Using complex network theory to describe the relational geography of maritime networks has provided great insights regarding their hierarchy and evolution over the past two decades. Unlike applications in other transport fields, notably air transport, complex network theory has had limited application in studying the vulnerability of maritime networks. This study uses targeted link disruption to investigate the strategy specific vulnerability of the network. Although nodal infrastructure such as ports can render a network vulnerable as a result of labour strikes, trade embargoes or natural disasters, it is the shipping lines connecting the ports that are more probably disrupted, either from within the industry, or outside. In this paper we apply and evaluate two link-based disruption strategies on the global container shipping network, one based on link betweenness, and the other on link salience, to emulate the impact of large-scale service reconfiguration affecting priority links. The results show that the network is by and large robust to such reconfiguration. Meanwhile the flexibility of the network is reduced by both strategies, but to a greater degree by betweenness, resulting in a reduction of transshipment and dynamic rerouting potential amongst the busiest port regions. The results further show that the salience strategy is highly effective in reducing the commonality of shortest path sets, thereby diminishing opportunities for freight consolidation and scale economies.

Environmental Diversity (ED) has been proposed as a potential biodiversity surrogate for use in spatial biodiversity planning. The concept is based on the premise that differences in species composition between areas are correlated with differences in environmental conditions. If this is true then sites selected to represent the full range of environmental conditions in an area should provide good coverage of species diversity. This is potentially significant for conservation planning because environmental data are more easily available while species distribution data are often incomplete, but empirical tests of ED have been inconclusive. We explored the value of ED as a biodiversity surrogate using species distribution data from South Africa, focusing on how implementation affects its performance. We used empirical distribution datasets for birds, butterflies, frogs, and reptiles as well as artificial species distributions and modeled distributions for butterflies. Our results show that the form of the underlying optimization model and the number of environmental variables have a significant effect on the performance of ED while the choice of heuristic procedures for selecting sites has no significant effect. We conclude that ED can perform well as a biodiversity surrogacy strategy if it is implemented correctly.

a b s t r a c tTo address the underreporting of freight from a transport geography point of view, we present a novel analysis of the time and spatial characteristics of disaggregated commercial vehicle activities. The activities were extracted from raw global positioning system (GPS) data collected in South Africa over a sixmonth period for more than 30,000 commercial vehicles. The analyses of the activity chains provide useful characteristics such as activity and chain durations, number of activities per chain, and the spatial extent of the activity chains. Key results indicate that about 60% of activity chains have between 5 and 15 activities per chain while 25% of the chains have 4 or less; 89% of the chains have a duration of 24 hours or less; and approximately 75% of all activities start between 08:00 and 17:00. The paper's contribution is twofold: it firstly demonstrates a methodology to extract and evaluate vehicle activities and activity chains from raw GPS data. Novel results and characteristics about transport geographies in Gauteng, the economic centre of South Africa, are presented. We also report on the sensitivity of the analyses to certain parameters. Secondly, we introduce new metrics to evaluate a geographical area's economic productivity based on commercial activity.

The number of independent and interdependent freight actors (firms), the complex supply chain structures among them, and the sensitivity of shipment data are but a few reasons why modeling freight traffic is lagging its public and private transit counterparts. In this paper we used an agent-based approach to reconstruct commercial activity chains, and simulated them-along with private vehiclesfor a large-scale scenario in Gauteng, South Africa. The simulated activities are compared to the actual observed activities of 5196 vehicles that were inferred from GPS logs covering approximately six months. The results show that the activity chains reconstructed are both spatially and temporally accurate, especially in areas of high activity density. With freight vehicles being a major contributor to traffic congestion and emissions, our contribution is significant in bridging the gap between the person and commercial transport modeling state-of-the-art.

Telemetry devices are generating and transferring increasingly more data, with notable potential for decision makers. In this paper we consider the accelerometer and speed data produced by in-vehicle data recorders as a proxy for driver behaviour. Instead of extracting harsh events to cope with the large volumes of data, we discretise the data into a tractable and finite risk space. This novel methodology allows us to track both acceptable and non-acceptable driving behaviour, and calculate a more comprehensive risk model using the envelope of the data, and not a priori thresholds. We show how thresholds suggested in literature can characterise some driving behaviour as good, even though our empirical evidence has not even registered such extreme driving behaviour.We demonstrate the model using accelerometer data from 124 vehicles over a one month period. Three rules, each a combination of accelerometer and/or speed data, are applied to the risk space to derive person-specific scores that are comparable among the individuals. The results show that the scoring is useful to identify specific risk groups. The proposed model is also dynamic in that it dynamically adjusts to the observed records, instead of data having to abide by a limited model specification.

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The most essential and alluring characteristic of a security estate is the estate's ability to provide 24-hour security to its residents, of which the continual patrolling of roads and paths is vital. The objective of this paper is to address the lack of sufficient patrol route design procedures by presenting a tabu search algorithm capable of generating multiple patrol routes for an estate's security guards. The paper shows that the problem of designing these routes can be modelled as an Arc Routing Problem, specifically as min-max k postmen problems. The algorithm is illustrated with a real problem instance from an estate in Gauteng, South Africa. The patrol routes generated by the algorithm provide a significant improvement in the even patrolling of the road network, and a more balanced work distribution among guards. The algorithm is also tested on several benchmark problems from literature.

Paratransit provides a valuable service offering as a flexible and substitutional mode between formal transit and private car. When it evolves to compete with more formal transit modes, efforts are made to formalise it. As in many developing countries, the South African government generally views paratransit as a necessary nuisance, emerging and evolving in the absence of more formal transit services. Our paper aims to contribute by providing a more comprehensive context for the South African case: how specific Apartheid laws contributed to the formation of the mode and how deregulation provided a fertile ground for its exponential growth. The industry has evolved into an informal yet well-organised system that dominates the local transit market. Contrary to the popular view that the industry is an amorphous whole, this paper aims to create a more peoplecentred view of an industry that is made up of individuals trying to carve an existence in a harsh economic environment. We show how, if approached correctly, paratransit is more likely part of the land use and transport solution, and not a problem as it is often perceived to be.