Recently in Retroblogging Category

Recently published:

Zhang, Lei and David Levinson (2009) The Economics of Road Network Ownership: An Agent-Based Approach. International Journal of Sustainable Transport Sept. 2009 3(5) pp. 339-359. [doi]

This paper explores the economic impact of alternative ownership structures on transportation system performance, social welfare, and regulatory needs. Road pricing, investment, and ownership decisions are jointly considered in an agent-based evolutionary model applicable to large networks. Results suggest that a centralized public regime with average-cost pricing is far from socially optimal with even moderate demand growth. When properly regulated, a completely privatized transportation network could achieve net social benefits close to the theoretical optimum and distribute a high percentage of welfare gains to travelers. But an unregulated private road economy would suffer from higher-than-optimal tolls and overinvestment.

Keywords: network economics; privatization; road pricing; simulation of network evolution; transportation financing

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.

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

Recently published:

Zhang, Lei and David Levinson (2008) Determinants of Route Choice and the Value of Traveler Information: A Field Experiment. Transportation Research Record: Journal of the Transportation Research Board 2086:81-92 [doi]

A major strategy of federal ITS initiatives and state departments of transportation is to provide traveler information to motorists through various means, including variable message signs, the internet, telephone services like 511, in-vehicle guidance systems, and TV and radio reports. This is relatively uncontroversial, but its effectiveness is unknown. Drivers receive value from traveler information in several ways, including the ability to save time, but perhaps more importantly, other personal, social, safety, or psychological impacts from certainty. This information can be economically valued. The benefits of reduction in driver uncertainty when information is provided at the beginning of the trip by various means is the main variable we aim to measure in this research, in which we assess user preferences for routes as a function of the presence and accuracy of information, while controlling for other trip and route attributes, such as trip purpose, travel time, distance, number of stops, delay, esthetics, level of commercial development, and individual characteristics. Data is collected in a field experiment in which more than 100 drivers, given real-time travel time information with varying degrees of accuracy, drove four of five alternative routes between a pre-selected OD pair in the Twin Cities metro area. Ordinary regression, multinomial, and rank-ordered logit models produce estimates of the value of information with some variation. In general, results show that travelers are willing to pay up to $1 per trip for pre-trip travel time information. The value of information is higher for commute and event trips and when congestion on the usual route is heavier. The accuracy of the traveler information is also a crucial factor. In fact, there do not seem be incentives for travelers to use traveler information at all unless they perceive it to be accurate. Finally, most travelers (70%) prefer that such information should be provided for free by the public sector, while some (19%) believe that it is better for the private sector to provide such service at a charge. Over 35% of subjects are willing to pay for OD-customized pre-trip travel time information.

Keywords: Value of Information, Advanced Traveler Information System (ATIS), Real-Time Traffic Operations, Travel Behavior, Spatial behavior, Wayfinding Behavior, Route Choice.

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

Recently published:

Iacono, Michael, David Levinson and Ahmed El-Geneidy (2008) Models of Transportation and Land Use Change: A Guide to the Territory Journal of Planning Literature 22: 323-340.

Modern urban regions are highly complex entities. Despite the difficulty of modeling every relevant aspect of an urban region, researchers have produced a rich variety of models dealing with interrelated processes of urban change. The most popular types of models have been those dealing with the relationship between transportation network growth and changes in land use and the location of economic activity, embodied in the concept of accessibility. This article reviews some of the more common frameworks for modeling transportation and land use change, illustrating each with some examples of operational models that have been applied to real-world settings. It then identifies new directions for future research in urban modeling and notes the important contributions of the field to date.

Key Words: transportation planning • land use • mathematical models • urban growth • gravity model • microsimulation

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

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.

The following was recently published:

Corbett, Michael, Feng Xie, and David Levinson (2009) Evolution of the Second-Story City: The Minneapolis Skyway System. Environment
and Planning b
36(4) 711-724 [doi]

This paper describes and explains the growth of the Minneapolis Skyway network. Accessibility is used as a major factor in understanding that growth (i.e. does the network connect to the location(s) with the highest accessibility, followed by the second highest, and so on). First, employment opportunities are used as the measure of activity and are based off of the square footage of buildings and/or ITE trip generation rates. Using information about the buildings located downtown for each year since the first skyway was built, the accessibilities of each of the connected and adjacent unconnected blocks were calculated for every time period the skyway system expanded. The purpose is to determine how often the expansion connected the block with the highest accessibility. The results show that though important, accessibility was rarely maximized, except in the early stages of development. A connect-choice logit model relating the probability of joining the network (in a given year) to accessibility and network size was employed. The results show accessibility does remain an important factor in predicting which links are connected. Physical difficulties in making connections may have played a role, as well as the potential for adverse economic impacts.

Keywords: Network growth, Skyways, Minneapolis

Rational Locator

Levinson, David and Ajay Kumar (1994) The Rational Locator: Why Travel Times Have Remained Stable. Journal of the American Planning Association, Summer 1994 60:3 319-332.

This paper evaluates household travel surveys for the Washington metropolitan region conducted in 1968 and 1988, and shows that commuting times remain stable or decline over the twenty year period despite an increase in average travel distance, after controlling for trip purpose and mode of travel. The average automobile work-to-home time of 32.5 minutes in both 1968 and 1988 is, moreover, very consistent with a 1957 survey showing an average time of 33.5 minutes in metropolitan Washington. Average trip speeds increased by more than 20 percent, countering the effect of increased travel distance. This change was observed during a period of rapid suburban growth in the region. With the changing distributional composition of trip origins and destinations, overall travel times have remained relatively constant. The hypothesis that jobs and housing mutually co-locate to optimize travel times is lent further support by these data.

David Levinson

Network Reliability in Practice

Evolving Transportation Networks

Place and Plexus

The Transportation Experience

Access to Destinations

Assessing the Benefits and Costs of Intelligent Transportation Systems

Financing Transportation Networks

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