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January 15, 2010

Designing highways the slime mould way

From New Scientist: Designing highways the slime mould way

... Jeff Jones and Andrew Adamatzky, specialists in unconventional computing at the University of the West of England in Bristol, wondered if biology could provide an alternative to conventional road planning methods. To find out, they created templates of the UK using a sheet of agar on which they marked out the nine most populous cities, excluding London, with oat flakes. Then, in the place of London, the pair introduced a colony of P. polycephalum, which feeds by spawning tendrils to reach nutrients, and recorded the colony's feeding activity (see picture).

Most of the resulting "maps" mimicked the real inter-city road network, but some offered new routes. For instance, the motorway between Manchester and Glasgow passes along the west coast of the UK, but the slime mould preferred to travel east to Newcastle and then north to Glasgow ( /arxiv.org/abs/0912.3967 ). "This shows how a single-celled creature without any nervous system - and thus intelligence in the classical sense - can provide an efficient solution to a routing problem," says Jones.

November 16, 2009

The Block

Via DK: The Block: The Complete History of Eldridge Street Between Stanton and Rivington. Nice animation by Zach van Schouwen.

August 30, 2009

Agent-Based Model of Price Competition and Product Differentiation on Congested Networks

Recently published:

Zhang, Lei, David Levinson, and Shanjiang Zhu (2008) Agent-Based Model of Price Competition and Product Differentiation on Congested Networks. . Journal of Transport Economics and Policy Sept. 2008 42(3) pp. 435-461. [download]

Using consistent agent-based techniques, this research explores the welfare consequences of product differentiation on congested networks. The economic analysis focuses on the source, evolution, measurement, and impact of product differentiation with heterogeneous users on a mixed ownership network. Path differentiation and space differentiation are defined and measured for a base scenario and several variants. The findings favour a fixed-rate road pricing policy compared to complete pricing freedom on toll roads. It is also shown that the impact of production differentiation on welfare is not always positive and depends on the level of user heterogeneity.

August 29, 2009

Investing for Reliability and Security in Transportation Networks

Recently published:

Zhang, Lei, and David M. Levinson (2008) Investing for Reliability and Security in Transportation Networks. Transportation Research Record: Journal of the Transportation Research Board #2041 pp.1-10 [doi]

Alternative transportation investment policies can lead to very different network forms in the future. The desirability of a transportation network should be assessed not only by its economic efficiency but also reliability, because the cost of incidental capacity loss in a road network can be massive. This research concerns how investment rules shape the hierarchical structure of roads, and affects network fragility with regard to natural disasters, congestion, and accidents and vulnerability to targeted attacks. A microscopic network growth model predicts the equilibrium road networks under two alternative policy scenarios: investment based on benefit cost analysis or bottleneck removal. A set of Monte-Carlo simulation runs, in which a certain percentage of links are removed according to the type of network degradation analyzed, are carried out to evaluate the equilibrium road networks. It is found that hierarchy exists in road networks for reasons such as economic efficiency, but an overly hierarchical structure has serious reliability problems. Throughout the equilibrating or evolution process, the studied grid network under benefit cost analysis has better efficiency performance, as well as error and attack tolerance. The policy implication from these findings is that benefit-cost analysis should be preferred to myopic bottleneck-removal type of investment rules, no matter how the planning horizon is specified.

Keywords: Transportation network dynamics, road growth model, reliability, vulnerability, fragility, road investment and financing policy

August 27, 2009

The Weakest Link: The decline of the surface transportation networks

Recently published:

Xie, Feng and David Levinson (2008) The Weakest Link: A model of the decline of surface transportation networks. Transportation Research part E 44(1) 100-113. [doi]

This study explores the economic mechanisms behind the decline of a surface transportation network, based on the assumption that the decline phase is a spontaneous process driven by decentralized decisions of individual travelers and privatized links. A simulation model is developed with a degeneration process by which the weakest link is removed iteratively from the network. Experiments reveal how the economic efficiency of a network evolves during the degeneration process and suggest an "optimal" degenerated network could be derived during the decline phase in terms of maximizing total social welfare.

Keywords: Decline; Transportation network; Simulation; Welfare; Accessibility


August 26, 2009

New UK high-speed rail plan unveiled

From the BBC New UK high-speed rail plan unveiled

The line would serve Birmingham and Manchester, getting passengers from Glasgow to London in just two hours and 16 minutes, the rail firm said. It rejected several alternative routes, including the east of England.

Judging from the map (linked below), the architecture of the line is clearly to feed London, all of the ancillary cities are as if on a tree with the xylem and phloem oriented to London, it would not be terribly good for say Manchester to Edinburgh or Manchester to Birmingham.

"The firm said that the line would account for 43.7 million journeys per year by 2030, which would result in 3.8 million fewer vehicle journeys and fewer carbon dioxide emissions.".
In other words, more 90% of the trips are switching from rail or air to HSR. Providing better rail service to existing rail passengers is a good thing, but CO2 is hardly a rationale (as more CO2 has to be used going faster than going slower if the electricity is from the same place ... diesel to electric conversion is a separate matter).

Finally, the cost is esimated at $55B for 1500 miles of rail (presumably including triple or quadruple tracking in some sections. Planning will take 5 more years. It is hoped by the promoters the first section (London to Birmingham) will open in 2020. Speeds will max at 200 mph.


rail plan

Birmingham: 45mins, down from 1h 22mins

Liverpool: 1hr 23mins, down from 2hrs 8mins

Manchester: 1hr 6mins, down from 2hrs 7mins

Edinburgh: 2hrs 9mins, down from 4hrs 23mins

Glasgow: 2hrs 16mins, down from 4hrs 10 mins


Also see: London to Glasgow in five minutes, a video showing the West Coast Main Line (which this proposal seems to duplicate) and was recently modernized for 9 billion pounds.

August 24, 2009

Jurisdictional Control and Network Growth

Recently published:

Xie, Feng and David Levinson (2009) Jurisdictional Control and Network Growth. Networks and Spatial Economics 9(3) 459-483. [doi]

Transport infrastructure evolves over time in a complex process as part of a dynamic and open system including travel demand, land use, as well as economic and political initiatives. As transport infrastructure changes, each traveler may adopt a new schedule, frequency, destination, mode, and/or route, and in the long term may change the location of their activities. These new behaviors create demand for a new round of modifications of infrastructure. In the long run, we observe the collective change in the capacity, service, connectivity, and connection patterns (topology) of networks. This paper examines how a fixed set of places incrementally gets connected as transport networks are constructed and upgraded over time. A simulator of network incremental connection (SONIC) is constructed to model the process of incremental connections and examines how networks evolve differently under centralized versus decentralized jurisdictional initiatives. Exploring the mechanism underlying this dynamic process can answer questions such as how urban networks have developed into various topologies, which network patterns are more efficient, and whether and how transport engineers, planners, and decision makers can guide the dynamics of land uses and infrastructure in a desired direction.

Keywords Network growth - Transport economics - Incremental connection - Jurisdictional control

August 23, 2009

Modeling the Growth of Transportation Networks: A comprehensive review

The following was recently published:

Xie, Feng and David Levinson (2009) Modeling the Growth of Transportation Networks: A comprehensive review. Networks and Spatial Economics. 9(3) 291-307. [doi]

This paper reviews the progress that has been made over the last half-century in modeling and analyzing the growth of transportation networks. An overview of studies has been provided following five main streams: network growth in transport geography; traffic flow, transportation planning, and network growth; statistical analyses of network growth; economics of network growth; and network science. In recognition of the vast advances through decades in terms of exploring underlying growth mechanisms and developing effective network growth models, the authors also point out the challenges that are faced to model the complex process of transport development.

August 22, 2009

Topological evolution of surface transportation networks

The following was recently published:

Xie, Feng and David Levinson (2009) The Topological Evolution of Road Networks.
Topological evolution of surface transportation networks
Computers, Environment, and Urban Systems 33(3) 211-223 [doi]

This study explores the topological evolution of surface transportation networks, using empirical evidence and a simulation model validated on that data. Evolution is an iterative process of interaction, investment, and disinvestment. The temporal change of topological attributes for the network is also evaluated using measures of connectivity, density, heterogeneity, concentration, and connection patterns. The simulation model is validated using historical data from the Indiana interurban network. Statistical analyses suggest that the simulation model performs well in predicting the sequence of link abandonment in the interurban network as well as the temporal change of topological attributes. The simulation model is then applied on different idealized network structures. Typical connection patterns such as rings, webs, hub-and-spokes, and cul-de-sacs emerge in the networks; the spontaneous organization of network hierarchies, the temporal change of spacing between parallel links, and the rise-and-fall of places in terms of their relative importance are also observed, providing evidence for the claim that network topology is an emergent property of network dynamics.

PACS numbers: 89.75.Fb, 89.75.-k, 89.75Kd

August 10, 2009

Special Issue on the Evolution of Transportation Network Infrastructure in Networks and Spatial Economics: Volume 9, Issue 3 (2009)

A special issue of Networks and Spatial Economics on the Evolution of Transportation Network Infrastructure, for which I was the editor, is now out. Many thanks to my co-authors and the journal for making this happen. (I cannot however see the final version, as it is behind a pay-wall and my university does not yet subscribe to the journal. I have read all of the articles though, and it is well worth reading if you do have access).

Introduction to the Special Issue on the Evolution of Transportation Network Infrastructure
David Levinson
289-290

Modeling the Growth of Transportation Networks: A Comprehensive Review
Feng Xie and David Levinson
291-307

Inter-Modal Network Externalities and Transport Development: Evidence from Roads, Canals, and Ports During the English Industrial Revolution
Dan Bogart
309-338

The Efficiency of the Victorian British Railway Network: A Counterfactual Analysis
Mark Casson
339-378

Graph-Theoretical Analysis of the Swiss Road and Railway Networks Over Time
Alexander Erath, Michael Löchl and Kay W. Axhausen
379-400

Co-evolution of Density and Topology in a Simple Model of City Formation
Marc Barthélemy and Alessandro Flammini
401-425

The Topology of Transportation Networks: A Comparison Between Different Economies
Efrat Blumenfeld-Lieberthal
427-458

Jurisdictional Control and Network Growth
Feng Xie and David Levinson
459-483

May 20, 2009

More historical transportation networks

Via WC: A series of historical photos and maps of Chicago and other
Streetcars

Via DK: A neat animation of NYC subway ridership from 1905-2006:
NYC Subway Ridership, 1905-2006

June 18, 2008

Diffusion of Wal-Mart

An interesting paper on the spatial diffusion of Wal-Mart across the United States by Thomas Holmes: The Diffusion of Wal-Mart and Economies of Density

and

A YouTube Movie

April 19, 2007

Russia Plans World's Longest Tunnel, a Link to Alaska

Russia Plans World's Longest Tunnel, a Link to Alaska

April 18 (Bloomberg) -- Russia plans to build the world's
longest tunnel, a transport and pipeline link under the Bering Strait to Alaska, as part of a $65 billion project to supply the U.S. with oil, natural gas and electricity from Siberia. ... more.

This reminds one of Buckminster Fuller, who long ago advocated linking the world's electrical grids to balance loads (assuming low losses on transmission). Looking at his Dymaxion Map gives a new perspective on how close Alaska and Siberia are.

March 16, 2007

Topology of Urban Transportation Networks

The Urban Economics blog has an interesting post by Efrat Blumenfeld-Lieberthal, who I met while visiting Michael Batty's CASA shop at UCL: Topology of urban transportation networks. It was nice to see correlations between economic development and network structure for intercity networks.

March 3, 2007

The Co-Evolution of London's Land Use and Transport

updated August 25, 2009:

For those of you who doubt I am doing work over in London, I have completed two other papers (in addition to "Too Expensive to Meter" based on my research over here):

  • Levinson, David (2008) The Orderliness Hypothesis: Does Population Density Explain the Sequence of Rail Station Opening in London? Journal of Transport History 29(1) March 2008 pp.98-114.[download]
  • Network growth is a complex phenomenon. Some have suggested that it occurs in an orderly or rational way, based on the size of the places that are connected. David Levinson examines the order in which stations were added to the London surface rail and Underground rail networks in the nineteenth and twentieth centuries, testing the extent to which order correlates with population density. While population density is an important factor in explaining order, he shows that other factors were at work. The network itself helps to reshape land uses, and a network that may have been well ordered at one time may drift away from order as activities relocate.


  • Levinson, David (2008) Density and Dispersion: The Co-Development of Land use and Rail in London. Journal of Economic Geography 8(1) 55-57.
    JEG: [doi]
  • This article examines the changes that occurred in the rail network and density of population in London during the 19th and 20th centuries. It aims to disentangle the 'chicken and egg' problem of which came first, network or land development, through a set of statistical analyses clearly distinguishing events by order. Using panel data representing the 33 boroughs of London over each decade from 1871 to 2001, the research finds that there is a positive feedback effect between population density and network density. Additional rail stations (either Underground or surface) are positive factors leading to subsequent increases in population in the suburbs of London, while additional population density is a factor in subsequently deploying more rail. These effects differ in central London, where the additional accessibility produced by rail led to commercial development and concomitant depopulation. There are also differences in the effects associated with surface rail stations and Underground stations, as the Underground was able to get into central London in a way that surface rail could not. However, the two networks were weak (and statistically insignificant) substitutes for each other in the suburbs, while the density of surface rail stations was a complement to the Underground in the center, though not vice versa.


Perhaps more interesting for the non-academic, we (Ahmed El-Geneidy, Feng Xie, and myself of the Nexus group) have put together three quicktime movies


  • 1.The co-evolution of London population density and surface (National) rail

  • 2.The co-evolution of London population density and the Underground

  • 3.The co-evolution of London population density and surface (National) rail and the Underground


These can be accessed from here.

September 14, 2006

Clash of Speeds

In the Tofflers' new book "Revolutionary Wealth", the discuss the "Clash of Speeds", saying in an interview

"If you were a cop at the side of the road monitoring the speed of the cars going by, you would clock the car of business,which is always changing rapidly under competitive pressures,at 100miles per hour.But the car of education,which is supposedly preparing our young for the future,is only going 10mph.You cannot have a successful economy with that degree of de-synchronization. "

If education is going 10mph, one might posit surface transportation itself is going 1 mph. The networks we use are perhaps the slowest of institutions to change, the roads we use today are still where we put them a decade, a century, or a millenium (or two) ago. This slow pace of change is a two-way street. If you want to make rapid change, you will be frustrated, but if you want to make lasting change, you will be rewarded.

February 25, 2004

Understanding highway network growth

There is a nice summary of our recent empirical work on modeling network growth, the project "If They Come, Will You Build It," written up here:


Article


The final report is here:


Final Report