed by the government, not by private enterprises. Likewise, road construction and maintenance was a major part of the corvées of medieval serfs (unpaid labor days owed to their lords). Railroads were an exception, not a rule, and most likely due to the fact that they were natural monopolies. Sure, two companies could build parallel tracks, and sometimes did, but controlling what was going on a track was rather easy, and even necessary to avoid accidents, so each track was a monopoly of sorts. Furthermore, most railroad companies had to be provided with advantages by the government (land grants, exclusive rights, etc…) before they would build their tracks. 100% privately funded and built tracks did exist, but weren’t the rule but the exception from all I’ve read on the subject.

      1. Simon, there is no doubt that there has been state involvement in the construction of roads for almost as long as there has been private construction. It is false to say that public construction was the main source however. In ancient times, they main purpose of public road construction was to facilitate the movement of armies. Trade did benefit and used the roads, but that was not the purpose, and indeed trade was flourishing well before the Romans built their roads – in other words, road building does not precede trade, it is a result of trade and was driven by the merchants themselves.

        A more recent example is the US in the 18th century. Here’s a quote from an essay on Forbes:

        “Capital for road building was raised more efficiently by the private sector. The pioneering business seems to have been the Philadelphia and Lancaster Turnpike Corporation, chartered in 1792. For the first third of the 19th century, hundreds of private turnpike companies built thousands of miles of roads that linked western territories with the eastern seaboard. By 1821, 84 turnpike companies were incorporated in Pennsylvania, and 278 were incorporated in New York. Long distance roads were beyond the capability of any company, so work was divided among many companies that built connected roadways.”

        It is an extremely common misconception that roads are solely driven by force (taxation). Private companies and communities have banded together throughout history to voluntarily construct roads.

          1. 1. I never said they weren’t.

            2. Wikipedia on Roman roads:

            “The beauty and grandeur of the roads might tempt us to believe that any Roman citizen could use them for free, but this was not the case. Tolls abounded, especially at bridges. Often they were collected at the city gate. Freight costs were made heavier still by import and export taxes. These were only the charges for using the roads. Costs of services on the journey went up from there.

            Financing road building was a Roman government responsibility. Maintenance, however, was generally left to the province. The officials tasked with fund-raising were the curatores viarum, similar to a supervisor who manages and administers. They had a number of methods available to them. Private citizens with an interest in the road could be asked to contribute to its repair. High officials might distribute largesse to be used for roads. Censors, who were in charge of public morals and public works, were expected to fund repairs suâ pecuniâ (with their own money). Beyond those means, taxes were required.”

          2. quite user pays…
            I wonder what the BCR of a Roman road was, and what discount rate they used, being that they are still used to day.

    2. That libertarian “fantasyland” is not only unobtainable, it’s downright pernicious, a dystopia. It’s the ultimate survival of the richest with no consideration of public benefit. As Simon points out, roads have from the very beginning been considered public goods. You were free to follow the first guy’s camel. Tolls were invented early, yes (plank roads, canals, etc.), but only because they provided a distinct advantage over current routes. Thus we have to pay to ride or ship on trains, for example, but that by no means implies that they are “private”, also as Simon point out. Furthermore, privatisation has proven over and over again to be a false promise.

      1. Steve, I would consider Auckland’s current transport network “pernicious”. The area of the city with the most community severance due to state motorway construction is one of the poorest – Manukau. What’s more, the state seems to maintain the roads around the central suburbs to a much higher standard than in South Auckland!

        It is a fact that competition drives prices down – just look at the tech industry. Healthy competition in transport would also drive prices down. Just like we see a 10% difference in petrol prices between Epsom and Otara, private tram, bus, train or road companies would adust their prices accordingly. Let the southern line compete with the southern motorway on price, speed and efficiency and see who wins!

        What’s more, private road ownership encourages good urban design – if I’m the Newmarket Businesses Association and own Broadway and the surrounding streets, I have an incentive to make the road as people friendly as possible. As this blog has pointed out time and again, shared spaces and other urban design improvements, even removing parking, lead to massive increases in turnover.

        1. No that is a terrible idea. Transport is one of the few things where competition doesn’t work – the other majors ones being education and health. That is because none of these things can be properly assessed on a purely economic basis.

          In all the places in the world where transport, health and education work the best for everyone there is a complete lack of education.

          Just as examples, Finland with education, France with healthcare and the Netherlands with transport.

          The US spends many times the amount of money the Scandinavian countries do on health, with much worse outcomes.

          There is no real world evidence that competition in these three areas produces better results.

          1. “No that is a terrible idea. Transport is one of the few things where competition doesn’t work – the other majors ones being education and health. That is because none of these things can be properly assessed on a purely economic basis.”

            Not an argument, of course transport can has been assessed on a purely economic basis. Private companies built infrastructure and operated PT before the state road worhsippers came in and undercut everything. Your ignorance of history is not an argument.

            “In all the places in the world where transport, health and education work the best for everyone there is a complete lack of education.”

            “Just as examples, Finland with education, France with healthcare and the Netherlands with transport.”

            “The US spends many times the amount of money the Scandinavian countries do on health, with much worse outcomes.”

            Agreed, however how this is relevant I do not know. US healthcare is hardly a model of free competition.

            “There is no real world evidence that competition in these three areas produces better results.”

            I said competition reduces prices, which you haven’t refuted. Again, competition in transport has existed for a long time, and lead to the construction of a little thing called the London Underground, which has barely been expanded since the state entered the field of transport. When one talks about quality transport infrastructure in London, they aren’t talking about the roads. They’re talking about an extensive high quality network which was built by the private sector, undercut by the state, and has been left to rot for a century as a result.

          2. Well done you picked up on a typo: “In all the places in the world where transport, health and education work the best for everyone there is a complete lack of COMPETITION.”
            “Your ignorance of history is not an argument.” – Are ad hominem attacks really necessary? I could tell you exactly why that is a particularly silly thing to say about me but that would only lead to me attacking you.

            ““Just as examples, Finland with education, France with healthcare and the Netherlands with transport.”
            ???” – But just putting three question marks is an argument? Finland is ranked as having the best education system, France the best health system and I would say the Netherlands has the best transport system (but I admit that is a cycling biased opinion). “US healthcare is hardly a model of free competition.” – so what is? Most neoliberals seem to want to steer is in the US direction on health.
            Yes, transport was originally built by private means. As were many other things. But now we are at a different stage in our societies and those models will no longer work. That is why privatisation of transport in the 20th century was such a disaster while places that left transport nationalised continued to move ahead.

            This is illustrated well by the UK. Their national train system was always a disaster because of privatisation. And prices certainly did not fall in Britain when the national rail was privatised. It was horrendously unaffordable compared to Continental rail systems in the 1990s.The London tube was left to languish because of anti-PT neolib policies. Now that there is some semblance of sanity on this, there are huge resources being put into improving the tube system by the Crossrail project.

            As far as I am concerned you haven’t proved anything. Just regurgitated neolib twaddle.

          3. No, ad hominem is not necessary, I apologise.

            Let’s distill this down. My three main points were:

            1. The state has not provided equitable transport solutions in Auckland.
            2. True competition drives prices down.
            3. Private road ownership provides an incentive for good urban design.

            You didn’t really refute any of that, just changed the subject. You’ve started talking about education, you’ve supposed my position on education, you’ve put me in a box called “neoliberal”. As soon as you made up in your mind that I fit this (clearly hated) description, you’ve gone on a huge tangent.

            So let’s calm the hysteria and get back to the issues. Transport is a complex topic that has had a mixture of public and private solutions throughout human history.

            Private firms cannot compete with the state; they do not control a guaranteed proportion of everyone’s income. Saying that the privatisation of rail in GB failed is therefore a red herring; the industry must be totally private or totally nationalised. We have seen that mixtures do not work. Roads and rail are in direct competition with each other, just like buses and trains in Auckland.

            Going back to my very original post, I put forward the view that once technology exists where we can charge road users by the metre, we have an opening to realistic privatisation. This does not mean that roads must be privatised, indeed the state could retain ownership of roads and rail, and fairly charge between them in order to stop incentivising driving.

            On a side note, healthcare in the US could not IMO be much worse. Medicare seems to be quite literally funneling as much money as possible into the hands of the pharmaceutical companies by providing direct incentives for doctors to prescribe more expensive drugs.

          4. I have obviously completely misunderstood what you were saying. I agree with this statement:
            “indeed the state could retain ownership of roads and rail, and fairly charge between them in order to stop incentivising driving.”

            I think roads are ripe for price charging. What I thought you were saying is that all transport infrastructure and services should be privatised. I think that is a massive mistake for public transport (and was proved to be in Auckland and the UK) – not for roads which are inherently private in their nature – or rather should be if it wasn’t for the massive public subsidies that currently support them.

            Same for cycling infrastructure – but only if driving is also not subsidised.

            The only reason I raised education and health is that I consider public transport to be in the same category of services that should only be supplied by the state free of competition.

            Carry on. 🙂

          5. One comment about privatising roads or any other transport right of way is that the only efficient way to buy the land is to use the States power of compulsory purchase, otherwise what happens is you get some hold out who charges a fortune for the land under the last few percent of the route.

            Like it or not transport ROWs are always sanctioned by the State. There always will be an element of Communist shipyard to transport planning!

          6. I also like AI’s suggestion: “indeed the state could retain ownership of roads and rail, and fairly charge between them in order to stop incentivising driving.”

            That would be interesting: a HOP transponder on every road vehicle (including bikes) charging variable (peak/off-peak) rates per usage (meter and/or minute).

            (I suggested this to a transport planner in Melbourne when I was living there in 2001 and I thought I’d had a brainwave about it, but she quickly dismissed it by saying “we can’t pick winners and losers” which I didn’t understand, since I thought I was suggesting the exact opposite: a level playing field. Oh well.)

            However, the transport system/network as a whole should be complementary, not competitive. It doesn’t seem to make any sense for buses on Great South Road to be competing for passengers with trains on the Southern Line.

    3. Actually, I believe that motorways are probably very profitable based on the fuel tax raised by large numbers of cars traveling (and idling) on them. It is the low use roads that do not cover their costs (of course motorways would not work if there was not a wide network of low use roads).

      Privatising motorways is unlikely to have any new owner close or reduce them. In fact such owners may well have peak/congestion toll/charges them to optimise their usage (slow, congested peak-hour motorways move fewer cars than free flow motorways) which would benefit the city.

      1. Except when the direct money from excise duty and RUCs runs out and the government has to start dipping into general taxation to pay for big motorway projects (like the RoNS).

        Don’t you think the owners of all the failed tolled motorways in Australia and the US would have liked to have narrowed the motorways to cut their costs?

        That was really the only option as raising the tolls would only have reduced the traffic numbers even more. Or give it back to the state who then uses public money to further subsidise the shortfall and prop up an uneconomic system.

      2. Motorways are not profitable thanks to the gas tax, far from it. They are extremely expensive to build and rebuild (once their life expectancy is reached), so overall in the world, private toll-funded highways tend to charge the equivalent of 10 to 25 cents (US) per km traveled in order to recoup their costs. How much do they “make” with the gas tax? Well, presuming a relatively inefficient large sedan which consumes 8 L/100km on a motorway, here is what they are paying in different countries:

        In the US, the average gas tax is 50 cents per gallon, or around 13 cents per L. So that’s around 1 cent per km.
        In Canada, federal and provincial gas taxes are around 30 cents per L, so that’s 2,4 cents per km.
        In New Zealand, the fuel tax is about 50 cents per L, so that’s 4 cents per km, but 1 NZ $ = 0,80 US $, so that’s 3,2 cents US per km.

        In all these cases, the gas tax pays for at most about 30% of the cost of the motorway. The reality is that road funding tends to be a lot of passing of the buck…

        Local streets are mainly paid by cities and developers, either through property taxes or development fees. Yet people who drive on them still pay gas taxes on them.
        All the revenues of gas taxes and other vehicle taxes tend to flow to national/provincial/State roads, mostly to motorways which are enormously expensive.

        The result is that driving on motorways is easily subsidized at a 70-80% rate, even if it’s drivers on local streets and roads who pay the bill, it still remains that motorway driving is highly subsidized. Note also the perverse incentive that results: the most expensive road to build and maintain is the motorway, but as fuel consumption on motorways is less than on city streets, people who use the motorway pay LESS in gas taxes to fund them per km traveled than people NOT using them. So people are incentivized to use motorways whenever possible.

      3. …(slow, congested peak-hour motorways move fewer cars than free flow motorways)… actually i remember reading here that 50km/h is the maximum flow. After that safety distance diminishes it.

        1. Yes quite right, can’t remember the exact optimal speed for throughput, but because faster speeds require greater space between vehicles, the most efficient speed is well below the 100kph that everyone, especially NZTA, demand must be able to occur on every highway at all times.

          Rational, on this issue, they ain’t.

      4. Does anyone want to take a crack at interpreting this, with regard whether roading is profitable or not? From http://www.interest.co.nz/property/72451/new-environment-minister-and-housing-minister-nick-smith-argues-rma-reform-focus-hous#comments

        “The Govt will collect $195 mln for registration fees, $1,268 mln for Road User Charges, plus $1,903 mln in Excise Tax collections. That totals $3,366 mln.
        On the other hand Vote Transport is $4,518.7 mln, and of that they are spending $3,040.1 for roading.
        Basically most of the taxes collected from motorists go into roading, within 10%.

        The data is here:
        http://www.interest.co.nz/news/69928/budget-2014-summary-all-spending-plans and
        and this is sourced from: http://www.treasury.govt.nz/budget/2014/data

        1. Is that opex too, or just capex?

          Approx 50% of non-state highway roading is funded through rates, so it’s seems the balance is already several billion short. What about RoNS?

          1. Sorry Nick R I don’t have the answers and I am too busy to find out. Is there any public spirited individual who could explain this to us?

  4. Although the Soviet analogy is not really correct

    “Because that price was often far less than what people were willing to pay for that good, comrades would rush to purchase it, forming lines around the block”

    Comrades were not queuing round the block becuase the prices were low, they were queuing becaause the supply was severely restricted and in short supply and once a product ran out for the day, that was it until the next day, or perhaps the next week or month.

    When I was in Cuba I did not see huges lines of people outside the bodega stores, simply because at that time the stores had ample stocks of ration book supplies (rice,beans etc), but I am sure that changes if things become short in supply ( and becomes well known)

    1. “Comrades were not queuing round the block becuase the prices were low, they were queuing becaause the supply was severely restricted and in short supply…”

      To an economist, those two statements are identical. In a market economy, you can respond to scarcity by raising prices. The Soviet economy failed to do that, and we fail to do that with the largest component of our transport system.

  5. If anyone doubts the validity of the induced demand concept, just look at Apple. They have made many billions of dollars from induced demand. Many of their products no one needs, but there they are.

    Two experiences from my own past:
    In the 1980s, the Bay Area (San Francisco) spent $11 billion (that was real money then) on roads, then concluded that you can’t build your way out of congestion.
    I was in a meeting with the Secretary of Transportation of the US state of Pennsylvania when he said “If I had all the money in the world I couldn’t solve our congestion problem with roads alone.”

  6. Interesting article but I cannot agree with the conclusion “Induced traffic means that building roads to keep commute times down will not work.” as the cited Induced Demand study does not fully account for the benefits road building (it does recommend congestion pricing to optimise peak road usage).

    While the article reads like the conclusion that it is a waste to keep building roads is settled, there is continued debate on the validity of this conclusion. One example is outlined in Robert Cervero’s paper “Are Induced-Travel Studies Inducing Bad Investments?” (URL:http://www.uctc.net/access/22/Access%2022%20-%2004%20-%20Induced%20Travel%20Studies.pdf). In it he concludes:

    There’s still a lot we don’t know about the induced-demand phenomena, although recent research has filled some knowledge gaps. Nonetheless, highway critics have taken fairly firm positions on the issue, using past research to shoot down any and all road proposals. To the degree past studies have been problematic, so has policy advice.


    Although I personally sympathize with the aims of many environmentalists, fighting highway projects, regardless what benefit-cost numbers say, is misguided. The problems people associate with roads—e.g., congestion and air pollution—are not the fault of road investments per se. These problems stem from the use and mispricing of roads, new and old alike. They also stem from the absence of careful land use planning and management around new interchanges and along newly expanded highways. Better road pricing and land use planning are more likely to achieve the aims of environmentalists than carte blanche bans on any and all road construction.

    One final point on induced demand (again quoting someone else who said it better than I could). “Congestion rises as a function of density. Indeed congestion IS increased density. Those who advocate denser development advocate for greater congestion across the board. Their destination is the push and shove of the Tokyo subway“. I would add to this point that a key driver of congestion is the focus on having a single dense centre of employment . . . the monolithic city = congestion.

    1. “[the] key driver of congestion is the focus on having a single dense centre of employment . . . the monolithic city = congestion.”
      This is only the case with the mentality that having a car and driving a car to work/shop/recreation is a necessity.
      The current trend in the US and Europe is that fewer and fewer youths get their drivers license and buy a car, instead using the bicycle and/or public transport. If this trend continues one can argue that the congestion will come on the bicycle ways and/or bus, train. Not on the ‘normal’ roads.

    2. ‘Congestion rises as a function of density. Indeed congestion IS increased density. Those who advocate denser development advocate for greater congestion across the board. Their destination is the push and shove of the Tokyo subway“. I would add to this point that a key driver of congestion is the focus on having a single dense centre of employment . . . the monolithic city = congestion.’

      Not really. Density doesn’t create congestion, in fact, by making other modes of transport viable, density reduces congestion. I’ve seen too often NIMBYs cry about possible “congestion” if TOD was allowed to be built around train stations, not seeming to understand that if people aren’t allowed to live there, they will live in sprawl instead, and will have to drive across their neighborhood to get to their jobs, rather than take a train to it. Low-density areas create congestion as people are much more likely to drive if they live there than in high-density areas.

      There is a theory that a polycentric city would result in less congestion by having people converge at different points in a region. That seems an attractive idea, and it certainly may be somewhat true. The old streetcar lines that had the downtown area (one job center) at one end, industrial areas at the other (another job center at the periphery of inhabited areas) and residential areas on the middle of the line seems to have been using a similar concept. But the big problem here is that polycentric cities lead to increased commuting distance. The center is the area closest to every other area of the region, if you put a job center in another location, then the average distance to that center is greater than the distance to the traditional downtown. This leads to another issue, people who live farther have to take more roads and high-speed roads to get there, the result is that interchanges allowing people to go from one highway to another become packed and congestion starts occurring there rather than in the CBD.

      If you look at traffic congestion data on Google Maps for Atlanta, sprawlville per excellence, you will see that congestion occurs not so much in the old downtown, but at highway interchanges in the “first ring” of highways. Atlanta is one of the most congested American cities. So if sprawl could solve congestion by spreading job centers around the region, it would work there, but it doesn’t.

      As to Tokyo, sure, trains are congested, but Tokyo is a 37-million megalopolis. That is works at all is a marvel. Many sprawl cities with one tenth of its population are seeing their own growth choked by congestion.

      1. Tokyo is a hilarious example for a sprawlist like Tony to try to use: the great achievement of postwar Japan is that despite their very high population they have been able to keep 80% of the landmass of their islands in wilderness or productive farmland, this of course can only be done with the good urban form of higher density. To be in favour of more sprawl and urban dispersal means you hate the countryside as you are arguing for ever more of it to be paved!

        Highly dispersed cities are not only the most expensive to service with all amenities, including roads, water, waste water, electricity, street lighting, schools, policing, emergency services, basically everything, but are also cause the highest costs through externalities like health outcomes [more obesity, more traffic accidents, more air pollution] but also are much more destructive to the natural environment.

    3. So despite all evidence to the contrary – both research based and empirical (like Auckland built nothing but roads between 1950 and 2000 without any congestion relief) – you refuse to believe that the approach that accords most closely with your viewpoint of neoliberal economics is wrong?

    4. I didn’t say that it was a waste to build all new roads. There is often a good case to build _specific_ roads to solve specific problems – I mentioned the VPT, for example.

      However, building roads as a _strategy_ for reducing congestion flies in the face of all the empirical evidence. It ignores the basics of supply and demand!

      Furthermore, outcomes for recent toll roads – Clem7 in Brisbane, Route K in Tauranga, etc – strongly suggest that new roads cannot pay for themselves. It’s no surprise that these roads failed and had to be bailed out at taxpayer expense – people simply don’t value incremental road expansions enough to pay for them.

      1. Yet what is really interesting now is that while individual widenings and extensions will induce traffic we are seeing the fairly new phenomenon of total VKT in Auckland only grow at the rate of population. In other words traffic demand is in fact static and this is despite many multiple billions that have been and are still being spent in order to make driving quicker, more attractive, with more and more high quality roadspace.

        Meantime we are seeing Transit uptake, despite only getting fractions of the investment of highways are [and even less in the next funding period], grow at double the population rate. So what this would suggest is that we have reached peak road amenity, more road is simply not valued enough to find more ‘buyers’ if you like. The marginal cost adding ever more lavish urban highway and arterial roads has all but zero reward. All the demand growth is away from the driving space.

        Interestingly this relative drop in demand comes in a period that Auckland has increased it’s density, the centre has strongly revived, so clearly Auckland this century itself offers a direct rebuttal of the idea that higher density equals more congestion.

        Density here: http://greaterakl.wpengine.com/2014/10/15/mapping-population-changes-and-youngish-adults/

        Transit demand increase here: http://greaterakl.wpengine.com/2014/10/13/the-great-auckland-transit-revival-theory-and-practice

        Driving stats here: http://greaterakl.wpengine.com/2014/09/05/aucklanders-are-driving-less/

    5. Yes Tony, dense habitation and great rail transit make Tokyo’s subways and trains ‘congested’ at times but they are so successful that the streets function well for other users and uses, especially considering the numbers of people and level of economic activity.

      What causes TRAFFIC congestion to deepen and worsen in cities is auto-dependency [little option but to drive] and dispersal of habitation and employment: The reverse of higher density [closer travel destinations] and provision of alternatives to everyone driving [the option to avoid congestion altogether].

      Dispersal makes all trips longer, and not just to the centre which of course weakens under this model, but especially across town to and from all these dispersed places. And auto-dependency forces more people to drive for more trips at more times. It not only exacerbates congestion but forces everyone to take part in it.

      For a local example look at CHCH, especially now after the quakes as an increase in dispersal has been chosen for the urban form of the rebuild. This means and will continue to mean more driving, and therefore more congestion, especially as significant investment in alternatives has been rejected too. And we can see the results, absurd levels of congestion for such a small city on a flat plain. And you can not ‘blame’ the centrew for this, as there isn’t one. What was the centre is has been reduced to a through route for all the driving now required from one edge to the other.

      After all traffic congestion is simply too much driving; and nothing makes for more driving like dispersal of amenity and no options to get anywhere outside of a car.

      1. I suppose this is the key point of transport – if you build it they will come.

        Trains will become “congested” but that congestion means close proximity of humans rather than slower travel speeds.

        If you live in a city, choose your form of congestion. Mine personally would be a cycleway.

      2. Patrick if Christchurch had the amount of money per capita that has been spent in Auckland or Wellington we would not have congestion/slow travel times. Also if the residential rebuild had occurred on affordable farmland compulsory acquired with dedicated public transport/cycling ROWs or alternatively if the UGB had been temporarily/permanently dropped then redzoners and new residents would not have been pushed out to cheaper but distant satellite towns with long commutes.

        1. Brendon, please, I am not criticising Christchurch, and especially not the people there, but rather certain policy decisions taken at some remove.

          And it is instructive, what has happened there, both before but especially after the quakes, does offer a contrast to what has happened in Auckland over the same period. AKL has intensified and CHCH has dispersed. Or rather AKL has both intensified and continued some dispersal while CHCH has just dispersed.

          And this contrast does show that Tony Randle in his comments here is just flat wrong: Dispersal increases traffic congestion, intensification decreases auto dependency and increases Transit demand; or if you like in Tony’s cute rephrasing; increases train, bus, and ferry congestion. That is all I’m saying.

          And I agree that other policies in post quake were possible and desirable in CHCH, but I am not there and not sufficiently informed to make specific judgements. I’m sure you’re better placed and right about what should have been done.

          1. Fair enough Patrick. Certainly over the last seven years congestion has increased massively in Christchurch. I was out in a car today with a psychologist. She used to have a relatively short New York suburban to suburban commute seven years ago before she moved to Christchurch. She used to proudly tell her New York friends how easy it was to get around Christchurch. Now she thinks it was easier to get around New York!

            Something has gone wrong and we need some serious brain power focused on these issues.

  7. But look: it’s so obvious that building more roads reduces congestion that there is no point in even thinking about it. After all when I look out my window I can see the earth is obviously flat! I don’t need these “scientists” telling me what I can see for myself is wrong.
    I just “know” I’m right. © New Zealand National Party

  8. Very good post! I think any calls for congestion pricing in Auckland are premature. Economists love proposing policy based on theory – let’s be a little more empirical.

    There are really only 4 cities in the world that have successfully implemented congestion charging so far (though plenty of proposals have failed and there are some new proposals on the table in other places.)

    These four cities are the City of London, Stockholm, Singapore and Milan. All are very different from Auckland in a number of ways.
    1. much greater employment and residential density
    2. smaller car parking supply and higher direct charges for car parking
    3. much greater supply of high quality public transport, and correspondingly higher PT mode share
    4. generally higher petrol taxes and in some cases car ownership costs

    This is not to say Auckland should not ever consider congestion pricing, but I think it would be a big mistake not to pursue policies that would create conditions 1-4 well before congestion pricing because they are lower-hanging fruit, cheaper and easier to implement, help avoid perverse outcomes (like killing downtown or disproportionately hurting low income households, who at the moment are being pushed out to the fringe) and make congestion pricing much more politically saleable.

    A managed transition to a balanced transport system is important, and I think too many Treasury or NZCID types think road pricing alone is the answer for Auckland – or worse, a revenue stream to fund foolish new motorway projects like the AWHC!

    1. Excellent comment!

      I think you’re right to highlight the “perverse outcomes (like killing downtown or disproportionately hurting low income households, who at the moment are being pushed out to the fringe)” that could arise from congestion pricing. I’ve been taking a look into the topic, actually – the observation seems to be that congestion prices that are set to high can crowd out the agglomeration that occurs in dense, congested places.

      The US Federal Reserve Bank recently did a quite good empirical study on this subject – available online at: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2272049

    2. Julie I think there’s a couple of tensions in your arguments that should be pointed out:

      1. The fact that many cities have not implemented road pricing does not seem like a good argument against implementing road pricing. All it seems to imply is that its difficult to build political support. The same observation could be used, for example, as an argument against removing minimum parking requirements, i.e. few cities have done it therefore it should not be done.
      2. Higher costs for petrol, parking, and/or car ownership may be more regressive than road pricing. Road pricing seems most likely to affect urban commuters, whereas the other costs are less targeted and therefore hit a range of low-income households. Pricing vehicle use *tends* to be less regressive than pricing vehicle ownership.

      But completely agree that road pricing is not a priority compared to some other policy changes.

      1. “All it seems to imply is that its difficult to build political support.”

        In other news, economists continue to be unhappy that the public is not rational enough to try out their theories.

        1. try this: “marijuana law reform campaigners are unhappy the public is not liberal enough to support their reforms.”

          The difficulties involved in making change is not unique to proposals for economic reform. It’s common to almost anything that matters: bus lanes, education, taxation …

      2. P.s. Also where road prices were set at a level that maximised flow (as Peter argues) then they would be likely to support more efficient land use outcomes, i.e. higher employment/residential density, than what would be achieved otherwise.

    3. Yes, excellent comment, and observation.
      Certainly conditions 1-3 should be pursued (not sure about 4, as Stu and Kelvin point out, in the absence of 3, 4 could be more regressive than road pricing).

      I wonder what the true, quadruple bottom-line (economic, social, environmental, cultural) cost of driving cars and trucks on roads is, taking into account the health costs, nuisance of traffic (loss of amenity) to the neighbourhood, etc.

      I wonder whether it would be fairer, and on the multiple bases above, cheaper, to provide the best public transport system/network (including freight/goods delivery) practically possible and make it free to use (at point of use), and charge the non-PT-users who continue to use the roads to pay for the PT (and the roads).

  9. Well we still need to give people freedom of choice and some alternatives.
    We should not totally remove all but one option.
    For example if some new developments has no road but just a bus operator. The bus operator will have a monopoly and will charge whatever he wants.
    Same thing if we only have tollroad but no bus or train. We will be ripped off by the toll roads.

  10. The statement that reducing road capacity has no noticeable effect on congestion is incorrect. About 15 years ago the London School of Economics did a ground breaking study of situations around the world where key road links had been severed (e.g. by an earthquake taking out a bridge or elevated highway). Although this is not common, they found about 70 examples (from memory) where nature had performed this experiment for us – no researcher would ever get permission to close an important road for several years to see what happened. Although there was some variability the researches found a remarkable thing: – although most of the traffic was displaced onto other routes around the blockage (increasing traffic on parallel routes and detours), a significant proportion, averaging about 25% simply went away. In other words, some journeys were no longer made. This 25% was the induced traffic effect – journeys that people previously made because were convenient were no longer made when travel times became too long.

    1. Citation please? Sounds like an interesting study.

      Also: “no researcher would ever get permission to close an important road for several years to see what happened”

      A number of cities have intentionally demolished urban freeways in recent years. They’ve found few measurable effects on road congestion following the teardowns. Robert Cervero’s 2007 study of freeway teardowns found that: “freeway-to-boulevard conversions, a form of urban re-prioritization that gives more emphasis to neighborhood quality and less to automobility, have yielded net positive benefits without seriously sacrificing transportation performance. ”

      Paper here: http://www.uctc.net/papers/836.pdf

  11. LA, always gets the mention as the bad poster-child, however personally have never had trouble in LA traffic even in peak it is generally moving and the freeway metering and carpool lanes do their jobs. Sure all the highways are ugly, but once cars are ‘selfdrive’ these freeways will be a significant asset.
    Indeed some of the GPS data suggests NZ traffic can be worst when you consider excess travel time.

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