Primal and Dual Access

Recently published

Accessibility, measuring the ease of reaching potential destinations, is increasingly being considered as an effective indicator to evaluate the performance of transport and land use interactions. Primal accessibility, a generalization of the first accessibility formulation proposed by Hansen, has been widely used in many studies and demonstrated to be a reliable tool for project, program, and policy evaluation. The dual of accessibility, measuring the time required to reach a given number of opportunities, is less often considered but can be used for optimization in location covering‐type problems. This article, hence, clarifies the definitions of primal and dual access, and applies both measures to the Minneapolis—St. Paul metropolitan area for auto and transit to demonstrate their practicality as a metropolitan‐level measurement. We explore the correlations and differences between the primal and dual access to better understand the relative strengths of the measures. It is found that, as with primal accessibility, dual accessibility is an efficient approach to evaluate accessibility, which is straightforward to calculate and to explain to policy‐makers and the public.

Dual accessibility to jobs by auto (travel time in minutes).
Dual accessibility to jobs by auto (travel time in minutes).

The State of Transport Education

I will be speaking at a Transport Australia Society panel on “The State of Transport Education” to be held August 8, 18:00 – 19:30 at ACRWORLD Level 13, 6-10 O’Connell Street Sydney. Registration in advance required. Register here.

Please join the Transport Australia Society for a panel discussion on “The State of Transport Education” with Dr. Kasun Wijayaratna of UTS and Professor David Levinson of USYD and understand from their professional views how we can be prepared for the upcoming changes successfully in Australia.

As we see unprecedented growth in the transport sector currently in NSW with infrastructure projects and a rapid emergence of new transport technologies, the transport education sector is key to enabling the future vision of transport.

A crucial discussion not to be missed.

This discussion will cover the current state of education, the pace of changes in the industry and how well we are equipped to tackle the challenges of an expanding and changing transport future including the introduction of smart systems.

Light refreshments will be provided prior to the presentation.

Some Observations of China (2019)

I visited China recently to attend the COTA CICTP conference in Nanjing sponsored by Southeast University and pre-conference in Beijing, sponsored by Beijing University of Technology. The hosts were excellent, and if you get the chance to attend a Chinese conference, it’s worth doing. 

A view in Nanjing
A view in Nanjing

China is not a developing country any more than Australia or the US is. Certainly there is an unevenness in the distribution of wealth, as there are in many countries (Indian Reservation vs. San Francisco, Northern Territories vs. Sydney). As we write in The Transportation Experience, All counties are developed, all countries are developing)

Although there are gradations, it’s useful to speak of three types of nations: developed, developing, and undeveloped (following the maturity, growth, and birthing stages). From a transportation perspective all nations are developed nations. That seems to counter ordinary experience in undeveloped and developing nations where service isn’t of high quality or everywhere available. In what sense could this be true?

The Transportation Experience: Second Edition
The Transportation Experience: Second Edition

The modern transportation systems were birthed in the “developed” world environment, energized development through companion innovation processes, and were deployed as development pushed and pulled deployment. At that time, they were deployed in the undeveloped world. They were pushed and pulled by the same processes. For example, there were early railroads in Africa and South America where development opportunities called for them. The difference between the developed and the underdeveloped nations is that the undeveloped nations experienced western-style development at the fringe, so to speak. The companion innovations that bloomed as modern transportation was created and deployed fit the western situation very well. They took hold only in limited ways in other places.

The economic development programs that emphasize deployment of the systems successful in the developed nations in the undeveloped nations don’t much make sense. Wilfred Owen argues equity as a basis for subsidized deployment. It isn’t fair and just for the undeveloped nations not to have good highway and other services. That argument has merit. After all, their deployment has already been tried with limited success. What’s needed is the development of services suited to the situations in the undeveloped nations.

On the other hand, one could rightly view all nations as undeveloped in a transportation sense. That follows from observing that modern systems are not so modern. They were developed using once-modern tools to fit once-current circumstances, and they are obsolete today.

Throughout urbanized China, major streets are too wide, and too much of that space is given over for cars. This is a classic problem of elite decision making, viewing the world from the windshield of their own vehicle, rather than the needs of the majority who are not driving. On a per square meter per person logic, the allocation of space is much worse.

The Metros are too crowded. There are not enough lines. The frequency is excellent, but they just need more. While spatial coverage is good in Beijing, it could be better in Nanjing. But of course if you are adding lines, rather than services the best way to do that is to improve spatial coverage.

Despite hosting the Olympics in Beijing (and the Youth Olympics, which is a thing, in Nanjing), China is still not ready for non-Chinese speaking tourists without guides. We did it, but getting tickets for things like the Forbidden City was not at all obvious (and had to be done online, no English instructions at the site were worth anything). Similarly at other tourist sites, the instructions were poor, though the rest of the sites took Yuan at the site, with annoyance. The tickets for the high-speed train didn’t have English on them except for station names, so we could figure it out, but it was not obvious. The numbers were in Arabic, fortunately.

China is generally more technologically advanced in payment than the US (though not Australia), and is all Alipay or Wechat pay, with QR codes. This includes toll booths, the taxi driver took a photo of a screen with a QR code with his camera to pay . They were inconvenienced by cash, and don’t like western credit cards. They did not take Apple Pay.

Everyone is attached to their smartphones, even more than in Australia or the US. The opportunity for a good augmented reality glasses which display text, and use eye movement as the user interface, is amazing. So people can see what is in front of them through the text, but still connect to their social networks or whatever it is people do.

Security is everywhere, every tourist site, every transit station. Cameras are ubiquitous, taking pictures of every car’s license plate every block on major roads. You are being tracked. People seem very used to this. It is the future because of the security ratchet. Again from The Transportation Experience:

The politics of security are difficult. If you are in favor of security, you must be in favor of more spending on security, or on anything that will “keep us safe.” If politicians or bureaucrats oppose a proposed security measure, and something happens they will be blamed, … . Security ratchets up quickly. Ratcheting down can only really be by attrition.

VPN and WiFi weren’t very good (the great firewall killed most things I’d want to see). Roaming with an Australian phone carrier (Vodaphone) worked fine and gave good internet. It was worth $5AU/day for roaming (though this implies $150/month for internet service, which is on the steep side).

It's not raining, but the umbrellas are everywhere.
It’s not raining, but the umbrellas are everywhere.

Finally, what’s up with the Umbrella people? It’s summer and dry and many of the ladies (and a few of the gentlemen) are walking around with umbrellas, presumably to protect their skin from the harmful rays of the sun (Beijing is 40 degrees north, almost as far north as Minneapolis (45 degrees), where this is rare, even on the sunniest days of summer). First, humans evolved with those ‘harmful rays’, so shielding from them may be unhealthy. Second, the pollution in Beijing and Nanjing surely provides another layer of insulation. Third, as a westerner, I tend to agree with our collective norm, that at least to a point, people look better tanned than pale. (But not orange.) Fourth, the tour guides need umbrellas as identifiers, if everyone uses umbrellas, this identification role weakens. And fifth, from a social space argument, the pokes in the face from other people’s umbrellas seem not only impolite, but what should be a violation of norms.

1953 Detroit Metropolitan Area Traffic Study – Data Discovered …

Jeffrey Lin calls my  attention to recovered microdata from the 1953 Detroit Metropolitan Area Traffic Study, available here:

He re-discovered these data at the UCLA data archive and asked the UCLA library to post it to Dataverse. This is one of the first travel surveys, led by Douglas Carroll himself (the progenitor of the four-step transportation planning model).

In a recent working paper, “Freeway Revolts!” Lin and Jeff Brinkman use these data to estimate the “barrier effects” of urban highways.

The Metropolitan Travel Survey Archive remains a useful place for historic surveys, and newer surveys can be found at the NREL Transportation Secure Data Center.

Overestimation and underestimation of travel time on commute trips: GPS vs. self- reporting

Recently published:

  • Carrion, Carlos and David Levinson (2019) Overestimation and underestimation of travel time on commute trips: GPS vs. self- reporting. Urban Science. 3(3), 70 [doi]

The underlying structure of road networks (e.g., circuity, relative discontinuity) contributes to the travel time perception of travelers. This study considers additional factors (e.g., arrival flexibility, access to traffic information) and tests nonlinearities linking perception of travel time. These factors are linked to four categories according to time perception research in psychology: temporal relevance, temporal uncertainty, and temporal expectancies; task complexity, absorption, and attentional deployment; and affective elements. This study estimates the relationship on data collected from commuters recruited from a previous GPS-based study in the Minneapolis-St. Paul region consisting of trips from home to work and back. For these work trips, the subjects’ self-reported travel times and the subjects’ travel times measured by GPS devices were collected. The results indicate that nonlinearities are present for road network attributes. Furthermore, the additional factors (e.g., arrival flexibility, access to traffic information) influence the travel time perception of travelers.

Figure 1 Proportion of trips according to travel time of commute from GPS data and survey data: GPS vs. stated; expected vs. GPS; stated vs. expected.
Figure 1 Proportion of trips according to travel time of commute from GPS data and survey data: GPS vs. stated; expected vs. GPS; stated vs. expected.

Transport Rankings

The 2019 Shanghai university rankings are out. In the Transport Science & Technology subject, the University of Sydney is ranked #5 in the world:


  1. Beijing Jiaotong University
  2. Tsinghua University
  3. Delft University of Technology
  4. Southeast University
  5. University of Sydney
  6. Tongji University
  7. Massachusetts Institute of Technology
  8. University of British Columbia
  9. University of California Berkeley
  10. Shanghai Jiao Tong University

Our Civil Engineering program moved to 24th according to these rankings. The University did well overall. While I don’t much trust rankings, I’ll brag anyway. I am proud to be a part of this. If you too want to be a part of this, get a degree at the University of Sydney. Our new Master of Transport Program is available now …