Accessibility Analysis of Risk Severity

Recently published:

Accessibility loss by time threshold when highlighted link is removed.
Accessibility loss by time threshold when highlighted link is removed.

Abstract:

Risk severity in transportation network analysis is defined as the effects of a link or network failure on the whole system. Change accessibility (reduction in the number of jobs which can be reached) is used as an integrated indicator to reflect the severity of a link outage. The changes of accessibility before-and-after the removing of a freeway segment from the network represent its risk severity. The analysis in the Minneapolis – St. Paul (Twin Cities) region show that links near downtown Minneapolis have relative higher risk severity than those in rural area. The geographical distribution of links with the highest risk severity displays the property that these links tend to be near or at the intersection of freeways. Risk severity of these links based on the accessibility to jobs and to workers at different time thresholds and during different dayparts are also analyzed in the paper. The research finds that network structure measures: betweenness, straightness and closeness, help explain the severity of loss due to network outage.

Keywords: Accessibility, Vulnerability, Network structure, Betweenness 

On Greater Sydney’s 40-Year Plan

On a Sunday (yes a Sunday, now that is odd) the Greater Sydney Commission and Transport for NSW both released draft 40 year plans:

Since I am under contract to neither organization, I am free to give a review of the documents. I have comments prepared on the idea of the Three-City plan (dislike) and have something in the hopper on the 30-minute city (like), but am not clear whether it realisable.

The Draft Greater Sydney Region Plan is a gorgeous document, it is well-laid out, and pleasing to read. The Transport for NSW plan is much draftier, and appears to have been rushed. On the assumption that this is not staff’s fault, but rather that it was grabbed from their reluctant hands by political higher-ups who wanted a joint release, and who correctly assume that no one (i.e. only internationally-originating transport planning professors) actually reads plans, I will not pick on them for their unreadiness. The Sunday release is perhaps a tell in this regard.

My first blush comments about some remaining aspects of the Greater Sydney Region 40-year Plan are below (with the caveats that I have read the document once, have not read the previous documents, and am new to the country).

It is great to see the coordination between the agencies, and at least the idea that the transport and land use planning should be in sync.

The plan writes “Importantly, infrastructure will be sequenced to support growth and delivered concurrently with new homes and jobs.” This is good planning practice, and it is important that timing as well as end-state is considered.  Whether this is well-executed remains another matter. As they say, time will tell.

In general, most of the GSC plans seems reasonable and hard to disagree with, if somewhat vague in many cases. For instance. “Strategy 8.1 consider cultural diversity in strategic planning and engagement.” OK, I’ve considered it, now what should I do with it?

It is a 40-year plan (Well a “40-year vision and 20-year plan”). Infrastructure lasts a long time, we want to make sure we take sound, long-term decisions. Now I like the future and all, and even think visioning is a good idea, as is preserving options, but 40 years is a long time, even in something as slow moving as transport networks.

The Chronologically-Aware might note that it is already 2017, not 2016, and it is a 40 year plan for 2056. Let us not be bound by petty calendars, this is planning time. Also since it is already 2017, and it won’t be adopted for at least some time, it might wind up being a 38-year plan.

Think back to 1976, it was before the internet or mobile telephony (or even wireless phones), before widespread Cable TV or the VCR, before Personal Computers even (it was the year Apple was founded). How much of a 1976 plan’s prediction of life today would be correct?

I’d suggest very little of the difference between 1976 and the present would have been accurately estimated by most people, or even most planners, or futurists, in 1976. Certainly we imagine that road projects that were funded in 1976 were realised soon thereafter. And much hasn’t changed.

To borrow from Sting (1983, i.e. 34 years ago): People still face a

rush hour hell

packed like lemmings in shiny metal boxes,

contestants in a suicidal race,

‘… shouting above the din of  their Rice Krispies,’ living their lives of quiet desperation. Other aspects are far different. Far fewer factories ‘belch filth into the sky’ as least in the developed countries. Far fewer workplaces are ‘hindered by  picket lines,’ as the power of labour has withered. Far fewer businessmen have their own secretaries. We don’t have flying cars. We do have 280 characters.

Still, plans (or visions) can shape growth patterns, even if the forecasts of life are terribly inaccurate. Plans I am most familiar with, the New Town Plan of Columbia, Maryland (where I grew up) and the Wedges and Corridors plan of Montgomery County (where I worked for 5 years) both gave form to, and continue to shape their communities. Columbia was expected to be completed (built out with 100,000 residents) within 15 years (in fact, it was closer to 35 years, and the Town Center area still is not finished, 50 years on).

The Interstate Highway System of course was an important shaper of development patterns across the US, and enabled the rise of just-in-time production, among other things. It was expected to be done in 16 years (1972, from 1956), but wasn’t really essentially done until 1982, and officially done a decade later.

Laying a street network, like the Manhattan Grid,  is a largely irreversible process, as evidenced by the lack of change in the street grid even after catastrophic events like the London fire or San Francisco Earthquake.

The expectation of the plan is that Greater Sydney grows to 8 million over 40 years. Demographics are among the easiest things to forecast for long time periods, as people age and migrate slowly. At current rates, I don’t doubt the estimate of 8 million. This however depends on an open immigration policy, which I am not sure traditional Australia will continue to support.

I don’t see any discussion of an intercity High-Speed Rail or Very Fast Train. Yet clearly the transport agencies are considering this and making provision for it. Certainly the notion of HSR remains vague, and the details missing, but this is a 40-year plan.

Aspects of funding made me happy to read, even if they were hedged:

  1. “explore and, where appropriate, trial opportunities to share value created by the planning process and infrastructure investment (such as rail) to assist funding infrastructure” … Land Value Capture ! p. 31
  2. “investigate the potential of further user charging to support infrastructure delivery” … Road Pricing ! (though “charging” users  only shows up on 3 pages) p.31
Movement and Places Framework. Source: TfNSW and GSC
Movement and Places Framework. Source: TfNSW and GSC

The technological tsunami about to hit surface transport is acknowledged, but not dealt with. The word “autonomous” (as in Autonomous vehicles) shows up on 5 pages. Not enough thought is given to this, given the timeframe.

The Movement and Place framework (p. 39) is good, and highly reminiscent of the Hierarchy of Roads. I like the more detailed and nuanced design from Transport for London better, (TfL’s 9 cells vs.  GSC/TfNSW’s 4), but there is an argument for simplicity.

On education, the document says: “The NSW Government will spend $4.2 billion over the next four years on school buildings, which it estimates will create 32,000 more

Streets types matrix from Transport for London looking at tradeoff of Movement and Place. http://content.tfl.gov.uk/street-types-matrix.pdf
Streets types matrix from Transport for London looking at tradeoff of Movement and Place. http://content.tfl.gov.uk/street-types-matrix.pdf

student places and 1,500 new classrooms.”

This is $131,250 per student! This is $2.8M per classroom. This seems a lot, even for Sydney. (p. 40) I sure hope some of this maintenance, not just capacity expansion.

The term “Accessibility” shows up on 14 pages. This is good, and the word seems to be used correctly. This is consistent with the idea of the 30-minute city.

Under “Directions for Sustainability” (p. 122) It is great they are using metrics. I take issue with some of them …

“An efficient city
Metric: Number of precincts with low carbon initiatives

A resilient city
Metric: Number of local government areas undertaking resilience planning”

Honestly, these specific ones are terrible metrics. Particularly the first one. Just measure (or estimate) the carbon emissions, not the number of “initiatives”.  Compare with the tree canopy “Metric: Proportional increase in Greater Sydney covered by urban tree canopy”, which looks at the actual amount of tree coverage. Resilience is admittedly trickier to assess.

 

Constructing a plan is hard (in a political sense of finding something that enough people will agree to that is more than pablum, writing down a coherent set of strong ideas is actually not that difficult at this stage in history, with so many go ideas to draw from). I applaud the effort, and think it is better than the alternative. But it could be better still, and that is the reason for discussion and comment.

Access to jobs by transit increases in many U.S. metros

From the Press Release

Bus interior

Top increases in job accessibility by transit
1. Cincinnati (+ 11.23%)
2. Charlotte (+ 11.02%)
3. Orlando (+ 10.83%)
4. Seattle (+ 10.80%)
5. Providence (+ 10.65%)
6. Phoenix (+ 7.51%)
7. Riverside (+ 6.59%)
8. Milwaukee (+ 6.53%)
9. Hartford (+ 6.44%)
10. New Orleans (+ 6.18%)

Top 10 metro areas for job accessibility by transit
1. New York
2. San Francisco
3. Chicago
4. Washington
5. Los Angeles
6. Boston
7. Philadelphia
8. Seattle
9. San Jose
10. Denver

Annually updated research from the Accessibility Observatory at the University of Minnesota ranks 49 of the 50 largest (by population) metropolitan areas in the United States for connecting workers with jobs via transit.

The new rankings, part of the Access Across America national pooled-fund study that began in 2013, focus on accessibility, a measure that examines both land use and transportation systems. Accessibility measures how many destinations, such as jobs, can be reached in a given time.

Though rankings of the top 10 metro areas for job accessibility by transit remain unchanged from the previous year, new data comparing changes within each of the 49 largest U.S. metros over one year helped researchers identify the places with the greatest increases in access to jobs by transit. Cincinnati and Charlotte improved more than 11 percent. Seattle, which ranks 8th for job accessibility by transit, improved nearly 11 percent. In all, 36 of the 49 largest metros showed increases in job accessibility by transit.

“This new data makes it possible to see the change from year to year in how well a metro area is facilitating access to jobs by transit,” said Andrew Owen, director of the Observatory. “Transit is an essential transportation service for many Americans, and we directly compare the accessibility performance of America’s largest metropolitan areas.”

This year’s report—Access Across America: Transit 2016—presents detailed accessibility values for each of the 49 metropolitan areas, as well as detailed block-level color maps that illustrate the spatial patterns of accessibility within each area.

Key factors affecting the rankings for any metro area include the number of jobs available and where they are located, the availability of transit service, and population size, density, and location. Better coordination of transit service with the location of jobs and housing will improve job accessibility by transit.

The findings have a range of uses and implications. State departments of transportation, metropolitan planning organizations, and transit agencies can apply the evaluations to performance goals related to congestion, reliability, and sustainability. In addition, detailed accessibility evaluation can help in selecting between project alternatives and prioritizing investments.

The research is sponsored by the National Accessibility Evaluation Pooled-Fund Study, a multi-year effort led by the Minnesota Department of Transportation and supported by partners including the Federal Highway Administration and 11 additional state DOTs.

The Accessibility Observatory at the University of Minnesota is the nation’s leading resource for the research and application of accessibility-based transportation system evaluation. The Observatory is a program of the Center for Transportation Studies. CTS is a national leader in fostering innovation in transportation.

 

The Transit 2016 report and other Access Across America research reports for auto, walking, and soon biking, are available at access.umn.edu.

Detailed interactive color maps illustrating the jobs accessible by transit in each metro area are available on the study web page at Access Across America: Transit 2016.

Metropolitan Transport and Land Use – Planning for Place and Plexus

Now available for pre-order, with a shipping date in December if all goes well: Metropolitan Transport and Land Use.

Metropolitan Transport and Land Use: Planning for Place and Plexus, by David M. Levinson and Kevin J. Krizek.
Metropolitan Transport and Land Use: Planning for Place and Plexus, by David M. Levinson and Kevin J. Krizek.

As cities across the globe respond to rapid technological changes and political pressures, coordinated transport and land use planning is targeted as a solution and is the subject of increased interest.

Metropolitan Transport and Land Use, the second edition of Planning for Place and Plexus, provides unique and updated perspectives on metropolitan transport networks and land use planning, challenging current planning strategies, offering frameworks to understand and evaluate policy, and suggesting alternative solutions.

The book includes current and cutting edge theory, findings, and recommendations which are cleverly illustrated throughout using international examples. This revised work continues to serve as a valuable resource for students, researchers, practitioners, and policy advisors working across transport, land use, and planning.

ISBN-13: 978-1138924260

ISBN-10:1138924261

About the Author

David M. Levinson is Professor of Transport Engineering at the University of Sydney School of Civil Engineering. From 1999-2016 he taught and served as Chair of Transportation at the University of Minnesota, where this book was first crafted. He serves as the editor of the Journal of Transport and Land Use and is the author or editor of a dozen books.

Kevin J. Krizek is Professor and Director in the Program in Environmental Design at the University of Colorado Boulder. He recently served as a Visiting Professor of ‘Cycling in Changing Urban Regions’ in the Institute of Management Research at Radboud University (the Netherlands).

Spontaneous Access: Reflexions on Designing Cities and Transport – Now in print

Spontaneous Access: Reflexions on Designing Cities and Transport is now available as a high-quality color trade paperbackIt is also available in hardcover.

It remains available as an eBook on Kindle Editions  and at the iBookstore. If you have the option, I encourage you to get it on Apple’s iBooks, where it has additional features, like pop-up references and image galleries, as it was designed in ePub3.

Spontaneous Cover-Front

Table of Contents

  1. The City Spontaneous
  2. The 60-Year Line
  3. Community without dendricity
  4. The pint-of-milk test
  5. The timeless way of building networks
  6. Axioms about roads
  7. Garden streets
  8. Vitality
  9. An archipelago of walkability
  10. Filling in
  11. Leapin’ frogs
  12. The reorganization of road function
  13. Beyond the plan view
  14. Interfaces of freedom
  15. Instruments of control
  16. Shared space
  17. Winter is coming
  18. Diversity as insurance
  19. Differentiate city and country
  20. Don’t confuse the place for the time
  21. Great Britain doesn’t have an Americans with Disabilities Act
  22. Designs serve varied and sometimes conflicting interests
  23. A vision of visions
  24. A faster horse
  25. The Ant and the Grasshopper
  26. Deconstructing Busytown
  27. Spontaneity in a can, spontaneity in a plan
  28. Building the city spontaneous
  29. Framing regional development
  30. First do no harm

There are several themes in the book:

Cities and their networks operate on multiple timescales simultaneously. Traffic lights change by the second, rights-of-way last millennia. Cities see massive daily flows of people in and out. The core, timeless, enduring elements contrast with the faddish ephemera that too much effort is focused on. The future is emerging, but determining what we are looking forward to will be enduring or ephemeral should be the critical focus of anyone involved with transport and city design.

This book does not shy away from the normative and prescriptive. In this it differs from much academic work, including my own, which tends to the positive and descriptive. Principles are laid out, which I believe to be true and correct, many of which are not scientific in the way they are framed. They of course may lead to testable hypotheses, but they are also value-based.

The idea of the ‘spontaneous city,’ one that serves needs and wants in real-time, is a theme running through both the title and the text. What conditions encourage people to take advantage of their city (and therefore make it stronger)? What conditions worsen life for the users of the city?

The emergence of new transport technologies gives us a chance to restore and correct, to right what is wrong with the places we live. From the railroad and electric streetcar creating separation between places where people lived and where they worked, to the elevator enabling high rise construction, to the motorcar which put suburbanization into over- drive, all significant transport innovations reshape cities. The new autonomous vehicle, the new electric vehicle, the new shared vehicle, the vehicle form, shape, and size are a transformation of similar scale and scope. These changes will create opportunities over the coming decades, which we can seize or reject.

This book is about how cities do work, how cities can work, and how cities should work. In part it is about traditional fields of planning and engineering, but takes a much broader concept of design principles than those fields usually do. This is because it is also about evolution and it is about opportunism. The world is changing fast. We can make it a more humane place than it has ever been, or we can allow it to devolve into a more brutish environment, where we remain a victim of our collectively built environments, rather than their master.

When the book speaks of ‘cities’ it really means the entire metropolitan ‘urban system,’ not just the historic core city (or the central business district). Downtown is but a part of the city, and the central city in many metropolises is not even a plurality of residents.

Much of this book includes complaint, and it may feel like shouting into the wind. But every complaint is about a design failure, either with intention or by accident, that degrades experience for everyone, or degrades the experience of some for the benefit of others. Life is comprised of tradeoffs, but not all tradeoffs are made at the appropriate rate of exchange. Both cities and their transport networks are the product of thoughtful human actions and unconscious emergent processes, where systematic behavior drives the underlying logic of designs.

The optimal design of transport networks to serve the goal of spontaneous access cannot be determined in the absence of knowledge about the actual development pattern. The optimal development pattern cannot be known without regards to the plan of the network. Discovering the right combinations of networks, land use, and other urban features is what makes cities successful. The measure of their success is their population, their wealth, their happiness.

But even more importantly, the optimal transport network for the technology of one era is not necessarily the optimal network of the future, and the same is true for development.


Much of Spontaneous Access is drawn from my blog transportist.org, or streets.mn, although it has been significantly edited and reorganized from posts that may have appeared there. In that sense, it is a younger sibling to the recent (2015) book The End of Traffic and the Future of Transport with Kevin Krizek. It is a collection of reflexions (a somewhat archaic British way of spelling “reflections”), short essays that collectively give insight into today’s design problems and some possible solutions.

A model of two-destination choice in trip chains with GPS data

Recently published:

Studying trip chaining behavior has been a challenging endeavor which requires the support of microscopic travel data. New insights into trip chaining can be gained from real-time GPS travel data. This research introduces a framework that considers two-des- tination choice in the context of home-based trip chains. We propose and empirically compare three alternatives of building choice sets where we consider various relation- ships of the two destinations (such as major–minor destinations, selecting one first, and selecting two concurrently). Our choice set formation alternatives use survival models to determine the selection probability of a destination. Our results reveal that trip chaining behavior is shaped by the features of retail clusters, spatial patterns of clusters, trans- portation networks, and the axis of travel. This research reveals that not only the spatial relationship but also the land use relationship of the destinations in a trip chain affect the decision making process.

Justice, Exclusion, and Equity: An Analysis of 48 U.S. Metropolitan Areas

Recent working paper

Injustice in transportation services experienced by disadvantaged demographic groups account for much of these groups’ social exclusion.

HoustonOppUnfortunately, there is little agreement in the field about what theoretical foundation should be the basis of measures of the justice of transportation services, limiting the ability of transportation professionals to remedy the issues. Accordingly, there is a need for an improved measure of the justice of the distribution of transportation services, which relates to the effectiveness of transportation services for all members of disadvantaged groups rather than for only segregated members of these disadvantaged groups. To this end potential measures of distributive justice, based on the accessibility to jobs provided by various modes, are evaluated in 48 of the top 50 largest metropolitan areas in the United States. The purpose of the study is to inform recommendations for appropriate use of each measure.

Accessibility Oriented Development

Recent working paper:

AoDMunicipal governments worldwide have been pursuing transit-oriented development (TOD) strategies in order to increase transit ridership, curb traffic congestion, and rejuvenate urban neighborhoods. In many cities, however, development of planned sites around transit stations has been close to non-existent, due to, among other reasons, a lack of coordination between transit investments and land use at the regional scale. Furthermore, the ability to access transit differs from the ability to access destinations that people care about. Reframing transit-oriented development as accessibility-oriented development (AOD) can aid the process of creating functional connections between neighborhoods and the rest of the region, and maximize benefits from transport investments. AOD is a strategy that balances accessibility to employment and the labor force in order to foster an environment conducive to development. AOD areas are thus defined as having higher than average accessibility to employment opportunities and/or the labor force; such accessibility levels are expected to increase the quality of life of residents living in these areas by reducing their commute time and encouraging faster economic development. To quantify the benefits of AOD, accessibility to employment and the labor force are calculated in the Greater Toronto and Hamilton Area, Canada in 2001 and 2011. Cross-sectional and temporal regressions are then performed to predict average commute times and development occurring in AOD areas and across the region. Results show that AOD neighborhoods with high accessibility to jobs and low accessibility to the labor force have the lowest commute times in the region, while the relationship also holds for changes in average commute time between the studied time periods. In addition, both accessibility to jobs and accessibility to the labor force are associated with changes in development, as areas with high accessibility to jobs and the labor force attract more development. In order to realize the full benefits of planned transit investments, planning professionals and policy makers alike should therefore leverage accessibility as a tool to direct development in their cities, and concentrate on developing neighbourhoods with an AOD approach in mind.

Kristin Carlson: Accessibility Impacts of Bus Access to Managed Lanes

Congratulations to Kristin Carlson for successfully defending her MS Thesis: “Accessibility Impacts of Bus Access to Managed Lanes” at the University of Minnesota Department of Civil, Environmental, and Geo- Engineering on August 22, 2017. The thesis will be made publicly available soon.

Figure 15: The absolute di↵erence in average job accessibility between the ML test scenario and baseline within 30 minutes by transit from 7 - 9 AM on Wednesday, October 5, 2016.
Figure 15: The absolute difference in average job accessibility between the ML test scenario and baseline within 30 minutes by transit from 7 – 9 AM on Wednesday, October 5, 2016.

This research introduces a method to measure changes in transit accessibility resulting from adjustments in bus-highway interactions. Operational differences between general purpose (GP) and managed lanes (ML) are measured using average travel time. Changes to transit travel time are systematically introduced to General Transit Feed Specification (GTFS) data through the use of the StopTimesEditor computer program developed for the purpose of this analysis. The methodology is tested on two express bus routes in the Minneapolis – St. Paul region (Twin Cities). The change in operating speed along portions of the selected transit routes is translated to changes in the job accessibility of the surrounding communities. The percent change in the worker-weighted average job accessibility for the area surrounding the transit routes and for the entire metropolitan region are 12% and 0.25% respectively. The methods introduced in this study can be used to evaluate the accessibility impacts of different highway operating environments for buses, or estimate the accessibility outcomes of different bus-highways scenarios.