| 1. |
- Hörteborn, Axel, 1986, et al.
(författare)
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A comparison of two definitions of ship domain for analysing near ship–ship collisions
- 2020
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Ingår i: Proceedings of The 8th International Conference on Collision and Grounding of Ships (ICCGS8) - Developments in the Collision and Grounding of Ships and Offshore Structures. ; 2019, s. 308-316
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Konferensbidrag (refereegranskat)abstract
- This paper compares two definitions of ship domain (SD) for analysing near ship–ship collisions in order to assess the risk of such events. One of the SDs follows Fujii’s definition, which is based on a ship’s dimensions, whereas the other was calculated with data from the Automatic Information System (AIS) in selected traffic locations. Case study simulations of traffic situations at three ship crossing locations were conducted using a Vessel Conflict Ranking Operator model, the results of which were examined according to the two definitions and their suitability for analysing near ship–ship collisions. The SD defined according with AIS data identified more cases with low angles of intersection as near-misses than the SD based on Fujii, which identified more situations with larger angles and higher speeds. IWRAP calculations are presented for the three locations to illustrate the probability of ship–ship collisions.
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| 2. |
- Hörteborn, Axel, 1986, et al.
(författare)
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A revisit of the definition of the ship domain based on AIS analysis
- 2019
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Ingår i: Journal of Navigation. - 0373-4633 .- 1469-7785. ; 3:72, s. 777-794
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Tidskriftsartikel (refereegranskat)abstract
- When ships approach each other, they should keep a minimum area around them clear of other vessels in order to remain safe. The geometrical shape of this area has been studied since the early 1970s and is defined as the ship domain. The progress in computer capacity since then and the introduction of the Automatic Identification System (AIS) provides the potential to further investigate the size and the governing factors of the domain. This investigation revisits and proposes a method using data based on 600,000 ship encounters at 36 locations. It is concluded that the ship domain has the shape of an ellipse with half axis radii of 0.9 and 0.45 nautical miles. However, there are two factors that greatly affect the ship domain: how large the area is that is used to gather vessel intersections and whether they are constrained by water depth. In contradiction to some previous research, it is found that the ship domain is unrelated to the length of the ship.
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| 3. |
- Hörteborn, Axel, 1986
(författare)
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Allision modelling in IWRAP Mk II - A verification and sensitivity study
- 2024
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Ingår i: Advances in the Collision and Grounding of Ships and Offshore Structures - Proceedings of the 9th International Conference on Collision and Grounding of Ships and Offshore Structures, ICCGS 2023. ; , s. 51-58
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Konferensbidrag (refereegranskat)abstract
- Risk assessment is important both while planning to build new infrastructure and for maintenance of existing structures. The probability of ship-structure allisions could be estimated with IWRAP Mk II, which is a commonly used software for estimating maritime risks. However, the research coverage of the software is limited with regards to groundings and allisions. The aim of this study is to verify how IWRAP Mk II estimates the accident probability. To perform this verification a separate tool is constructed, OMRAT, based on the same theory as IWRAP Mk II. The aim is also to highlight the sensitivity of different parameters in these types of models. It is concluded that IWRAP Mk II estimates the probability of allisions and groundings with the same equations. Another conclusion is that some parameters have a linear effect on the accident probabilities and other parameters are also influenced by the model layout.
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| 4. |
- Hörteborn, Axel, 1986, et al.
(författare)
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Economic incentives and technological limitations govern environmental impact of LNG feeder vessels
- 2023
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 429
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Tidskriftsartikel (refereegranskat)abstract
- In the transition to sustainable shipping, Liquified Natural Gas (LNG), is proposed to play a role, reducing emissions of sulphur and nitrogen oxides, and particulate matter. However, LNG is a fossil fuel and there is an ongoing discussion regarding the extent of methane slip from ships operating on LNG, challenging the assumptions of LNG as a sustainable solution. Here we show another aspect to consider in the environmental assessment of shipping; LNG feeder vessels may spend as much as 25% of their time at sea just running the ship to ensure the pressure in the tanks are not exceeded, i.e., run time not directly attributed to the shipment of gas from one port or ship, to another. In other words, the economic incentives are currently allowing for roughly 32% increase of the ships’ operational emissions and discharges and increased navigational risks. Most coastal areas are heavily affected by anthropogenic activities and e.g., in the Baltic Sea there is consensus among the HELCOM member states that the input of nutrient and hazardous substances must be reduced. Even if the LNG feeder vessels are currently few, the possibility to reduce their environmental impact by 32% should be an attractive opportunity for future policy measures and investigation of technological solutions of the problem.
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| 5. |
- Hörteborn, Axel, 1986
(författare)
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Ship Behaviour and Ship Bridge Allision Analysis
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for maritime transport has increased with the growing demand for worldwide trade. This has led to a major increase in maritime traffic and ship sizes over the last decades, which raises the probability of accidents. The methods used in maritime risk assessments today are based on old hypotheses that do not include all data available today. The main objective of this thesis is to develop numerical models and methods for the analysis of what is considered as normal navigation behaviour at sea today and improve the analysis of probability for ship-bridge allisions. The first part of the thesis describes what is considered as normal meeting distance at sea today. This information is later used while identifying failure events to ensure that the event behaviour was not caused by other ships. These few cases are excluded from the methodology since the communication and situational awareness in the situations are not known. However, while studying the probability of ship-bridge accidents, it is also important to understand how waterway restrictions may affect the probability of ship-ship collisions. Therefore, this thesis also includes a study of how the improved knowledge concerning meeting distance could be used in a near ship-ship collision identification model. One of the main findings considering normal meeting distance is that small and large ships meet each other at a similar distance at sea. In the second part of the thesis, a methodology is proposed to estimate the probability of ship-bridge allision. The presented methodology uses Automatic Identification System (AIS) data and a ship manoeuvring simulator to simulate and analyse marine traffic with regards to risks for accidents, such as ship-bridge allisions. A failure event identification method is also presented, which is needed to determine the frequency, duration and behaviour for the accident scenarios. The three events that were modelled and simulated in the simulator were: drifting ship, sharp turning ship and missing turning point. The probability of the different failure events corresponded to previous statistics confirming the AIS-based methodology. This means the methods to obtain the probability and duration of the failure events could be utilised in other areas. The simulation methodology was confirmed with the probability of grounding in the Great Belt VTS area. This thesis firstly contributes to a better understanding of the modelling of probability for ship-bridge allisions. This will support bridge-building engineers who need to take into account accidental loads from ship-bridge allision while designing bridges. Secondly, this thesis also contributes to a better representation of normal behaviour at sea, which is used both in fairway designs and in estimations of ship-ship collisions.
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| 6. |
- Svanberg, Martin, 1982, et al.
(författare)
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AIS in maritime research
- 2019
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Ingår i: Marine Policy. - : Elsevier BV. - 0308-597X .- 1872-9460. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- Although not originally developed for research use, the Automatic Identification System (AIS) enables its data to be used in research. The present paper provides a structured overview of how AIS data is used for various research applications. Ten areas have been identified, spread across maritime, marine and other journals. Many stakeholders beyond the most frequently mentioned – authorities and maritime administrations – can benefit from the research in which AIS data is used. AIS data can be incorporated in various types of modelling approaches and play a small or large role as a source of data. AIS data can also be validated or used to validate research from other data sources. Although a large amount of AIS-based research adds to the literature, there is still a large potential for using AIS data for research by making greater use of the variety in AIS messages, combining AIS with other sources of data, and extending both spatial and temporal perspectives.
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