Gantry crane operations to transfer containers between trains: A simulation study of a Spanish terminal

Freight transfer operations are critical in combined transport networks. In this paper a simulation model and modelling approach to the transfer of cargo between trains at rail terminals is presented. The model is used to study the Port-Bou terminal, the main intermodal terminal at the Spanish-French frontier. Four different gantry crane operation modes to interchange containers between trains are evaluated. These operation rules are tested in several scenarios to examine the critical factors of the system and the best operation rule for each situation. Latest generation software is used to develop the model that incorporates modular programming and enhanced graphic systems for output representation. It allows a dynamic display of the simulated system and, likewise, the possibility of developing modules that can be reused in other studies. The research shows how simulation can be a useful planning tool in the rail transportation context.     

Public vs private management of public utilities - The case of urban public transport in Europe

This paper analyses the determinants of the performance differential between the private and public management of urban public transport in Europe. Our analysis supports the view that private management is associated with a lower operating cost. We show, however, that the size of the costs' differential can depend on the interaction of the local authorities' capacity for expertise and the private operators' autonomy margin. In particular, we show that, in certain situations, there might be little difference in operating costs. Thus, in terms of total costs (production and transaction costs), no systematic advantages should be expected from private management.     

A study of the response of chlorophyll-a biomass to a winter upwelling event off Western Iberia using SeaWiFS and in situ data

Observations of a winter upwelling event off Western Iberia shelf/slope in the area of influence of the Western Iberia Buoyant Plume (WIBP) were conducted in February 2000. Spatial patterns and time evolution of the chlorophyll-a (chl-a) biomass are analysed, based on in situ and satellite data. SeaWiFS-derived chl-a concentration L2 products were used to track the chlorophyll front and estimate its westward migration velocity (maximum up to 29 km day⁻¹), as well as to characterize the frontal system and its evolution. A method associating the type of spectral signature of a pixel to the fraction of chlorophyll probed by SeaWiFS enabled the estimation of the chl-a biomass within error intervals. High chlorophyll concentrations (for wintertime) were observed over the shelf and slope, up to large distances to the coast. Due to the WIBP, a shallow Ekman layer developed, being nearly coincident with the stratified upper meters. The transport comprised westward advection and stretching of the plume, with little entrainment with the offshore deep mixed layer waters. The relative enlargement of the total area of the Inside-Front Zone (IFZ) during the upwelling event was roughly accompanied by the maintenance of the average biomass per unit of area, considering the water column up to depths of interest. This suggests that there was a net increase of chl-a biomass inside the water column associated with the IFZ, roughly proportional to the increase in the IFZ area. Retention of phytoplankton in the shallow stratified nutrient-rich waters of the WIBP was a key factor for this increase in chl-a biomass.     

Accompanied versus Unaccompanied Transport in Short Sea Shipping between Spain and Italy: An Analysis from Transport Road Firms Perspective

Short sea shipping (SSS) is called to play a key role in ensuring sustainable mobility in the European context. In the past years several studies tried to define the SSS requirements and also to identify the SSS lines that were economically viable. However, no studies approach the profile of their users—the road transport firms—and the organizational patterns adopted by them, in order to gain a better understanding of this transport modality. This research, on the basis of a sample of 81 international road transport firms that use SSS between Spain and Italy, analyses the profile of these firms and certain elements inherent to their relationship with the shipping firms, according to the two modalities of organizing their SSS transport operations: accompanied versus unaccompanied.     

The regulatory function in public-private partnerships for the provision of transport infrastructure

A wide range of contractual arrangements are increasingly being used by the public sector to materialise the delegation of transport infrastructure provision tasks to the private sector, over long periods of time. This paper addresses the issue of transport infrastructure regulation in the specific context of public-private settings. Starting by the discussion on the concept of Public-Private Partnership (PPP) it is stressed that, despite the different meanings that can be found in the literature, it is possible to define a PPP by using a core group of characteristics, such as the bundling of services and the transference of a relevant part of the risks to the private sector on a long term basis. Regarding the action of the regulator, we look at three dimensions of efficiency that are expected to be pursued at the strategic level of regulatory action. However, it is acknowledged that the regulatory function is in practice rather complex since it requires balancing a multiplicity of other objectives or goals, which may vary according to specific economic conditions. In the domain of pricing, the review carried out suggests that since “first best” assumptions are not met in the “real world” it hardly seems possible that the short run marginal cost pricing “canon” could be directly used to shape pricing policies. Consequently, when considering the application of the standard neoclassical marginal cost pricing approach it is pertinent to ask whether the second best solutions can lead to efficient outcomes that might be accepted by the stakeholders. Bundling construction and maintenance tasks into a single long term contract, which is a typical characteristic of “standard” PPPs, could theoretically bring cost benefits since it allows for the possible internalization of any positive externalities that may be generated during the whole project life cycle. The economic rationale for the bundling of construction/maintenance with financing services is that it enhances the likelihood of submission of realistic bids at the procurement stage. In addition, the chances of the contractor sticking to the agreed contractual terms, after contract award, are potentially increased given the higher exposure to financial risk.     

Residual circulation and sediment distribution in the Ria de Aveiro lagoon, Portugal

A two-dimensional hydrodynamic and sediment transport models have been developed and applied to the Ria de Aveiro lagoon, Portugal. The application consisted in the study of the residual circulation, the residence time as well as the sediment dynamics in the lagoon. High residence time for particles situated at the far end of the main channels points out that they are retained for a long time and tend to remain there, with high probability of being deposited into the bed. Low residence time for the central areas implies that the particles are flushed out more rapidly toward the lagoon mouth, revealing that the water and the particles exchange are very effective there. Although the residual circulation due to the rivers induces an overall transport toward the lagoon mouth, the residual circulations due to the winds induce particular circulation patterns (clockwise or counter-clockwise eddies) at some locations of the lagoon, depending on the wind direction. It was found that the suspended sediment concentrations along the main channels are induced by tidal asymmetries (resulting in areas of ebb and flood dominance), as well as by the wind stress and rivers runoff effects. They contribute, in general, to increase the sediment export toward the ocean, although the wind stress may induce currents and circulations in the opposite direction of the tidal currents. High turbid zones are observed for strong tidal currents, associated with tidal asymmetries, as well as with high rivers runoff. The erosion–deposition budget indicates a tendency for sediment accumulation at important areas of the lagoon, namely the shallow ones.     

Congestion and emissions mitigation: A comparison of capacity,demand, and vehicle based strategies

Capacity, demand, and vehicle based emissions reduction strategies are compared for several pollutants employing aggregate US congestion and vehicle fleet condition data. We find that congestion mitigation does not inevitably lead to reduced emissions; the net effect of mitigation depends on the balance of induced travel demand and increased vehicle efficiency that in turn depend on the pollutant, congestion level, and fleet composition. In the long run, capacity-based congestion improvements within certain speed intervals can reasonably be expected to increase emissions of CO₂e, CO, and NO_x through increased vehicle travel volume. Better opportunities for emissions reductions exist for HC and PM_2.5 emissions, and on more heavily congested arterials. Advanced-efficiency vehicles with emissions rates that are less sensitive to congestion than conventional vehicles generate less emissions co-benefits from congestion mitigation.     

Lightweight Occupancy Estimation on Freeways Using Extended Floating Car Data

Advanced traffic management systems rely heavily on technology to perform accurate estimations of the current state of the traffic as well as its short-term evolution. The objectives are improving traffic flow and enhancing road safety. Their success is based on accurate monitoring of two key variables, specifically speed and occupancy. The latter of the two has, to date, received significantly less attention from the scientific community. In this work we present a lightweight method to perform “on-line” occupancy estimation. We first propose three occupancy measurements calculated from data collected by a floating car: vehicle count, percentage of stop time, and headway. We then extend these discrete values to a continuous estimation of occupancy in space and time. The proposed estimators are based on a pairwise linear regression of each of the previously calculated measurements over certain references obtained from other floating cars or magnetic loop detectors. The method has been calibrated and validated under real traffic conditions and data. Despite the ease of implementation, the method is able to reproduce the occupancy values generated by the actual loop detectors, achieving promising results, with estimation errors down to 6.52%, even before multivehicle systems are considered.     

PPPs — True Financial Costs and Hidden Returns

The cost of using private finance is at the centre of the public private partnerships (PPPs) debate, but until now most works considered only the direct financial costs such as the loan interest rate and the shareholders return on equity and were based on various secondary sources. This paper focuses on seven shadow toll deals closed in Portugal between 1999 and 2002 and reports the financial costs of the PPP model considering also the associated transaction costs and is based on detailed information included in each concession's financial base case. The transaction costs include financial costs such as banking fees, due diligence costs and the impact of all cash distribution traps, such as reserve accounts or minimum-level of debt ratios. The PPP financial costs were then compared with the costs arising from raising public debt through a government or a public agency bond. Our analysis shows that the PPP ‘true' financing costs are, on average, 370 basis points above the cost of raising public debt and that the ‘transaction costs' account for around 40% of that financial premium.     

Comparative performance of alternative humanitarian logistic structures after the Port-au-Prince earthquake: ACEs,PIEs, and CANs

The paper analyzes the performance of different post-disaster humanitarian logistic structures that arose in response to the Port-au-Prince earthquake of January 12th, 2010. Based on field work conducted by the authors, the paper defines a typology of structures; assesses their relative performance in terms of delivering relief aid; and identifies the causes that explain the differences between them. Three structures are defined for comparative purposes: Agency Centric Efforts (ACEs), Partially Integrated Efforts (PIEs), and Collaborative Aid Networks (CANs). These structures differ to the extent to which they are integrated with the local social networks during the relief effort. Representative examples were analyzed to illustrate their inherent strengths and weaknesses, and reach conclusions of general applicability. The authors strengthen the analyses with discussions of “comparables,” i.e., other cases not fully discussed in the paper that shed additional light onto the performance of the structures.The paper’s analyses are based on dozens of interviews, both formal and informal, conducted with individuals directly involved in the relief effort, complemented with critical analyses of news accounts, and reports produced by the agencies involved. Based on its chief findings, the paper makes policy recommendations to maximize the effectiveness of future relief distribution efforts in response to disasters of various sizes.