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- Andersson, Matts, et al.
(author)
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A method for measuring and valuing transport time variability in logistics and cost benefit analysis
- 2017
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In: Research in Transportation Economics. - : Elsevier. - 0739-8859 .- 1875-7979. ; 66, s. 59-69
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Journal article (peer-reviewed)abstract
- The freight transport system is subject to delays and disturbances, which influence investment and planning decisions made by governments and infrastructure authorities. Traditionally relying on Cost Benefit Analysis (CBA) they are dependent on correct and up-to-date input data. So far, little success has been reached in estimating the effects of disturbances for freight. This paper aims to contribute to the understanding of disturbances in freight transport by reviewing and classifying the effects occurring due to transport time variability (TTV) and to suggest a calculation model to estimate the value of transport time variability (VTTV). In order to validate the model and its usability it was successfully tested in a case study for a large Swedish retail company. The effects of delays can be divided into four main types: System Killers, Catastrophic Events, Expected Risks, and Contingencies, of which the last two are relevant for VTTV. The model applies these in a two-step cost function with a fixed and variable part, building on previous studies of VTW for passenger transport based on the scheduling utility approach. A main theoretical result is that the estimation of VTTV is derived mathematically independently of which measure that is chosen for the quantification of TTV.
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| 2. |
- Andersson, Matts, et al.
(author)
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A method for measuring and valuing transport time variability in logistics and cost benefit analysis
- 2016
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In: World Conference on Transport Research, WCTR 2016, Shanghai 10-15 July.
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Conference paper (other academic/artistic)abstract
- Today transport system is subject to delays and disturbances, which has impacts on the transport chain itself and on the recipients of the goods. These effects influence the investment and planning decisions made by governments and infrastructure authorities. These authorities traditionally rely on Cost Benefit Analysis (CBA) as an input to their decisions. By performing CBA calculations they can base their decisions on a solid and comparable foundation. However, CBA is dependent on correct and up-to-date input data, but little success has been reached in determining the effects of disturbances. Largely, this is due to the complex and context depend nature of disturbances and thereby obvious difficulties in estimating the effects. This paper aims to contribute to the understanding of disturbances in freight transport by reviewing and classifying the effects occurring due to transport time variability (TTV) and to suggest a calculation model to mathematically estimate the value of transport time variability (VTTV). The calculation method is tested in a case study for a large Swedish retail company. An extensive literature review has been performed on the existing methods to measure TTV and VTTV. Except identifying the measures used in the studies, any discussions in the studies on which measure to use has also been analysed. Effects of delays are further analysed and mapped in an activity framework of Transport, Transhipment, Delivery, Use of goods and Overall chain effects. Based on this mapping, four main types of disturbances are identified based on Magnitude and Frequency, followed by a suggestion on how these disturbances should be managed in a VTTV perspective. A method has also been developed to mathematically estimate VTTV for freight, extending previous studies on VTTV for passenger transport based on the scheduling utility approach and linked to the previous defined framework of four main types of disturbances. The study has resulted in an improved understanding of the effects of disturbances in freight transport networks through the developed framework. Further, a mathematical method for estimating VTTV has been developed. The model contains is a two-step cost function with a fixed and variable part. The method have successfully been tested on a test data set and proven to be able to estimate VTTV. Furthermore, this study has found that the estimation of VTTV can be (and is) derived mathematically independently of which measure that is chosen for the quantification of TTV.
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| 3. |
- Landergren, Magnus, 1988-, et al.
(author)
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VTTV – Value of Transport Time Variability : Method development and synthesis. Value transfer, measurements, and decomposition of VTTV
- 2015
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Reports (peer-reviewed)abstract
- Transporttidsvinster (TTS) och minskad transporttidsvariation (TTV) för gods-och passagerartrafik är viktiga nyttoposter i de samhällsekonomiska kalkylerna inom transportsektorn. Ett av antagandena som behöver göras är den monetära värderingen av TTS och TTV – VTTS och VTTV. Resenärers värderingar av dessa mått baseras oftastpå SP-studier (Stated Preference). VTTS för godstrafik baseras på kostnaden för kapitalbindningen i, och därmed värdet av, godset. I nuläget antas VTTV vara lika med det dubbla VTTS. Transportörers nyttor av minskad transporttid och transporttidsvariation beräknas som en del av transportkostnaderna (i andra poster i kalkylen). Detta projekt fokuserar på VTTV för godstransporter.Den här rapporten består av två delar. Kapitel 2, som är skrivet av WSP, Handelshögskolan vid Göteborgs Universitet och Logistics Landscapers, beskriver WP 4 som handlar om vilket mått som ska användas för transporttidens variation, vilka delar VTTV består av samt härleder en matematisk modell för att beräkna VTTV.Syftet med WP 4 var ursprungligen att kartlägga och utvärdera olika mått för transporttidsvariationen (TTV). Med mått menas enheten som används för att kvantifiera variationen, som exempelvis standardavvikelsen eller den genomsnittliga förseningen. En litteraturstudie har genomförts där använda mått i 22 tidigare samhällsekonomiska studier i Sverige ochutomlands listas. En slutsats av litteraturstudien är att många olika mått använts, vilka kan kategoriseras underStandardavvikelseSpridning (ofta i form av skillnad mellan percentiler)Andel av sändningar som är försenadeGenomsnittlig försening (om försenad)Fördelar och nackdelar med de olika måtten diskuteras. En annan slutsats är att valet av mått sällan diskuteras i de genomgångna studierna, utan man verkar ha valt ett mått som passar undersökningsmetoden. Vidare har det undersökts om det används mått inom logistikbranschen som skulle kunna passa TTV inom samhällsekonomin. Slutsatsen är att dessa mått (eller indikatorer) är framtagna med andra syften och för användning på mikronivå (företag eller enskilda transportkedjor) vilket gör det svårt att tillämpa dem på makronivå. Dock finns ett behov av mått på en mesonivå som gör det möjligt att analysera förändringar i transportsystemet ur båda perspektiv – samhällets och enskilda aktörers.
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| 6. |
- Bengtsson, Magnus, Docent, et al.
(author)
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A proposed method using GPU based SDO to optimize retail warehouses
- 2022
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Conference paper (peer-reviewed)abstract
- Research in warehouse optimization has gotten increased attention in the last few years due to e-commerce. The warehouse contains a waste range of different products. Due to the nature of the individual order, it is challenging to plan the picking list to optimize the material flow in the process. There are also challenges in minimizing costs and increasing production capacity, and this complexity can be defined as a multidisciplinary optimization problem with an IDF nature. In recent years the use of parallel computing using GPGPUs has become increasingly popular due to the introduction of CUDA C and accompanying applications in, e.g., Python. In the case study at the company in the field of retail, a case study including a system design optimization (SDO) resulted in an increase in throughput with well over 20% just by clustering different categories and suggesting in which sequence the orders should be picked during a given time frame. The options provided by implementing a distributed high-performance computing network based on GPUs for subsystem optimization have shown to be fruitful in developing a functioning SDO for warehouse optimization. The toolchain can be used for designing new warehouses or evaluating and tuning existing ones.
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| 7. |
- Brehmer, Per-Olof, et al.
(author)
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Measuring performance in supply chains
- 2001
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In: World transport research : selected proceedings of the 9th World Conference on Transport Research, 22-27 July 2001, Seoul, Korea.
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Conference paper (peer-reviewed)
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