Polycentricity Podcast

Following up on our article in The Conversation on Polycentricity, I was interviewed on 2SER (107.3) radio (June 13, 7:30 pm) about polycentrism. Here is the podcast: https://2ser.com/three-cbds-in-one-city/


One CBD… how about 3? Sydney is becoming polycentric. The original CBD remains an ideal place for some businesses, but for others, it is impossible expensive or too far away. David Levinson a Professor of Transport and Engineering at the University of Sydney believes it is a requirement for any growing city to create a structure which suits the businesses.

William Gleeson spoke to him for this report.

Some comments on Hyperloop

I have some comments on the so-called Hyperloop on p. 10 of the current issue of Modus.  There are comments by others as well.


Hyperloop is not a reality, and may never be 

Hyperloop can’t be a solution to any current transport problem, as it doesn’t exist. This is like the Wright brothers pitching airports before they’d flown an aeroplane – it’s a bit premature. Magnetic levitation technology has been around for years and we’ve had pneumatic tubes since the 18oos. Putting these two technologies together doesn’t work at this time. There’s no reason public agencies should propose to build lines until they’ve built a test track that functions.

Long tubes of metal are going to expand and contract. You can imagine shorter tubes connected by rubber or something, but what ‘s the loss of vacuum? We don’t know. Nobody’s built one. Since they’ve never put a person in a hyperloop, they have no idea how people are going to react. In addition to not having technology, they don’t have a business case. How do they get passenger flows that justify the cost? This isn’t faster than anything that has come before – we have aeroplanes. They haven’t come up with a market where this works better than anything we already have.

— David Levinson is professor of transport at the University of Sydney


Friends of Erskineville: Conversation with David Levinson

I am honoured to be invited to present to the Friends of Erskineville (Facebook signup) group on Tuesday, 11 June 2019 from 19:30-20:30, at the Erskineville Town Hall Committee Room talking about a bunch of things, notably station access.

Friends of Erskineville's photo.

David hails from the USA but since 2017 has been a professor of transport engineering at Sydney University. His area of expertise is travel behaviour and transport planning. Recently he founded the Walk Sydney group and has written numerous articles about how we can improve walkability in Sydney. He has analysed the design of a number of intersections in the Erskineville neighbourhood and suggested ways to improve them. In a recent article he wrote about the possibility of improving station access, such as by creating a southern entrance to Erskineville station.

David will give a presentation on these issues followed by an informal Q&A.

See the following links for some of David’s recent articles:

Update June 13, 2019

The recording is up on Facebook in two parts:

On ideas

There are two kinds of ideas.* There are ideas that other people should do and there are ideas you do yourself.

Everyone has lots of ideas for other people. Advice is nearly free; it’s easy to spend other people’s time and money. It’s even easier to spend the public’s.

Ideas for yourself have a more rigorous filter. What can I do? Well, I can easily write a blog post. But as they say, talk is cheap.

I might think the US should explore Mars, but unless I am a multi-billionaire,** there is not a lot I can do on my own to push that forward. Even if I were, or donated to the Mars Society, I am still not the astronaut or engineer or mechanic or factory worker who makes it all possible.

But idea generation should not be all “put up or shut up”. I still might have a useful idea for you (I am convinced I do, as a professor of ideas and doctor of philosophy, when asked what I do, I say “I profess”), that is better than the idea you have for yourself.

I do have a useful idea for you,  you should definitely discount other people’s ideas about how to spend your time and efforts, only you can prioritize for yourself.


* There are two kinds of people, those who divide the world into two kinds of people and those who don’t.

** Or as Howard Schultz would say, person with multiple billions of dollars.

Master of Transport at the University of Sydney

Develop your critical understanding about the engineering, urban planning, and business management of transport. Understand the prevalence and identification of transport systems and core capabilities for analysing and designing them.

Our Master of Transport is Australia’s first interdisciplinary degree, focusing on the engineering, urban planning, and business management of transport.

This professional full-time degree is ideal for graduates wanting to pursue a career in the global transport sector or professionals already in the field wanting to upskill.

It is designed to further your ability for strategic and logical reasoning, deduction, network and temporal data analysis, and expand your proficiencies in broad interdisciplinary analysis.

Our Master of Transport is truly multidisciplinary, allowing professionals the opportunity to undertake a unique combination of units spanning engineering, architecture and business throughout their studies.

It also leverages the strengths of the Institute of Transport and Logistics Studies, which has exceptionally strong links with industry and is recognised by the Australian Government as a centre of excellence in research and education, and the ongoing transport engineering research being undertaken by the Faculty of Engineering.

Candidates for the Master of Transport complete 72 credit points, consisting of:

  • 48 credit points of core units
  • 18 credit points of electives
  • a 6 credit point capstone unit

Find out more about the study plan for this degree.

This program can also be taken as a:

The Master of Transport will commence in Semester 1, 2020.

More details.

To apply, visit here:

Transportist: June 2019

Welcome to the June 2019 issue of The Transportist, especially to our new readers.  As always you can follow along at the  transportist.org or on Twitter.

designing the 30-minute city

I briefly made an incursion upon the USA, and gave the 12th Annual Wachs Lecture, designing the 30-minute city, available on YouTube. (Note: There are some sound issues for the first few minutes, but those get resolved quickly.)

The Conversation

Transportist (the blog)


Transport Findings


Papers by Us

by Others


  • Survey for Uber Pick-up Times (A PhD student is trying to determine the actual distribution of schedule delay for Uber pickups, you can help expand human knowledge by sharing your data. It will not be used for nefarious purposes.)

Revived Open Access Journals



Safety in Numbers for Bicyclists at Urban Intersections

Recently published:

  • Carlson, Kristin, Murphy, Brendan, Owen, Andrew, Ermagun, Alireza, and Levinson, D. (2019) Safety in Numbers for Bicyclists at Urban Intersections Transportation Research Record. [doi]

Abstract: This study assesses the estimated crashes per bicyclist and per vehicle as a function of bicyclist and vehicle traffic and tests whether greater traffic reduces the per-vehicle crash rate, a phenomenon referred to as “safety in numbers” (SIN). We present a framework for comprehensive bicyclist risk assessment modeling, using estimated bicyclist flow per intersection, observed vehicle flow, and crash records. Testing a two-part model of crashes, we reveal that both the average of annual average daily traffic (AADT) over a 14-year period and the estimated daily bicyclist traffic (DBT) have a diminishing return to scale in crashes. This accentuates the positive role of SIN. Higher volumes of vehicles and cyclists lowers not only the probability of crashes, but the number of crashes as well. Measuring the elasticity of the variables, it is found that a 1% increase in the average of AADT across the time window increases the probability of crashes by 0.14% and the number of crashes by 0.80%. However, a 1% increase in the estimated DBT increases the probability of crashes by 0.09% and the number of crashes by 0.50%.

Sydney Metro Opening Day: A Review

Sydney opened the long-awaited first Northwest section of its “Metro” line. Sydney has long had grade-separated, high-frequency train service (Sydney Trains) through its core, the “Metro” is different in that it is:

  • single-deck rather than double deck, with more doors, for faster boarding times
  • standing rather than sitting oriented (on a crowded train more standees than seated passengers, compared with Trains)
  • automated rather than manually driven
  • with platform-based as well as train-based doors, to improve safety.

In other words, while Sydney Trains is what Americans would think of as commuter rail, but on steroids, Sydney Metro  is like late 20th century (early 21st century) trains built in much of the developed world, most similar to systems like BART, DC Metro, or MARTA.

To get to the Metro, we took Sydney Trains from Redfern to Epping. At Epping, one descends and descends to reach the Metro platform. The stations and controls from Epping to Chatswood were remodeled from the early 21st century trains line (when the corridor was expected to be a Trains rather than a Metro. We took the line west to Tallawong (a parking lot and near the train stabling facility), and alighted and boarded the eastbound train which we took to Rouse Hill, where we alighted for lunch, making a series of culinary choice errors at the Rouse Hill food court, though I am not clear one could do otherwise.

The good news is that demand was high (75,000 in five hours, the Sydney Morning Herald gushes), apparently exceeding expectations. People are curious about the line, want to see it succeed, want to be able to use public transport to reach the city. Even before the problems that I will soon describe emerged, it was Standing Room Only on the westbound run.

The trains had indicators showing where they were on the line. There was an emergency stop button located near the doors which look like a User Interface disaster waiting to happen (that is, there will be an enormous number of false positives as people will push the button accidentally or in the believe it is required to open the door, as in an elevator).

The braking sound of the train is very much like DC Metro, though deceleration did not induce the same kind of nausea that DC Metro does. There is nevertheless a significant uncomfortable jerk as the Metro train comes to a stop at many of the stops.

After thoroughly exploring the Rouse Hill Town Centre, we queued up to board the Metro back, to go to Chatswood, and then transfer to a Train back to Redfern.

The bad news is the service operator (MTR) was not quite ready to provide a reliable service. We may eventually discover whether someone(s) specifically screwed up, or whether failure is indeed an orphan. Apparently (I did not witness this, but people report) there were issues with platform and train doors aligning, and issues with doors closing properly and with trains overshooting the platform. This held up trains Chatswood and Macquarie Park, and thus eventually all the trains in the line, as shockwave of stoppage cascades backwards all the way to Tallawong.

It took 1 hour and 40 minutes from Rouse Hill to Chatswood. The first 40 minutes were queueing at Rouse Hill, so as not to overload the platform for the few trains making it through, it was no 90 second, or 4 minute, or 5 minute headway as variously promised by various people at various times. The remaining hour was on train from Rouse Hill to Chatswood. The scheduled time is 35 minutes station-to-station.

Epping Metro, as the train to Tallawong approaches
Epping Metro, as the train to Tallawong approaches
No up escalators at the spacious Rouse Hill Metro Station
No up escalators at the spacious Rouse Hill Metro Station












This opening debacle will, as first impressions are important, likely create a perception that the service is unreliable. If this is coupled with a few well-publicised rush hour breakdowns, it will take years to fully regain a reputation for reliability, and people will clamor for restoration of more express bus services. Obviously some of this technology problem is teething issues, and will be eventually sorted out, but surely this should have been worked out in testing … unless it was rushed for some reason.

The queue management was professional if indicative of problems. The communications with customers about the problems was vague.

Now, to be fair, opening day often brings about unexpected outcomes.

The opening of the Green Line light rail between Minneapolis and St. Paul was marked by an automobile wrongly driving on, and getting stuck on, tracks; and the train hit multiple pedestrians in its first year.

The Opening of the Liverpool and Manchester railway killed a prominent Member of Parliament. So the delays on the Sydney Metro are perhaps small potatoes in the scheme of things. One just would have hoped for a better performance.

* I am not commenting on the strategic decisions about the location of the line, etc. here.


How close is Sydney to the vision of creating three 30-minute cities?

This article, by Somwrita Sarkar, Hao Wu, and David Levinson first appeared in The Conversation.

The Greater Sydney Commission has proposed a 40-year vision of a metropolitan region formed of three “cities”: the Eastern “Harbour” City, the Central “River” City, and the Western “Parkland” City. The plan aims to create 30-minute cities, where the community has access to jobs and services in three largely self-contained but connected regions. Thus, Sydney would be polycentric.

The Greater Sydney Commission’s Three Cities Plan. Greater Sydney Commission

A polycentric city has multiple centres of employment, economic or social activity. Local labour markets and residential zones minimise long commutes, create a sense of place and neighbourhood, and strengthen economic agglomeration as companies, services and industries benefit from being close to one another.

However, it is still unclear whether Sydney is actually moving towards such a structure. In our recent work, we developed new ways of measuring polycentricity. We applied these to Journey to Work data from the 2016 Census to test how consistent the current centricity patterns of Greater Sydney are with the proposed plan.

How do you measure polycentricity?

Traditionally, employment densities are used as a measure of polycentricity. If the density of jobs in a location is higher than the average density for the entire region, then it is a centre.

However, this simple measure misses a key notion that makes cities what they are: network flows and spatial interactions. People “flow” from one place to another. Employment centres “attract” flows, and residential areas “produce” flows. Thus, a city is a collection of locations that interact dynamically, connected by daily commuting flows.

We proposed a set of new metrics to capture this idea of flows. We defined the net inflow of people to a location as the total number coming to this location to work minus the total number going from this location to work elsewhere. If the net inflows are positive, this place is a centre.

The chart below illustrates the idea. The base arc on the circle shows the number of people “flowing” out of a location to another location. The connecting arcs are coloured black if the net inflows into the focus regions (a), (b) or (c) are positive.

Testing polycentricity via net inflows: (a) Sydney City and Inner South (Sydney CBD), (b) Parramatta, (c) Eastern Suburbs. Source: The authors

Sydney CBD clearly emerges as a global centre for the whole region. Parramatta is a regional centre. Other locations such as the Eastern Suburbs are not centres at all.

The net inflow to a location can be divided by the total number of trips in the system, so inflow values are scaled from 0 to 1 using a standard statistical procedure. The higher the value, the higher the centre’s rank in the urban system. Here, a score of 1 means the centre is an absolute: all the trips in the system are a net inflow into the centre.

This gives us a trip-based centricity measure. And based on the area of the location, we can calculate a density-based centricity measure.

The maps below show trip-and-density-based measures – (a) and (b) respectively – for Greater Sydney at the Statistical Area Level 2 (representing a community that interacts together socially and economically).

Note the dominant role of the Sydney CBD. The other centres emerge as weak centres. Also, many of the second-order centres are very close to the CBD.

Visualising polycentricity in Sydney (red indicates highest values): (a) trip-based centricity, (b) density-based centricity, (c) transit-accessibility-based centricity, and (d) auto-accessibility-based centricity. Source: The Authors

The concept of accessibility

Counting the net inflow into a location may provide us with information about general centricity. However, it still does not tell us how easy or difficult it is for people to actually get to jobs. This brings us to the idea of accessibility.

Walter Hansen defined accessibility as “the spatial distribution of activities about a point, adjusted for the ability and the desire of people … to overcome spatial separation”. More practically speaking, a location is accessible if it can be reached within a set time (say 30 minutes) from another location.

We counted the net accessibility of a location by counting the number of jobs minus the number of workers (labour) that could be accessed from a particular location (SA2) in Sydney within 30 minutes. We counted travel time both by car and by public transport during a usual weekday peak hour (Wednesday 8am). Similar to the trip and density measures, accessibility centricities can also be scaled as values between 0 and 1. This allows us to compare across the four measures.

In the maps above, (c) and (d) show the transit and auto-based accessibility centricities based on accessibility for public transport and vehicles. Sydney CBD is highly accessible. The second-order centres show much weaker accessibility.

Takeaways for urban policy and the three-cities plan

The chart below shows the top-ranked centre, Sydney CBD (Level 1 centre), and the lower-ranked subcentres (Levels 2 and 3) emerging from our analysis.

Identified Level 1, 2, and 3 Centres for the Greater Sydney metropolitan region. Source: Authors

Accessibility planning should guide the design of a polycentric city

The design of polycentric Sydney should be guided by accessibility, the locations of jobs and homes, and subregional labour market organisation.

In short, the region should give priority to making jobs accessible by locating new jobs in emerging centres, instead of a mobility-focused system that takes people to jobs.

Reduce spatial mismatches between jobs and homes

Our results show that Sydney, paradoxically, remains strongly monocentric and strongly dispersed at the same time. The Sydney CBD accounts for 15% of jobs in the region, with the remaining 85% of jobs scattered around in weaker second-order centres and non-centres. Positive correlations exist between percentage of employed workers, trip-based centricity and the subcentre ranks.

But we see significant disparities between these ranks and accessibility centricities. This shows the spatial mismatches for commute lengths in the system.

A subcentre with high trip-centricity, employing a high percentage of workers, but relatively lower auto- and transit-based accessibility centricity, implies that even though a significant percentage of the population comes to this location to work, access to jobs at this centre within 30 minutes is low.

A policy response would be to increase the accessibility of jobs from this location, as it already serves as a centre. This situation is particularly clear in the cases of Parramatta-Rosehill and Macquarie Park-Marsfield. Penrith and Liverpool too have extremely weak accessibility centricity.

Parramatta CBD is emerging as a secondary centre in the Greater Sydney region, but with much weaker accessibility of jobs than Sydney CBD.haireena/Shutterstock


Polycentric cities should promote spatial justice

As cities grow in size, commute lengths increase if the labour market for the entire metropolitan region is integrated. Commute lengths will stabilise if a city has a clear polycentric or modular structure.

In the case of Sydney, spatial equity has always been a concern. However, inter-city comparisons show city size has a strong bearing on its equity and efficiency.

Our results show it’s increasingly important for larger cities to introduce a framework of subregional labour markets as part of the polycentricity agenda. Enabling shorter commutes for workers will improve spatial equity as well as efficiencies.


The article is based on this paper: Sarkar, Somwrita, Wu, Hao and Levinson, D. (2019) Measuring polycentricity via network flows, spatial interaction, and percolationUrban Studies. [doi])

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