Every weekend we dig into the archives. This post by Peter was first published in September 2015.

In July, I started taking a look at the economics of public transport fare policies. In the first part of the series, I took a look at how traffic congestion can be a rationale for public transport fare subsidies. (Parts 2 and 3 dealt with different issues.) I observed that:

In the absence of congestion pricing (and in the presence of other subsidies for driving, such as minimum parking requirements), higher public transport fares can result in a perverse outcome – additional congestion and delays for existing road drivers. This is shown in the following diagram:

PT fares and congestion diagram

Effectively, a failure to price roads efficiently means that we have to provide subsidies for public transport to prevent car commutes from being even more painful than they currently are.

But how much congestion reduction can we attribute to public transport? How much slower would car commutes be if some people weren’t travelling by PT instead of clogging up the roads? And how much is that worth to us?

It’s not possible to test this experimentally – we can’t exactly build a bunch of cities that are identical except for their PT systems and see what happens. (Transport research budgets are not nearly large enough.) However, we can observe the outcomes from various “natural experiments” that disrupt public transport systems while leaving everything else unchanged, such as natural disasters and public transport strikes.

Stu Donovan pointed me towards a recent research paper that analysed traffic speeds during public transport strikes in the Dutch city of Rotterdam. The authors, Martin Adler and Jos van Ommeren, use detailed traffic flow and speed data to model how 13 PT strikes that occurred from 2001 to 2011 affected traffic speeds. Because strikes prevent people from using PT without impeding road traffic, the outcomes observed during strikes give us some indication of what would happen to congestion in the absence of PT.

If you’re interested in knowing a bit more about the topic or the methodology, I highly recommend you read the paper. (It’s an excellent paper!) Here, I’d like to focus on a few key findings from the analysis.

First, the authors found that PT helps to speed up car journeys by reducing the number of people driving:

We demonstrate that during a citywide strike, car speed within the city decreases by about 10%. For highways, strikes exhibit a much smaller speed reduction of about 3%. During rush hours, the reduction in speed is more pronounced. These results imply that during rush hours, public transit provision reduces car travel time on inner city roads by about 0.2 minutes per kilometer travelled, whereas it reduces car travel time on highways by 0.02 minutes per kilometer. Hence, for cities such as Rotterdam, travelers on inner city roads benefit much more from public transit provision than highway travelers.

Intuitively, these results make sense. The benefits of PT for drivers are much higher in busier areas, such as Rotterdam’s inner city roads. However, Rotterdam’s ring road highways still derive some benefits.

The second interesting finding is that the popularity and ease of cycling in Rotterdam – even though it’s not exactly leading by Dutch standards – cushioned against some of the negative impacts of PT strikes:

a full-day citywide strike increases bicycle flow by 24% implying that a large share of travelers switch to bicycle use (rather than car use), which presumably reduces the car flow increase and therefore the speed reduction of a strike. Bicycle ownership and use is much higher in the Netherlands than in other countries in the world, so this result is likely specific to the Netherlands.

In other words, the availability of multiple congestion-free networks – public transport and cycling – meant that the roads didn’t have to accommodate all of the people who couldn’t get on the bus on strike days. In other words, the availability of multiple transport choices enhanced network resilience.

Third, the authors calculated the value of congestion reduction benefits attributable to public transport in Rotterdam. Based on some plausible assumptions about journey lengths and the value of time, they estimate that:

The annual public transit congestion relief benefit is then about €95 million (assuming 252 working days), so about €79 per inhabitant. This excludes any benefits of public transit provision on weekends that we assume to be negligible, so this is likely an underestimate. Given 721 million public transit passenger kilometers (OVPRO, 2014), the congestion reduction benefit per public transit kilometer is €0.13. This benefit is substantial given that the cost per public transit kilometer is €0.46.

In addition to congestion welfare losses there are rescheduling costs to car travelers. [Note: only 55% of the reduction in PT trips on strike days was balanced out by the increase in car and bicycle trips, meaning that a large share of people chose not to travel.] We do not include these costs, nor do we include the loss to public transit ticket holders or any other external cost of car driving that are likely an order of magnitude smaller than the effect through congestion.

The costs of providing public transit in Rotterdam are partially covered by subsidies, about €0.28 per public transit kilometer. So, the congestion relief benefit is about 47% of subsidies.

This is a really interesting finding! It puts a monetary figure on the congestion relief delivered by PT. (For Rotterdam, at least.) And, interestingly, it’s a large enough figure to justify a good proportion of PT fare subsidies. There are also other rationales for fare subsidies that I haven’t discussed here, such as social equity for people without cars and various types of network effects in PT provision.

But even if we leave those aside, this finding suggests that drivers should be happy to spend some fuel tax revenues to subsidise public transport.

What do you think about congestion and public transport?

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25 comments

  1. I’m not sure if the above article is right. We know induced traffic eats away the gains in travel speed of increased roading capacity, so if more people travel by bus it just opens up road capacity for more car trips to be “created”. This is an unfortunate finding of some studies I have read (but can’t put my fingers on them right now). So really the only way to reduce road congestion is congestion pricing – time of day, day of week pricing on at least all the busy roads and motorways. Note this is completely different to regional fuel taxes where if you make a car journey at peak times it cost you the same in tax as a journey in the middle of the night. And its important that people see where this congestion charge money goes – and that should be giving people alternatives to the congestion charge – i.e. using public and active transport, ability to live closer in to where you work, educate and play.

    1. The ability to ‘move where you work’ is massively curtailed when there’s an enormous housing shortage and affordability issues. Tolling penalises those who can’t afford to live where they work or work in an occupation where there’s work in the city centre.

      The deeper issue is really “how do we make housing affordable?” and then “how do stop people in inner-city suburbs with decent transport walling their area off to development?”

      1. Isn’t this where Phil Twyford’s UDA comes in. It will be able integrate all the multiple complexities of transport and housing under one organisation that can undertake projects at pace and scale.
        For my city of interest -Christchurch -such a UDA could transform housing and transport in the city within a decade or so. The economics of housing affordability could move on from ‘driving until you qualify’.
        A UDA could manage re-introducing commuter rail back into Greater Christchurch with the building of 10,000 higher density affordable housing around new train stations which will make high frequency services viable from a patronage point of view.
        A UDA could also manage implementing light rail connecting heavy rail to the city centre -first from Addington station and later from Riccarton station. Light rail could then (stage 2) run out Lincoln road and open up the south-west growth corridor for something better than auto dependent suburbia. This could add another 10,000 high density affordable houses only 20-30 minutes from the city centre.
        Residents of the 20,000 houses would be something like 50,000 people. They would provide the core patronage for a congestion free transport system that is likely to expand -providing more transport and housing benefits…
        You can read more here.
        https://medium.com/land-buildings-identity-and-values/greater-christchurchs-future-the-fat-banana-aba0402f16a4

        1. So where are we at with the UDA concept? Where are we at with the government led project at Unitec, as an example that will show the strength of the government’s steel?

          At Unitec, are they planning it all around public transport, accept that Carrington Rd has no need to be a through-route for general traffic, and decided to make it a public transport and active transport corridor, with general traffic only needing local access?

          Or will we just get more of the same?

    2. In general, if we continue with the same planning methods, you’re right that any drivers switching to other modes will be replaced by other drivers taking their place. But if we change how we do things, here are some ways to reduce congestion without other drivers taking the place of the drivers who have switched mode:

      – Lower the speeds. This has two complimentary effects – it can reduce the number of drivers who want to drive on the route, preferring other routes with faster speeds, and it encourages mode shift to walking and cycling because it makes the route more safe and pleasant.
      – Reorganise the street layout, so that ratruns are blocked. If through-traffic is removed, the only people who might “fill the space” are locals, but they are just as likely to be encouraged to walk and cycle due to the safer and more pleasant environment.
      – Reduce the road capacity in and near the area. As an obvious example of this, if 8 lanes of traffic coming into a part of the city (say, on three different roads) is reduced to 5 lanes of traffic, there will simply be less traffic in the local roads in the area.
      – Parking charged to cover the cost of the traffic it induces.
      – Cheaper public transport.

    3. shouldn’t the theory be. If PT is rapid transit -which is faster than driving at congestion times then subsidising its implementation will create a new equilibrium point between driving and PT users, based on the speed/convenience of the fastest transport mode?

  2. It seems a little strange that the article didn’t reference the local counter-factual study from 2013 – the impact on the wellington economy of the rail line being taken out: https://www.transport.govt.nz/news/multi/report-assesses-transport-disruption-of-wellington-storm/

    Building PT patronage is a long game, I think, especially if the effect is going to climb over the ‘induced demand’ challenge Peter refers to. Decent road pricing of course, could/might speed this up enough to observe the congestion relief in something like real time. That reinforces the other point, that it requires a package of measures working together.

  3. The resiliency offered by parallel networks – cycling, walking and other people-sized modes, buses, rail, driving, is a good goal.

  4. “So really the only way to reduce road congestion is congestion pricing – time of day, day of week pricing on at least all the busy roads and motorways.”

    The evidence from some places says not so. Vienna, just named the world’s most livable city for the ninth consecutive year, has managed to de-congest their streets mostly by making public transport so cheap. The mode share for car trips is currently 27% with a target of 20% by 2025. Here is the progress to 27% (The Politics of Sustainable Transport in Vienna
    by Ralph Buehler, John Pucher, Alan Altshuler
    Vienna, Austria reduced the car share of trips by a third between 1993 and 2014: from
    40% to 27%.)
    Compare this with Auckland’s target to reduce mode share,in the city only, by 20% over the next ten years from a figure of about 50%. This is an abject fail.

    The clear evidence of Vienna is that there has not been a back filling of the space created by many leaving their cars at home.

    I agree with you that congestion pricing would help, but it seems clear that almost no-one has the political appetite (guts if you prefer) for this. We have seen recently that Minister Lees-Galloway has not even allowed ACC to raise petrol prices by only 2c per litre to recover the cost of road accidents.

    AT, with their supposed statement of intent to increase public transport ridership, has shown almost no inclination to raise parking prices to encourage a move away from car usage.

    These are some of the reasons that I so strongly advocate the “Vienna Solution” as a way to de-congest our streets; reduce carbon emissions; and there is the by-product of improving financial outcomes because of cheaper transport for the less wealthy.

  5. The day that tradies catch trams (or other non-ute transport options) to work I believe will be the turning point for NZ fixing both its housing crisis and its chronic traffic congestion problems.

    Basically this will indicate when the automobile transport monopoly is broken and there are multiple congestion free modes of transport, whereby people can choose the best choice for their particular needs at the time.

    This turning point will further indicate a huge change in housing supply, with plentiful amounts of new types of housing to meet all the different types of housing demand.

    More here.
    https://medium.com/land-buildings-identity-and-values/what-if-tradies-preferred-trams-to-utes-5e29ba4988a6

    1. Yes, the concept that tradies don’t always need utes is challenging to most people, and every discussion we can start on the subject will open people’s eyes to the fact that in other places, public transport (and people-sized personal mobility devices like cargo bikes) does indeed work well for tradies. I use my cargo trailer when I’m doing local jobs, and would use it for jobs further away if there were safe cycle lanes.

      And as you said in your article on Talking Transport:

      “It would mean public transport was built first. It would mean planners and developers had master planned neighbourhoods with rapid transit in mind, before sub-dividers had sprawled into it. It would mean the type of housing, the density of housing, the way the streets are laid out is such that new neighbourhoods maximise the benefit that public transport provides… in Germany it is commonplace to see tradies heading to building sites in new subdivisions using public transport because in Germany public transport is built first.”

      It can work here. And because people establish a lifestyle based on the transport options they have available when they first start living somewhere, it’s imperative that the public transport is built first, not just when a demand has been proven.

      1. It also means build site security would need to increase so tools can be safely left on-site. At the moment I don’t blame people for lugging their gear back home at the end of each day.

        1. Yeah, that’s a good point. And security of gear is often a transport issue. For example, young sports people will sometimes drive to practice rather than cycle because there’s no security for their sports gear and for their bike, so easier to have a car, and leave any gear in the car.

        2. Yes it’s normal to bring your smaller tools to site. What about all the trades that go to site for a few hours then on to the next site like myself. I need to carry a lot of gear in the vehicle to cover all situations.Most sites are the main contractor with significant number of sub contractors.
          And to make matters worse if the site goes bust chances are you cannot retrieve your tools for some time if left on site.
          Then add in most construction sites start at 7am and other than infill in established areas with PT you need vehicle transport.
          Time is money, I have no issues driving a double cab Ute at free flowing 6.30am to site.

          1. Would be interested to know what impact changes in employment forms has had on all this. I started as a labourer and rode my bike to the bosses house where I met up with apprentices etc, we then went out to site. Nowadays I believe many are self employed or working for labour firms, not only do they have to make own way to a site but also lose out on holiday pay etc.

          2. There are so many types of trips to provide more transport options for; tradies’ utes aren’t the most obvious place to start, for the reasons Mike gives. But worthwhile to think about, none-the-less, as it does have me thinking that:

            – intensification projects in established areas can involve fewer vehicle trips because some of the construction workers would take PT – particularly if they’re there for a length of time and get used to the route they need. So it’s another way these intensification projects put less strain on our networks. Having said that, I don’t think there’s enough planning around the truck movements, which have an impact on safety in built up areas.

            – the German model Brendon mentions in his article, where all the tradies go by public transport to site because that’s the only access provided initially, is obviously possible. They must’ve solved some of these issues. Do they have more stability in their construction industry so firms going bust isn’t a realistic scenario? And they obviously have freight cars for bulky items?

          3. Mike we in the Nelson Transport Strategy Group (Nelsust) have been advocating for peak hour clearways for buses and tradies. Here in Nelson we don’t have enough population to make good enough use of the clearways by just them, so the idea is to open them up to tradies too, so you aren’t inducing extra demand from car commuters by increasing capacity for them. Crucially these bus (and tradie) clearways will make bus commuter faster than ca commuting, part of that thing of making it more attractive than car commuting.

    2. Not sure if this counts as “tradies” but there is a lot of hi-vis on public transport these days what with all the CBD construction going on at the moment

      1. bjfoeh
        I endorse your comments and certainly when I take early buses from the Shore there are many travelling to construction work. Parking $25 – bus $6.60. Economically an easy choice. That is why it is so important that AT price parking to assist in the conversion to PT use.

        I was amazed that in a reply to an OIA AT indicated that they price parking in parking buildings to enable the building to be replaced at the end of its life. Where did this concept come from? As often as I read the Parking Strategy I cannot find any reference to this. Have AT just made this up? It is little wonder that Mayor Goff has written to AT about their parking policies, albeit in political waffle talk.

        Increasing ridership to the City should be easy given that services are generally so frequent. One challenge is to make them more timely by adding bus lanes.

        1. Sending in another LGOIMA to find out where that little snippet did come from, T-i? That really sounds like somebody trying to insert some rationality to an irrational policy.

    3. Brendan what we in the Nelsust Transport Strategy Group are advocating for here is clearways for buses and tradies. So in this way you give bus riders and tradespeople relatively uncongested commutes whilst still incentivising car drivers to with ch modes but also importantly not creating inducing ed demand for car commuting. What do other people think – would clearways for buses and tradies work in provincial centres where we really haven’t got many buses?

    1. Meanwhile there is no WiFi at Akoranga busway station. I phoned AT to ask whether it had failed and was told it had never been provided there. Seems strange, as Smales Farm and Albany both work.

    2. bjfoeh
      Let’s hope Akl – Hamilton rail works this time around. A high speed train would probably make it more likely to succeed in the way that rail works in Europe.

      I have proposed that as part of a move to carbon zero that the carbon component of local air fares should be paid by air travellers and that this amount should be applied to supporting carbon friendly alternatives. Obviously this is not diesel trains. Perhaps a carbon zero network is possible at least to the high population areas starting with the golden triangle?

      1. I would have thought a Waikato commuter line – Hamilton Central to Pokeno – would have attracted many more riders than the Hamilton-Auckland line.

        I would have started with that and then looked at extensions north and east (Tauranga) afterwards

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