Aggregating mobile object trajectories: cumulative time geographic density estimation for GPS data

We present new approaches that expand upon the time geographic density estimation (TGDE) framework previously employed to estimate potential path trees. In the past, TGDE metrics have identified possible locations an individual moving object may have passed between, given known origin and destination points. This paper utilizes a new form of TGDE to investigate taxicab GPS traces over a specified time horizon with position ‘gaps’. To this end, we propose a new extension to the TGDE framework, TGDE-C, which is used to determine the cumulative TGDE values for a group of GPS traces, at a given location. These metrics are applied to multiple taxis and allow for time of day analysis. Additionally, we combine these new extensions with existing TGDE metrics that allow us to determine how accessible individual or groups of vehicles are to urban opportunities.     

Expertise in decision-making for large infrastructure projects: from UK trunk roads to High Speed Rail 2

At the decision-making stage, a large-scale infrastructure project is essentially a broad concept, and this means the expert analyses will differ from each other and become contested over time, leading to the emergence of rival narratives. It is only where there is a limited range of expert analyses that the bases for decision-making will remain relatively clear-cut. Over time the contested nature of expertise can significantly inhibit the construction of effective narratives, either for or against the project, and also make decision-making more complex and problematic. Decision makers may also seek greater clarification through the construction of narratives that rise above these disputed areas of expertise, and the scientific evidence becomes less important. This paper examines the changing nature of contested expertise through a comparative analysis of political decision-making between UK trunk roads policy and the case of High Speed Rail 2, through the framework of epistemic communities.     

Editorial Comment

This article examines fundamental questions concerning the origins and evolution of academic transport studies and the dynamics of its historical development. These fundamental questions are generally little discussed, yet are vital in gaining a better understanding of how the subject is driven forward. This article therefore attempts to answer these questions by taking the UK as a case study, with the principal method being evidence from semi-structured interviews with 20 senior figures integrally involved in the development of the subject. The characterization of transport studies provided by Allsop is employed as an analytical framework, enabling the construction of a historical narrative that can provide salient insights. Thus, it is argued that for academic transport studies the degree of early cross-fertilization with public arenas has meant that subsequent developments have been shaped by the subject's contextual environment. Most prominent among these developments has been the trend towards wider disciplinary breadth. This article examines the evolution of these processes, while the concluding section discusses their implications for consequent strengths and limitations of the subject.     

Automation of paratransit reservation,routing, and scheduling

Santa Clara County, California experienced a sharp growth in demand‐responsive paratransit ridership for individuals with disabilities, as a result of the passage of the 1990 Americans With Disabilities Act (ADA). This paper describes an automated paratransit system for the ADA‐type paratransit operation implemented in Santa Clara County. It automated paratransit reservation, scheduling, and routing functions. The key components of this system were a digital geographic database (DGD) and an automated trip scheduling system (ATSS). Empirical evidence after one year of operation indicates numerous benefits of this automation. There were significant reductions in the paratransit operating costs and an increase in the percent shared rides. The savings in operating costs far exceeded the annualized capital cost of automation. A user survey indicates that these improvements were achieved without degradation to service quality such as vehicle on‐time performance, invehicle travel times, vehicle response to open return, and ride comfort.     

Transit passenger response: Short and long term elasticities using time series analysis

This paper investigates the effects of price and service changes on transit ridership. The concept of elasticity is introduced and the traditional methods for estimating elasticities are discussed. In this paper an extra dimension is added by investigating short and long term elasticities. Time series analysis, developed by Box and Jenkins is chosen for the analysis. The Box and Jenkins methodology is applied to a monthly time series of average weekday ridership on the Chicago Transit Authority (CTA) rail system. Four categories of explanatory variables are investigated: fare on the CTA rail system, service provided on the CTA rail system, cost of car trips and weather effects. The effects of gas prices and rail service were found to be significant; however the results indicate a twelve month delay before service changes influence ridership. The effect of transit fares was found to be insignificant, indicating that both the short and long term fare elasticities are zero.     

Host specificity in copepod parasites of deep-sea fishes

Parasitic copepods belonging to two orders, Siphonostomatoida and Poecilostomatoida, are frequently reported from fish hosts in the deep sea. Three families of copepods are most commonly encountered, Sphyriidae, Lernaeopodidae and Chondracanthidae, but members of another four families, Hatschekiidae, Pennellidae, Philichthyidae and Hyponeoidae, are occasionally recorded. These parasites utilise various deep demersal fishes as hosts, especially species of the most abundant families, Macrouridae, Moridae, Synaphobranchidae and Alepocephalidae. Host specificity levels are variable, as for shallow-water fishes. In contrast, few parasites are regularly reported from fishes inhabiting the pelagic water column away from the bottom and away from the near-surface zone. Only the pennellids Sarcotretes scopeli and Cardiodectes medusaeus appear common on pelagic fishes, in the Atlantic and Pacific respectively. Host specificity levels in these two pennellid species are relatively low. It is speculated that the difficulty of encountering a host in the vast pelagic biome has restricted the diversity of parasitic copepods that have successfully colonized pelagic fishes.     

Tanzanian coastal and inland ports and shipping: crises and policy options

This paper explores the current state of coastal and inland shipping in Tanzania. It provides an overview of the state of ports and shipping in Tanzania, and the reasons underlying the present crisis of competitiveness in terms of both global pressures and national and regional dynamics. Problems of competitiveness are at least partially due to under-investment, management failures, skills shortfalls and difficulties in interfacing with the railway network. Less easy to resolve structural problems include the great imbalance between imports and exports, heightened regional competition and ongoing political instability in the Great Lakes region.     

My way or the highway? Framing transportation planners’ attitudes in negotiating professional expertise and public insight

Transportation planning continues to expand beyond traditional engineering and economic performance measures toward a broader scope of impacts across space and society. However, the attitudes of transportation planners as they balance their expert knowledge against public insights are not well-understood. We test a two-dimensional attitudinal framework using survey data from 311 U.S. and Canadian transportation planners. We reveal four attitudinal categories using principal component analysis, and hypothesis testing shows significant differences in personal and institutional attributes across these categories. We discuss what our results mean for training and regulatory measures striving to influence planner attitudes before proposing future directions for research.