Environment and Planning B: Urban Analytics and City Science

Public transit service is a promising travel mode because of its potential to address urban sustainability. However, current ridership of public transit is very low in most urban regions—particularly those in the United States. Low transit ridership can be attributed to many factors, among which poor service quality is key. Transit service quality may potentially be improved by decreasing the number of service stops, but this would be likely to reduce access coverage. Improving transit service quality while maintaining adequate access coverage is a challenge facing public transit agencies. In this paper we propose a multiple-route, maximal covering/shortest-path model to address the trade-off between public transit service quality and access coverage in an established bus-based transit system. The model is applied to routes in Columbus, Ohio. Results show that it is possible to improve transit service quality by eliminating redundant or underutilized service stops.

The authors discuss recent progress in extracting road networks from digital imagery. We briefly review recent developments in methods for the automatic extraction of road centre line networks and propose a related algorithm aimed at encoding the geometry of road networks with line segments. Our algorithm is inspired by ‘axial lines’, which have been defined as lines of uninterrupted movement within urban streetscapes or buildings. We show that axial lines appear as ridges in isovist fields. These are formed from the maximum diametric lengths of the individual isovists, sometimes called viewsheds, which make up these fields. We present an image-processing technique for the identification of lines from ridges, discuss current strengths and weaknesses of the method, and show how it can be implemented easily and effectively.

A fractal environment can accommodate more small objects than expected because fresh small spaces come into play as the size of object diminishes. Could the built environment behave like this? To test this hypothesis the number of cars that could be parked in a street was estimated for different sizes of car. The results indicated that scaling does occur. This is as if space can be manufactured from nothing by designing at an appropriate scale. Countries such as Japan which have a small standard of personal space may in fact be larger than they seem on a map.

Much geographic information is an interpretation of reality and it is possible for multiple interpretations to coexist. This is unproblematic for the research community but, as the numbers of users increase through initiatives resulting in data integration on an unprecedented scale, such as E-science and GRID, issues of information meaning and conceptualisation become more important. We explore these issues through the mapping of land cover and the variety of conceptions of land-cover features that may be held by actors in the creation, distribution, and use of the information. Current metadata do not report the wider meaning of the information categories in terms of the decisions that were made and by whom in specifying class conceptualisations.

This paper gives a technique to extrapolate the anticipated accuracy of a prediction of land-use and land-cover change (LUCC) to any point in the future. The method calibrates a LUCC model with information from the past in order to simulate a map of the present, so that it can compute an objective measure of validation with empirical data. Then it uses that observed measurement of predictive accuracy to anticipate how accurately the model will predict a future landscape. The technique assumes that the accuracy of the model will decay to randomness as the model predicts farther into the future and estimates how fast the decay in accuracy will occur based on prior model performance. Results are presented graphically in terms of percentage of pixels classified correctly so that nonexperts can interpret the accuracy visually. The percentage correct is budgeted by three components: agreement due to chance, agreement due to the predicted quantity of each land category, and agreement due to the predicted location of each land category. The percentage error is budgeted by two components: disagreement due to the predicted location of each land category and disagreement due to the predicted quantity of each land category. Therefore, model users can see the sources of the accuracy and error of the model. The entire analysis is computable for multiple resolutions, so users can see how the results are sensitive to changes in scale. We illustrate the method with an application of the land-use change model Geomod to Central Massachusetts, where the predictive accuracy of the model decays to 90% over fourteen years and to near complete randomness over 200 years.

The authors build on a recent development in urban geographic theory, providing evidence of an oscillatory behavior in spatiotemporal patterns of urban growth. With the aid of remotely sensed data, the spatial extent of urban areas in the Houston (USA) metropolitan region from 1974 to 2002 was analyzed by spatial metrics. Regularities in the spatial urban growth pattern were identified with temporal periods as short as thirty years by means of spatial metric values, including mean nearest-neighbor distance, mean patch area, total number of urban patches, and mean patch fractal dimension. Through changes in these values, a distinct oscillation between phases of diffusion and coalescence in urban growth was revealed. The results suggest that the hypothesized process of diffusion and coalescence may occur over shorter time periods than previously thought, and that the patterns are readily observable in real-world systems.

This paper presents an urban land-use simulation model using cellular automata (CA). In the model urban growth is regarded as the result of a global process underpinned by local actions and land-use change as the joint action of three different effects: attribute, heterogeneity, and gravity. The attribute and heterogeneity effects are regarded as different aspects of a local driving force for change constituted by changing accessibility and other attributes resulting from the interaction of land use and transport at the neighborhood level. The gravity effect is a universal resistance to change as a result of inertia and agglomeration of compatible land uses in the vicinity. To ensure that local actions would lead to global behavior, a multipass, in addition to a single-pass, land-use-allocation algorithm is designed to mimic land-use changes. With metropolitan Melbourne in Australia as a case study, the performance of the model in replicating land-use changes is compared with that of an alternative model developed by using only a distance function. The results of the comparison show that the proposed CA model outperforms the alternative model with only a distance function, confirming the importance of incorporating local attributes in modeling land-use changes.

Empirical research in the built environment field is hampered by a lack of reliable measurement tools. The authors argue that there is a need for measures of built form that are objective, descriptive, comprehensive, reliable, practical, and address all environmental scales. They outline the development of an instrument to measure physical characteristics of housing for use in a study funded by the Wellcome Trust, on the effects of regeneration on mental health. The Built Environment Site Survey Checklist (BESSC) contains a wide range of items designed to be rated by built environment specialists for individual predetermined ‘housing areas’. The interrater reliability of the BESSC was tested using the κ and weighted κ statistics for categorical variables and item rankings and intraclass correlation coefficients for continuous measures. The majority of the items were found to be reliable and, although the instrument requires further refinement, it offers substantial potential for investigation of the relative merits of alternative urban forms and the generation of research-based design guidance.

The Ricardian principle of comparative advantage is used frequently as a foundation for illustrating potential improvements in the allocation of production and trade flows among countries. Such improvements typically consist of increased economic efficiency in the form of lower aggregate production costs and greater welfare in the form of higher levels of aggregate output. The improvements are made possible by the effective integration of otherwise individual economies. This paper employs the principle of comparative advantage as the foundation for illustrating potential improvements in the allocation of land uses under a regional approach to land-use planning. It uses a generalized assignment problem within a geographical information system (GIS) to describe the efficiency benefits of integrating land-use plans among several districts.

Research has shown that views are an important factor in the overall satisfaction of building occupants, but, because they are qualitative and subjective, views are difficult to assess. This paper presents a new approach to analyzing views using a fuzzy logic methodology, with the aim of assessing the amenity of views. It illustrates the process of constructing a system from data collection and fuzzy rules design, to inference and defuzzification procedures. With the verification of the prediction outcomes, it is shown that the evaluation model can successfully mimic a human's subjective preferences for scenic views. The methodologies and the underlying principles of the evaluation model are explained.