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Transport - general

Mar 2, 2016

Managing excessive car use: what's the low hanging fruit?

A study of urban form in the US concludes that increasing the density of population and employment is a slow way to significantly reduce car use compared to directly pricing driving

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Traffic congestion, USA
Traffic congestion, USA

In a new paper, Urban form and driving: Evidence from US cities, Gilles Duranton of the Wharton School and Mathew A Turner of Browns University find it is “more costly to manipulate driving behaviour through densification policies than through congestion pricing or gasoline taxes”.

Professor Duranton and Professor Turner wrote the influential 2011 paper, The fundamental law of traffic congestion: evidence from US cities; they concluded that “both road capacity expansions and extensions to public transit are not appropriate policies with which to combat traffic congestion”.

In their new paper, they map data from the US National Household Travel Survey on a national one square kilometre grid describing urban form, population density, demographics and sectoral employment.

Our estimates of the relationship of driving to urban form allow us to assess the cost effectiveness of densification as a policy response to excessive driving. These estimates suggest that urban form is not cost effective compared to explicit pricing programs.

In particular, even concentrating the population residing in 83% of the area of the continental US into an area of about 1,500 square kilometers would result in only about a 5% decrease in aggregate driving, and this policy appears to describe the upper envelope of what densification policies can accomplish.

On the other hand, existing estimates of the gasoline price elasticity of driving suggest that a similar decrease in driving would be accomplished with a gas tax that is no larger than gasoline price fluctuations observed over the past five to ten years. Congestion pricing programs appear to have even larger effects.

They also consider a more modest policy that illustrates the likely limits of density as a tool of policy. They find that if 1% of US population and employment were moved from the area inhabited by the fifth population decile of density to the ninth decile, aggregate driving would decrease by less than 1%.

Higher density is desirable for other reasons like lifestyle and productivity, they say, but it isn’t a cost-effective way to reduce car use in the US.

While the US isn’t Australia, the implications of this argument are similar to the points I made recently about the limited pay-off in mode share from investing in mega public transport projects in Australian cities (see Will simply building more public transport seriously suppress car use?).

There are good reasons to promote higher densities in established areas as well as increase investment in public transport, but their combined impact on car use in a car-oriented country like Australia is likely to be modest and protracted. They’re not enough.

Managing the negative impacts of driving – like congestion, pollution, emissions and reduced street amenity – can be addressed more speedily, efficiently and effectively by pricing, taxing and regulatory measures. They might be poison fruit in political terms but they’re the low-hanging fruit in policy terms.

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14 comments

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14 thoughts on “Managing excessive car use: what’s the low hanging fruit?

  1. drsmithy

    Pricing signals to discourage peak time/direction travel and encourage alternatives should be explored.

    The vast majority of people have little choice about when and where they travel in peak times, and the people with the least amount of choice are usually the ones with the least capacity to pay. “Pricing signals” are as pointlessly discriminatory there as they are in healthcare.

  2. Waffler

    Dylan #10

    It is amazing that we spend a fortune building infrastructure to support jobs in the city but the developers and businesses that directly benefit from this pay so little.

    While MM will do much more than allow 28,000 new CBD jobs, these jobs are a major justification for the investment. Yet the Gov’t seems to be ruling out charging inner-city businesses for it. Road pricing is one aspect, parking charges are another and so is land and development taxes. We need them all to both help shape desirable development and operational outcomes and to help fund needed infrastructure.

    After all, new businesses in the greenfields pay developer contributions that make setting up a business closer to where people live more expensive. Yet they would contribute nothing to locate in the CBD.

    And Oz #9 is spot on – we have spare capacity outside of peak hours. We also have lots of spare capacity in the counter peak direction. Pricing signals to discourage peak time/direction travel and encourage alternatives should be explored. And of course, on roads at least, there is lots we can do to squeeze more out of the system.

    However, we need to remember that travel demand will eventually grow to fill the available capacity, so we will never “solve” the problem.

  3. Dylan Nicholson

    Markus, I very much doubt price is the main reason people avoid public transport. Though I am wondering what outcomes have been observed from the free tram zone trial.
    I don’t mind too much that inner city dwellers who only need to make short trips subsidize those who need to travel longer distances, but you’d think that myki would make distance-based pricing easy enough to introduce. At any rate, PT is very affordable here, especially inter-city PT. I’d almost rather have it more expensive to better pay for itself and to encourage existing PT users to use more active forms of transport (cycling especially).

  4. Markus

    I’m all for congestion pricing–especially if the raised revenue would go toward reducing the price of public transport.
    I also would like to see more zones. Living about 4K from Melb CBD and in front of 2 tram lines, I’m always amazed that I pay the same amount taking public transport there as someone from Frankston or Sunbury. On weekends, my wife and I pay less for driving and parking in the CBD than taking the tram.

  5. Dylan Nicholson

    Surely $11B to allow for an extra 28,000 jobs in the CBD can’t be right, that’s nearly $400K per job. If those jobs are generating on average $40K per year in taxes they’d collectively take 10 years to pay for themselves. I’d have thought if they occurred in other parts of the city they’d generate just as much revenue and that $11B could be put towards infrastructure that would benefit everyone. Do we really need/want to have that many more jobs in the CBD?

  6. Oz (Horst) Kayak

    One definition of congestion is “when having to wait for more than one traffic light change before moving or crossing an intersection or location.”
    Observation of many of the serious and irritating congestion points in the Melbourne metropolis indicates that most of the time 24/7/365 they are uncongested.
    The congestion is dramatically reduced “off-peak” and even in many locations during school and public holidays. At many locations, only a reduction of 20% in demand to handle traffic will allow the system to operate at a tolerable level.
    Differential road and parking pricing can reduce the demand in peak periods more effectively compared to what exists today. System wide “ramp metering” that prevents entry onto roads before leaving the kerbside, garage or commercial car park is another possible option to stop vehicles entering the road system when the network is unstable and being forced to try to operate at above its short term capacity.
    There is existing excessive capacity in the road system, but not between 7and 9 am on a weekday.
    There may not be spare capacity in many parts of the road network at 11 am on many Saturdays either, but that time is in general private time and the congestion inconvenience requires a different model.

  7. Socrates

    I would agree demand needs to be managed. Stockholm does it pretty well with road pricing. But the most effective lever costs nothing – limiting parking. In fact, taxing parking is a tidy revenue raiser.

  8. Dylan Nicholson

    Then I’m definitely far from convinced it’s a good use of $11B+ taxpayer’s money, much as I support in general the idea of improving PT around the inner city area, but only if it’s part of an overall plan to reduce automobile dominance/dependency.

  9. Alan Davies

    Dylan Nicholson #5:

    The main outcome of not doing it is the extra 28,000 jobs MM permits in the CBD would locate instead in the suburbs, mainly the inner city and some suburban centres. The effective ceiling on CBD capacity means it would become even more specialised in finance and govt, as firms with less need for a CBD location would decentralise.

  10. Dylan Nicholson

    I’d agree, that doesn’t sound does like a reasonable use of public funds at all.
    But what’s the estimated business cost of *not* building it? How do they expect people would travel instead?

  11. Alan Davies

    Dylan Nicholson #3:

    Define “reasonable”!

    Well, the Melbourne Metro bus case says construction of the line will reduce cars’ share of motorised AM peak period travel in metropolitan Melbourne by around half of one percentage point. That’s for an outlay of $11 Billion. That doesn’t sound like a reasonable pay-off if changing mode share is the objective. The main benefit of spending big on urban public transport projects is better transit, not lower car use.

  12. Dylan Nicholson

    Define “reasonable”!
    But for a start, ensuring that all future road building/improvements are done in such a way that it is not car-drivers who get automatic priority. I.e., if part of a road needs work, what can be done to ensure it’s pleasant and safe for walking, cycling, and attractive to businesses that could offer services customers currently have to travel far for. If there is public transport on or near the road, look at what can be done to make it easier to get to, and for it to move more efficiently. In some cases that will inevitably mean removing amenities that are there now only because motorists have been the primary focus of nearly all urban planning for the last 50 years or so. We’ve spent decades paving our cities for cars, despite everything we know about the downsides of encouraging excessive car usage, so a little re-appropriation of public space seems well overdue.

  13. Alan Davies

    Dylan Nicholson #1:

    Many European cities already have large areas with high densities and a very high standard of public transport. Moreover, they’ve used a range of policies for decades that make driving less attractive e.g. petrol taxes, rego, limits on parking.

    Absent higher taxes/charges and stronger regulations, how else can travellers be induced to drive less on a significant scale, at reasonable cost to the public and within a reasonable time frame?

  14. Dylan Nicholson

    http://inrix.com/scorecard/

    Just looking at traffic congestion, there’s no question that European cities/towns in general manage it far far better than any US city. Yet very few have the sorts of road pricing you seem to be considering. It seems a bit defeatist to assume we can’t effect the sort of necessary cultural change to encourage people out of their cars without resorting to making driving cost more (which will make no difference to those on high incomes, for a start).

    But I have to say, having observed traffic in all those European countries (other than Luxembourg), it’s genuinely shocking that Italy has the lowest hours spent in traffic, as Italy unquestionably had the worst traffic congestion I’ve ever experienced anywhere.

    I’m curious where Japanese cities would rate on there too (I was amazed how little traffic there was in downtown Tokyo at peak hour considering how many people live there, but apparently the average speed of driving in Tokyo is a whole 16k/h so who knows…)

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