Urban Engineering for Sustainability

Urban Engineering for Sustainability is a new book by my colleague and University of Illinois at Chicago professor Sybil Derrible. I reviewed a draft and wrote a blurb (below). It is fully interdisciplinary, and if you teach or are a student in the field, you should check it out.
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Endorsements
“Infrastructure in cities is often handled in different silos; Sybil Derrible’s is a rare book that breaks the mold, weaving our knowledge of infrastructure into our contemporary understanding of how cities function, integrating different systems and providing a new science for their design. Urban Engineering for Sustainability is essential reading for how we should renew our cities in making them ever more sustainable.”
—Michael Batty, University College London; author of Inventing Future Cities and The New Science of Cities

“Urban Engineering for Sustainability, by one of engineering’s few truly interdisciplinary thinkers, will be the benchmark text for anyone trying to understand how cities actually work. By considering the fully integrated nature of infrastructure systems, it serves as a useful antidote to the typically reductionist engineering curriculum.”
—David Levinson, Professor of Transport in the School of Civil Engineering, University of Sydney

“A timely textbook that takes a multi-infrastructure systems approach to developing sustainable and resilient cities. Key concepts are covered across multiple sectors, from basic principles to the latest advances. Civil and environmental engineers, sustainability scientists, and urban design professionals have long needed just such a textbook on integrated infrastructure engineering and design. Bravo!”
—Anu Ramaswami, Professor of Civil & Environmental Engineering and Director of the M.S. Chadha Center for Global India, Princeton University; Lead PI, Sustainable Healthy Cities Network

Transport Poverty| A Political Economy of Access

We are pleased to make available Chapter 21: Transport Poverty of A Political Economy of Access. It opens:

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

When we talk about access as a value that should guide transport policy, we need to address access for whom, not just access to where by what mode. In the auto-dependent US, the mode that offers the most access in most places currently is the car. Yet cars are expensive, and many people struggle with basic access (and mobility) simply because they can’t afford it. Transport is the second largest spending category for US households, behind only housing. This is the case even as transport is heavily subsidized, regardless of mode.1 As discussed in Subsidy,2 the general approach is to spread whatever help is offered thinly across infrastructure capital investment. This does little to help those with the least.

The Magic of Streetcars, The Logic of Buses | A Political Economy of Access

We are pleased to make available Chapter 11: The Magic of Streetcars, The Logic of Buses of A Political Economy of Access. It opens:

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

Once upon a time (1888 to be precise), the United States and the world launched a huge building boom for urban streetcars. Companies like Twin City Rapid Transit laid miles of track in fast-growing cities, extending well past the built areas to serve greenfield sites for emerging suburbs waiting to be platted and built. They did this because the streetcar promoters benefited directly from the land sales. The availability of a new, fast transit system connecting to downtown made houses much more valuable. The fares from the new passengers covered the operating costs of the system.

Subsidy | A Political Economy of Access

We are pleased to make available Chapter 4: Subsidy of A Political Economy of Access. It opens:

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

Should government subsidize transport? If government subsidizes transport, should it subsidize producers or consumers? If a government gave money to consumers, they could spend it on what they want, paying for a service, which if it covers operating costs, could lead to more investment. If it gave money directly to producers, they spend it on more supply. Which leads to a better outcome?

 

The automobile as prison. The city as freedom.

The automobile has been pitched as a machine for freedom. But you travel caged inside a small metal box, strapped to your chair, while your life is being threatened randomly by high speed two-ton projectiles, forced to keep eyes focused on the road and obliged to place hands at the 10 and 2 o’clock positions on the wheel, with your foot constrained to a small area on the floor. This doesn’t sound like freedom to me.

1925 Studebaker Patrol (Paddy) Wagon. Source: Wikipedia
1925 Studebaker Patrol (Paddy) Wagon. Source: Wikipedia

If you choose to enter a freeway, you are not even permitted to leave your car til you exit the road.

On streets, your behavior is governed by inanimate traffic lights, signs, and paint, which are violated at penalty of automatically generated fine or imprisonment.

This is all self-imposed, so it is more like committing yourself to an institution, the automobility asylum, perhaps, than prison which is imposed by others.

An alternative view is that freedom is not ensconced in a machine but in a way you can interact with the world. If you can, at your whim, when you want to, do what you want, engage in the activities you want, without fearing for your life, that is closer to freedom.

Jarrett Walker argues frequency is freedom. This is closer to the truth. While on a bus or train I am still caged in a metal box, it is a larger box, I am not strapped in, and I am much safer. I am also now free to do something with my time while in motion, not constrained to monitor the road.

And where can I travel in these safe freedom machines, reaching many more opportunities? Cities.  This gives a new meaning to the expression: Urban air makes you free.

‘But I can reach more places in a car than on transit in the same amount of time, almost everywhere,’ you argue. This is true, if you ignore the costs you impose on society, if you ignore the fixed costs of that opportunity to you, and if you ignore the ability to use time in some other way, as is available when not driving.

Freedom from car ownership, freedom from the obligation of driving, and freedom from negative externalities borne by the community at large are how we should reframe transport and land use goals. What can we do to give people those freedoms?

Access Quartet

I am pleased to have now completed my Access Quartet of books. These are artisanally selected from the last decade or so of my popular writings, including for the Transportist blog and elsewhere, along with new words to enhance their completeness.

They are organized so that they can be read independently, though an astute reader will identify several themes that run through them all, most obviously the need to privilege considerations of access when considering behavior, deploying technologies, designing infrastructure and networks, and deciding what to fund.

The books are beautifully laid out in the Tufte-latex template for clear information presentation and ease of reading. All are available in hardcover, paper, and PDF.

I thank my coauthors on the books, Kevin Krizek for The End of Traffic and the Future of Access, Kay Axhausen and Wes Marshall for Elements of Access, and David King for A Political Economy of Access for their contributions and extensive editing of my own writing. Each book also had numerous reviewers, who also made the books better.

You should read them all.

 

The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.
The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.
Spontaneous Access: Reflexions on Designing Cities and Transport by David Levinson
Spontaneous Access: Reflexions on Designing Cities and Transport by David Levinson
Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.
Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

It’s the (political) economy, stupid: when it comes to urban transport, we’re doing it wrong

Political choices, not technological innovations, shape our urban transport systems. As long as governments continue to prize mobility over accessibility, those systems will remain unhealthy and ineffectual.

[This is an edited extract from A Political Economy of Access by David M Levinson and David A King, available now in paper and PDF. It was published in Foreground.]

It is hard to examine the state of transport and land use planning without a large dose of cynicism about motives, and skepticism about claims and priorities.

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

Transport engineering and land use planning are technical fields nominally grounded in rational thought. Yet level-headed analysis and calculations haven’t led to healthy and financially sustainable transport and land use systems. Part of what we see as the problem is a focus on mobility over accessibility. This focus prioritizes vehicular flows and speed over people and proximity. Our shared goals should not be how to maximize how much people and things travel about. Rather, our goals should be about how society can make it as easy as possible to reach opportunities and activities. A second part of the problem is privileging expansion over preservation. In a world where transport is new with few roads and no transit service, expansion is the critical phase of development; but in today’s world of mature networks, preservation is so much more important. We identify numerous problems, but the solutions are difficult to implement. That is not, we believe, because they are not good ideas, but rather because the institutions that make decisions are incapable of implementing them.

Our political economy analysis explains how access is shaped by law, culture, and governance. The issues we raise are not new, either. It was a century ago when Frederick Law Olmstead, Jr. said:

“There has been a decided tendency on the part of official street planning to insist with quite needless and undesirable rigidity upon fixed standards of width and arrangement in regard to purely local streets, leading inevitably in many cases to the formation of blocks and lots of a size and shape ill adapted to the local uses to which they need  to be put.”

This quote introduces many of our concerns. First, streets and road networks are more than just thoroughfares. They actively shape the location and function of the built environment, support or deter alternatives to automobility and substantially affect public safety. Second, in a system where transport networks and land regulations are designed and built separately, there are mismatched incentives. The most efficient road may contradict the needs of great places. Speed is not necessarily a characteristic of great cities – other than maybe Indianapolis, no city brags about being a raceway. Third, rigid roadway design is a hallmark of a focus on mobility.  The road itself is simply a conduit through which one passes, and the quality of destinations is diminished. Lastly, these are just some of the well-known problems that have persisted a century later, yet we have spent far less effort trying to understand why we keep building cities that many consider undesirable.

An additional issue is that transport systems require coordination across actors. The car you own is worthless without roads, and the capital and expertise required to build and maintain cars very much differs from the expertise needed for roads. The question remains how to integrate infrastructure, traffic flow, and land development. We advocate for coordination through prices, so people can account for the full cost of the actions of themselves and others when making decisions, whether as a traveler, developer, planner, or elected official.

The current state of transport and land use systems raises further concerns. New technologies are changing transport in fundamental ways. App-based services offer new taxi-type alternatives, which compete with and complement existing travel modes. These services are backed by deep-pocketed investors and despite their popularity are, as of this writing, not actually profitable. But there is little doubt that such services will persist in some form once the money runs out. If the history of taxicabs is any guide, a new era of regulation will protect Uber, Lyft, and others from their demise.

Private firms have reoriented transport planning priorities, for good and bad. Not long ago long-range transport plans largely set the course for policy and investment decades ahead.  Now everything from streetcars for real estate development to ridesharing through dockless bikesharingand, the flavor of  the week, electric scooters, are undermining the slow predictability of policy. With automated vehicles peeking over the horizon, the conventional approach to transport planning may be obsolete as no one knows what innovations and unintended side effects automation will bring.

The internal combustion engine is likely nearing the end of its century of dominance. These engines use fuel, which is taxed to pay for infrastructure across the US and in some other countries, and taxed for general revenue elsewhere. A shift to electricity affects the core relationship between user fees and public spending. New sources of revenue will have to be developed, including road tolls, road access charges, parking fees, and other sources. Of course, a loss of motor fuel taxes also will affect who pays for infrastructure. The role of central governments will likely diminish as fuel taxes decline. This devolution of authority pushes local and state or provincial governments to raise their own revenues. Voters will be asked to approve new taxes and fees, which introduces many concerns, including whether voters are adequately informed to assess the value of any package of taxes and spending.

Transport referenda are generally popular with the public in the United States, for example, where more than 70 percent usually pass. But voters often don’t know the true details of what they are voting on. California has led the way in voter-led projects, including their high-speed rail (HSR) project that voters passed with 52.6% of the votes in 2008. Despite well-publicized concerns, proponents promised a train that would connect the state, “[C]arrying up to 117 million passengers annually by 2030, with the capacity to also carry high-value, lightweight freight.” Since then, the timeline has been extended, the scope scaled back, forecast recanted, and the costs have increased dramatically – at one point to nearly $100 billion. Stations have been delayed or cancelled, and now the train is promoted as a commuter service to open up housing markets away from the extremely expensive coastal cities. The project is substantially different from what voters were sold, and a very passive aggressive solution to the state’s housing affordability crisis. We expect more projects like this.

Lastly, the political economy of access must address issues of race and social justice. New transit investments tend to favor wealthier, whiter communities. Bicycle advocacy is dominated by young, white men, as are the technology companies developing micromobility, services and microtransit and taxi apps. As once-young, white men ourselves, there is nothing wrong with that, but we have learned it is but one perspective of many.

The value we wish to promote is access. Access is the ability for people and firms to interact, whether through employment, production, consumption or sales. Access is a value that differs from mobility. Where mobility improvements are a hallmark of recent decades of transport policy, our focus on mobility has led to auto dominated infrastructure that offers few other options about how to get around. With a focus on access, we can orient transport policy to connecting people to places they want to be, rather than accommodating driving at the expense of everything else.

The political aspects of transport policy shouldn’t be assumed away or treated as a nuisance. Political choices are the core reasons our cities look and function the way they do. Many of the transport and land use problems we want to solve already have technical solutions. What these problems don’t have, and what we hope to contribute, are political solutions.


This is an edited extract from A Political Economy of Access by David M Levinson and David A King, available now in paper and PDF.

Professor David Levinson joined the School of Civil Engineering at the University of Sydney in 2017. He taught at the University of Minnesota from 1999 to 2016 where he held the Richard P Braun/CTS Chair in Transportation (2006-2016). He was Managing Director of the Accessibility Observatory, and directed the Networks, Economics, and Urban Systems research group.

David A King is an Assistant Professor of Urban Planning at Arizona State University School of Geographical Sciences and Urban Planning. His research explores the impact of local transportation planning on the built environment, public finance, social equity and accessibility.

Now Available: A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions

Now available: A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King, in paper and PDF.

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

About the Book

Why should you read another book about transport and land use? This book differs in that we won’t focus on empirical arguments – we present political arguments. We argue the political aspects of transport policy shouldn’t be assumed away or treated as a nuisance. Political choices are the core reasons our cities look and function the way they do. There is no original sin that we can undo that will lead to utopian visions of urban life.

The book begins by introducing and expanding on the idea of Accessibility. Then we proceed through several major parts: Infrastructure Preservation, Network Expansion, Cities, and Institutions. Infrastructure preservation concerns the relatively short-run issues of how to maintain and operate the existing surface transport system (roads and transit). Network expansion in contrast is a long-run problem, how to enlarge the network, or rather, why enlarging the network is now so difficult. Cities examines how we organize, regulate, and expand our cities to address the failures of transport policy, and falls into the time-frame of the very long-run, as property rights and land uses are often stickier than the concrete of the network is durable. In the part on Institutions we consider things that might at first blush appear to be short-run and malleable, are in fact very long-run. Institutions seem to outlast the infrastructure they manage.

Many of the transport and land use problems we want to solve already have technical solutions. What these problems don’t have, and what we hope to contribute, are political solutions. We expect the audience for this book to be practitioners, planners, engineers, advocates, urbanists, students of transport, and fellow academics.


Table of Contents

Preface

1 Accessibility

  • 1.1  The duty of the sovereign
  • 1.2  Access as efficiency
  • 1.3  Access as equity
  • 1.4  Why A Political Economy of Access?

I Infrastructure Preservation

2 Hierarchy of Needs

  • 2.1  The nature of need
  • 2.2  The state of infrastructure
  • 2.3  Infrastructure triage
  • 2.4  Report cards
  • 2.5  Infrastructure heal thyself

3 Road Revenues

  • 3.1  From Snicker’s Gap to funding gap
  • 3.2  How the gas tax may fail
  • 3.3  Fix-it-first

4 Subsidy

  • 4.1  Car subsidies
  • 4.2  Bicycle subsidies
  • 4.3  Transit subsidies
  • 4.4  Subsidize users not systems
  • 4.5  Refactoring subsidies

5 The Solution to Congestion

  • 5.1 Welcome to the club
  • 5.2  Supply-side solutions
  • 5.3  Demand-side solutions

6 Pricing

  • 6.1  Temporal variations
  • 6.2  Spatial variations
  • 6.3  You can toll some of the roads some of the time
  • 6.4  You can toll some of the cars some of the time: Phasing in road pricing one vehicle at a time
  • 6.5  Billing systems
  • 6.6  Road service providers
  • 6.7  What about the revenues?
  • 6.8  Planning with prices
  • 6.9  Congestion is over! If you want it

7 Externalities

  • 7.1  Pecuniary and technical externalities
  • 7.2  Negative externalities
  • 7.3  Positive externalities
  • 7.4  Are reductions of negative externalities positive externalities?
  • 7.5  Pollution ethics
  • 7.6  The art of noise
  • 7.7  Safety vs. speed

8 The Solution to Pollution and Greenhouse Gases

  • 8.1  Global warming
  • 8.2  Supply-side solutions
  • 8.3  Demand-side solutions
  • 8.4  Pollution trust funds
  • 8.5  Domain alignment

II Network Expansion

9 Hierarchy of Wants

  • 9.1 Transport costs too much
  • 9.2 Transport benefits too little
  • 9.3 Transport takes too long to build
  • 9.4 Benefit/cost analysis
  • 9.5 Big infrastructure

10 Macroeconomics: Is Transport Stimulating?

11 The Magic of Streetcars, the Logic of Buses

  • 11.1 Ride quality
  • 11.2 Speed
  • 11.3 Operating costs
  • 11.4 Navigability
  • 11.5 Payment and boarding times
  • 11.6 Nostalgia
  • 11.7 Novelty
  • 11.8 Conspiracy
  • 11.9 Amenity
  • 11.10 Sexuality
  • 11.11 Respect
  • 11.12 Status
  • 11.13 Pedestrian accelerator
  • 11.14 Traffic calming
  • 11.15 Superstructure
  • 11.16 Feedback
  • 11.17 Congestion reduction
  • 11.18 Transportainment
  • 11.19 Permanence and directness
  • 11.20 Development-oriented transit
  • 11.21 Discussion

III Cities

12 Clustering

  • 12.1 Multi-sided markets
  • 12.2 Clustering and economic development
  • 12.3 Constraints drive growth
  • 12.4 Simpli-City
  • 12.5 Beyond density
  • 12.6 Competing centers

13 Zoning

  • 13.1 Zoning tries to solve the externalities problem
  • 13.2 Height limits
  • 13.3 Should the Bay Area have 11 million residents?

14 Fielding Dreams

  • 14.1 Defining induced demand
  • 14.2 Induced demand can be a good thing
  • 14.3 Forgetting faster than we learn

15 Trains, Planes, and Automobiles

  • 15.1 Mapping high-speed rail
  • 15.2 A national high-speed rail network
  • 15.3 Nationalize the rails
  • 15.4 Supercities

16 Value Capture and the Virtuous Cycle

  • 16.1  Infrastructure create saccess
  • 16.2  Access creates value
  • 16.3  Value can be captured
  • 16.4  Captured value can fund infrastructure
  • 16.5  Policy implications

IV Institutions

17 Devolve Responsibility

  • 17.1  Subsidiarity
  • 17.2  Ending the federal surface-transport program .
  • 17.3  Transport finance without the feds: The Canadian model
  • 17.4  Transit federalism
  • 17.5  Whose values?
  • 17.6  ‘Dogfooding’: Ensure managers use the system
  • 17.7  Should voters have full information when voting on transport projects?
  • 17.8  Coordinate local transport and land use policies
  • 17.9  Department of Accessibility
  • 17.10  Metropolitan Department for Transport
  • 17.11  The lump of government mistake

18 Private | Public

  • 18.1  Ownership and network size
  • 18.2  Public-private partnerships
  • 18.3  Tender routes
  • 18.4  Thought experiment: Auctioning green time
  • 18.5  Asset recycling

19 Utility Models for Transit and Roads

  • 19.1  What is a Utility?
  • 19.2  TransLink: organizing transport like a utility
  • 19.3  Transit should focus on core markets
  • 19.4  Think of transit like a club
  • 19.5  Enterprising roads
  • 19.6  Minnesota Mobility: A scenario
  • 19.7  Takeaways

20 Politics and Politicians

  • 20.1 Political parties, three axes, and public transport
  • 20.2  Trust as a positive externality
  • 20.3  Lying as a vicious cycle
  • 20.4  It’s a success
  • 20.5  Mischief in Minnesota
  • 20.6  Taking credit
  • 20.7  Expertise
  • 20.8  Frontiers or values as instruments

21  Transport Poverty

22  Pretexts of Safety and Justice

  • 22.1  Safe Streets for All
  • 22.2  Racial Bias in Traffic Enforcement
  • 22.3  US police interactions are needlessly violent
  • 22.4  Why is traffic safety used as a pretext?
  • 22.5  Not in our name

V Conclusions

23 Jam Today, Access Tomorrow, or Six Impossible Things Before Breakfast

Appendices

A Goods Framework

  • A.1 Rivalry and excludability
  • A.2 Goods and roads
  • A.3 Goods and transit
  • A.4 Anti-rivalry and anti-excludability

B Network Economies, Supply and Demand

C The Price of Privacy

D Governance and Performance

  • D.1 Introduction
  • D.2 Governance
  • D.3 Performance of state highway systems
  • D.4 Analysis
  • D.5 Conclusions

E Long Range Funding Solutions

Postscript: Homo Gridicus

Bibliography


Features

  • 470 pages.
  • Color Images.
  • ISBN: 9780368349034
  • Publisher: Network Design Lab

Purchase

How more development can lead to less travel: Examples

The 30-Minute City by David M. Levinson
The 30-Minute City by David M. Levinson 

Balancing housing and jobs, so that they are located near each other, logically reduces travel compared to a situation where those same jobs are far apart. This has long been understood in the transport planning community (see e.g. Cervero 1989, or my 1998 paper), but is not well grasped among the general public.

However, moving a fixed number of things around is not how cities actually grow. Telling place A you taking away their employment is controversial. More generally new things are added.

Development in Mascot. Photo by author.
Development in Mascot. Photo by author.

It is commonly asserted that more development adds to congestion. And often this is true. But not always, it depends on the type of development. More housing in a housing-rich and job-poor area will result in more total travel. More employment in a job-rich, housing poor area will do similarly. More housing in a job-rich area, and more jobs in a housing-rich area can actually reduce travel.

For our baseline case, imagine a city with two precincts separated by 2 km.

Precinct A: 1000 Jobs, 0 Resident Workers

Precinct B: 0 Jobs, 1000 Resident Workers.

The one-way (morning commute) trip table looks like:

Jobs 1000 0
Workers A B
0 A 0 0
1000 B 1000 0

Total daily travel to work is 2000 person km per day. (Everyone commutes from B to A). Travel on Link BA is 1000 at 2 km per trip, or 2000 person km traveled. (This just analyzes one-way trips. Round trip commutes would double this.)

Case 1. 

There is a proposal to intensify development in Precincts A and B, so each is more locally balanced.

Precinct A: 1000 Jobs, 500 Resident Workers

Precinct B: 500 Jobs, 1000 Resident Workers.

The new one-way (morning commute) trip table looks like (rounded):

Jobs 1000 500
Workers A B
500 A 498 2
1000 B 503 497
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

The Daily Travel on links:

AB = 2 @ 2 km

BA = 503 @ 2 km

within A = 498 @ 0.5 km (walking)

within B = 497 @ 0.5 km

TOTAL = 1507 pkt.

This is considerably less than the baseline case as many more travelers can reach their destinations locally. While there is still some commuting, it is far less than before.

Case 2.

There is a proposal to build a locally-balanced Precinct C halfway between Precincts A and B.

Precinct C has 500 Jobs and 500 Workers

The new one-way (morning commute) trip table looks like:

Jobs 1000 0 500
Workers A B C
0 A 0 0 0
1000 B 666.666667 0 333.333333
500 C 333.333333 0 166.666667
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

The Daily Travel on links:

BC = BA + BC = 1000 @ 1 km

CA = BA + CA = 1000 @ 1 km

within C = 166 trips @ 0.5 km

TOTAL = 2083 pkt.

In this example, the total person kilometers traveled (pkt) on the links connecting inter-city precincts is essentially identical to the base case, despite adding 500 residents and 500 workers halfway between each. There are an additional 167 pkt daily on the intrazonal market (within C), which is likely walking.

The total one-way commute travel per person however drops, from 2 km/person per day to about 1.38 km/person per day. The average trip length is reduced. The experienced travel is thus about one-third lower.

Case 3

Building on Case 1, completely balancing A and B (so each has 1000 jobs and 1000 workers) reduces one-way commutes further (to 1176 pkt)

The new one-way (morning commute) trip table looks like (rounded):

Jobs 1000 1000
Workers A B
1000 A 941 59
1000 B 59 941
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

So, it should be clear from this example that adding development can actually reduce total travel, if it is the right kind of development in the right places.

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King