Urban transportation modeling: The discussion continues

This article is a response to John Polak's article, entitled, A Comment on Supernak's Critique of Transport Modeling, published elsewhere in this issue of TRANSPORTATION. It offers necessary clarifications to the issues discussed in an earlier article in this journal (Supernak, 1983). It also responds to the philosophical issues discussed in Polak's article, such as the nature of transport phenomena, and the role, form and methodology of transport modeling.     

Transportation modeling: Lessons from the past and tasks for the future

In spite of the recent progress made in household activity analysis and travel budget studies, urban transportation modeling still remains a “not-too-well developed” research field. There are conflicting theories, analysis units are not uniform, terms are not precisely defined, basic studies of sub-systems involved are not yet completed, and many models lack behavioral background as well as basic attributes such as simplicity, sensitivity, compatibility, transferability and forecasting ability. Gaps in methodology may be partially responsible for this situation. There is an urgent need for simple, yet not primitive, easily applicable urban transportation models which can respond to the technical needs of planners and engineers. Lessons from the past, as well as experiences from other disciplines, suggest that future research should concentrate on: (1) new, “unconventional” approaches based on systematic, basic studies of all sub-systems involved; (2) proper definition and stratification of an analysis unit; (3) revision and unification of definitions, classifications, etc., in order to improve the behavioral background of the models; (4) dynamic rather than static approaches, able to describe feedbacks between transportation and land-use as well as between transportation demand and supply; (5) interrelations between subsequent sub-models, particularly between car availability, trip generation and modal split; (6) developing models which are not only sensitive to transportation policies but also to other local policies (e.g. land use, city development, social, etc.).     

The privatization of Polish ports—the present situation and outlook for the future

The Polish economy is going through fundamental changes from a central planning to a market economy. The main aim of this transition is the privatization process which has to change the structure of Polish economy. Privatization has to establish more favourable ways of utilizing the productive capacity of state enterprises and create better conditions to compete on the market. The Privatization process for Polish state enterprises was defined in the Act on the Privatization of State Enterprises of 13 July 1990. According to this Act state enterprises can be privatized in capital or liquidation methods. The capital method has been applied to the privatization of Polish ports. In 1991 the major Polish ports were transformed into a State Treasury shareholder company. The holding company was used in the first stage of privatization. Gdynia was the first port which started this process building the real model of holding. Another important element connected with the structural transformation of Polish ports is the separation of operational and management roles. According to the Act on Ports, the Port Authority is also responsible for the development of the commercial, industrial and distribution services. This Act will also enable Poland to adapt economic and legal regulations which are similar to those in the European Union ports.     

Towards safety improvement: implementation and assessment of new standards of competence for Electro-Technical Officers on ships

The paper deals with education of ship engineers as an integral part of maritime policy in global shipping. The central problem, how to reconcile technological advancement with training en route to improving safety, is defined. A complete conceptual model for solving a central question is formulated and described. At the beginning, a short analysis of technological advances and the need for training is presented. Next, the basic components of conceptual model, including implementation and assessment of new standards of competences for Electro-Technical Officers in the wake of Maritime Education and Training (MET) development are discussed. A key point of the assessment procedure is focused on the formulation of criterion defining the impact of new standards on the given processes characterizing a professional carrier development of seafarers. These processes, which mean certification process and recruitment of candidates to seafarer profession, are strongly linked with and influenced on MET development and improving the safety of shipping. Empirical application by pointing the Polish case study to the framework of conceptual model under consideration is shown and analysed. Finally, the future works as well as the concluding remarks are formulated and commented on.     

The privatization of Polish ports—the present situation and outlook for the future

The Polish economy is going through fundamental changes from a central planning to a market economy. The main aim of this transition is the privatization process which has to change the structure of Polish economy. Privatization has to establish more favourable ways of utilizing the productive capacity of state enterprises and create better conditions to compete on the market. The Privatization process for Polish state enterprises was defined in the Act on the Privatization of State Enterprises of 13 July 1990. According to this Act state enterprises can be privatized in capital or liquidation methods. The capital method has been applied to the privatization of Polish ports. In 1991 the major Polish ports were transformed into a State Treasury shareholder company. The holding company was used in the first stage of privatization. Gdynia was the first port which started this process building the real model of holding. Another important element connected with the structural transformation of Polish ports is the separation of operational and management roles. According to the Act on Ports, the Port Authority is also responsible for the development of the commercial, industrial and distribution services. This Act will also enable Poland to adapt economic and legal regulations which are similar to those in the European Union ports.     

Material transport from the nearshore to the basinal environment in the southern Baltic Sea: I. Processes and mass estimates

Processes involved in erosion, transport and deposition of cohesive materials are studied in a transect from shallow (16 m) to deep (47 m) water of the SW Baltic Sea. The wave- and current-induced energy input to the seabed in shallow water is high with strong variability and suspended matter concentrations may double within a few hours. Primary settling fluxes (from sedimentation traps) are less than 10 g m⁻² day⁻¹, whereas resuspension fluxes (evaluated from sedimentation flux gradients) are 15–20 times higher and the residence time for suspended matter in the water column is 1–2 days. Settling velocities of aggregates are on average six times higher than for individual particles resulting in an enhanced downward transport of organic matter. Wave-induced resuspension (four to six times per month) takes place with higher shear stresses on the bottom than current-induced resuspension (three to five times per month). The short residence time in the water column and the frequent resuspension events provide a fast operating benthic–pelagic coupling. Due to the high-energy input, the shallow water areas are nondepositional on time scales longer than 1–2 weeks. The sediment is sand partly covered by a thin fluff layer during low-energy periods. The presence of the fluff layer keeps the resuspension threshold very low (<0.023 N m⁻²) throughout the year. Evaluated from 3-D sediment transport modeling, transport from shallow to deep water is episodic. The net main directions are towards the Arkona Basin (5.5×10⁵ t per year) and the Bornholm Basin (3.7×10⁵ t per year). Energy input to the bottom in deep water is low and takes place much less frequently. Wave-induced resuspension occurs on average once per month. Residence time of particles (based on radioactive isotopes) in the water column is half a year and the sediment accumulation rate is 2.2 mm year⁻¹ in the Arkona Basin.     

Application of inductive loops as wheel detectors

This article presents the findings of model and field research into narrow inductive loop used as vehicle wheels detector in normal traffic conditions. The efficiency of the solution was compared with that of strip, polymeric piezoelectric detectors. The findings confirmed that narrow inductive loops can be successfully applied as wheel detectors.