William R. Black

Sustainable transportation: a US perspective

Abstract It is argued that the current petroleum-based motor vehicle highway system is not sustainable due to the finite nature of petroleum reserves, air quality problems, global atmospheric problems, excessive fatalities, congestion and urban sprawl. The solutions to the sustainability problem as proposed in the literature are reviewed based on their application in the USA and are found to be ineffective. A summary of the US actions in the aftermath of the Rio Earth Summit suggests that little is being done to solve the overall sustainability problem. It is recommended that a unified, cooperative effort be initiated by the USA, Europe and perhaps Japan to resolve this problem.

Accidents on belgium's motorways: a network autocorrelation analysis

A method of assessing the extent to which the value of a variable on a given segment of a network influences values of that variable on contiguous segments is examined here. The method uses network autocorrelation analysis, a network variant of spatial autocorrelation analysis, and Morans I statistic to make the assessment. Illustrations of positive and negative network autocorrelation are given and interpreted for several simple linear networks. An empirical sampling distribution for the case of a ten link network is derived based on 100000 samples; this distribution is compared with a normal distribution and found not to be significantly different. Use of network autocorrelation analysis with more complex networks is demonstrated using 1991 motor vehicle accident rates for a portion of the motorway network of Belgium. A significant level of positive network autocorrelation is observed. It is further demonstrated that the source of the observed positive covariation can be identified using a secondary analysis that focuses on the motorway and ring road components of the overall system to identify those portions of the network that are the major sources of the positive autocorrelation. A further analysis reveals that the major sources of this positive covariation have been properly identified.

AN UNPOPULAR ESSAY ON TRANSPORTATION

Several popular notions exist in the transportation and transport geography literature that should more properly be viewed as popular myths. Several of these myths are examined using a combination of existing research, data analysis and certain theoretical constructs. Among the areas addressed are transport and economic development, the likelihood of telecommuting reducing urban travel, the promise of ethanol as an alternative transport fuel, the future demand for public transit by senior citizens, the role of network connectivity in accessibility and economic growth, and the relationship between vehicle speed and motor vehicle accidents. An examination of several of these myths and some others reveals that they clearly need to be researched in further detail, or in other cases they are patently wrong.

Spatial interaction modeling using artificial neural networks

Abstract Artificial neural networks using traditional gravity model components are proposed as an alternative to the fully constrained gravity model. Drawn primarily from the cognitive science area of artificial intelligence, these non-linear models are exceptionally good at recognizing patterns in data. At the same time these neural network models are more flexible and more accurate. When used with the traditional components of the gravity model, neural network models require the estimation of far fewer coefficients than fully constrained gravity models. In comparison with those latter models, the application of the gravity artificial neural network (GANN) models to seven sets of commodity flows yields errors that are 30% to 50% smaller. Questions of input significance and network autocorrelation are also addressed.

From Global Warming to Sustainable Transport 1989-2006

ABSTRACT Beginning with a review of a 1990 article on the impact of global warming on the transportation infrastructure, this article summarizes the changes in our knowledge of climate change and its impact on transport over the past sixteen years. Although most of the basic scientific knowledge has not changed there has been an increase in our understanding of the potential impacts. It is noted that this field of study has evolved from the pure concern for global warming into a general concern for sustainable transportation and the other factors that make transport non-sustainable: local air quality problems, injuries and fatalities from motor vehicle incidents, petroleum resource depletion and congestion, as well as concerns over what can be done about the various negative externalities of transportation today. It is the field of sustainable transport broadly defined that now dominates nearly all research in transport.

An analysis of gravity model distance exponents

This study examines variations in the basic parameter of the gravity model: the distance or travel time exponent. In a conceptual examination of the exponent under ideal conditions, it is noted that the exponent will be low if either production or consumption of the phenomena is geographically concentrated. It is further noted that if all regions produce and consume the phenomena, this generally implies a large number of substitute regions, and therefore a large exponent. These three variables are made operational and related to a set of eighty exponents for 1967 commodity flows in the United States. A multiple regression model is derived and utilized to estimate the exponents. The latter are then used to reestimate the flows. The root mean squared errors are quite similar for the fitted and estimated exponents. Implications of the research appear to be consistent with variations of the exponent in the urban context.

MODELING SAUDI ARABIA-BAHRAIN CORRIDOR MODE CHOICE.

Intercity mode choice in the Saudi Arabia-Bahrain corridor is analyzed using disaggregate transport mode choice models. Two separate models are developed, one for the Riyadh-Bahrain corridor and the other for the Eastern Province-Bahrain corridor. These models are more accurate than previous mode choice models; the ϱ-square and its adjusted variant are over 0.9 for the Riyadh-Bahrain model and over 0.8 for the Eastern Province-Bahrain model. These significant results are due partially to the use of disaggregate data; survey data on individual choices and attributes were used here. The study also uses several socioeconomic variables (eg immediate decision time and automobile availability) and policy-oriented variables (eg out-of-vehicle time and frequency of service) that are new to mode choice research.

TRANSPORT ROUTE LOCATION: A THEORETICAL FRAMEWORK.

Abstract A theoretical framework for explaining the historical placement of a transport route through a distribution of places based on economic considerations is proposed. Following the statement of certain necessary assumptions, the paper graphically illustrates the placement of routes for two and three nodes, and for three nodes with construction subsidies. A discussion of the four-node case follows this. Because of the combinatorial nature of the problem addressed, the graphical approach is replaced by a shortest-path algorithm, which searches a profit space based on link potential for profitable routes. Three different historical route location problems are analysed using the framework proposed here. In each case the approach locates routes that are clearly within the geographic limits of profitability. The success of the approach in replicating the three cases examined suggests that it merits further testing and refinement.

A note on the use of correlation coefficients for assessing goodness-of-fit in spatial interaction models

The use of correlation coefficients to evaluate the accuracy of spatial interaction models is inappropriate unless such models have been fitted using least squares techniques. In other cases the correlation involves an implicit intercept value and a regression coefficient that may significantly modify the interaction models estimates. Researchers have not acknowledged the role of these two parameters when the correlation is used. A generalized root mean square error is proposed as an alternative indicator of accuracy that may be used with any model.

Research Commentary: Increasing the Flexibility of Legacy Systems

Flexibility is what people seek when striving to increase or expand economic and social choices, equity, and technological innovations. Flexibility provides the robustness needed to adjust to changes such as those arising from a warmer/colder world, and the actions required when managing threats from and results of social strife, economic downturns, environmental catastrophes, infrastructure disruptions, and war. Flexibility is easy to praise at the level of principle, if allowed that a bit of stability and resistance to change does have merit. At the level of practice or operations the concept is most illusive, and explaining what flexibility means, why it is thwarted, and how it might be obtained is a challenging task. This paper begins by contrasting views of systems and their behaviors. Alternative explanations for behaviors thwarting flexibility are identified. Consequences of inflexible, locked-in development paths are illustrated using examples from transportation and similar systems. Suggestions for increasing flexibility are made after examining system behaviors in dynamic contexts. Academic, government, and industry experiences inform and color interpretations.