| 11. |
- Abate, Megersa, 1980-
(författare)
-
Economic effects of air transport market liberalization in Africa
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Although the aviation industry is increasingly becoming important for Africa's economic development and integration, the ability of airlines to access foreign markets remains hindered by restrictive regulatory policies. Attempts have been made to fully liberalize the intra-African air transport market. Except for general assertions about the merits/demerits of liberalization, our empirical understanding of the welfare effects of such polices in Africa remains rudimentary. This study empirically measures the economic effects of air transport liberalization, mainly on two supply side variables: fare and service quality, measured as departure frequency. The results show up to 40 % increase in departure frequency in routes that experienced some type of liberalization compared to those governed by restrictive bilateral air service agreements. While the effect of liberalization is substantial in improving service quality, there is no evidence of its fare reducing effect.
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| 12. |
- Abate, Megersa, 1980-, et al.
(författare)
-
Joint econometric models of freight transport chain and shipment size choice
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In freight transportation, decisions regarding the choice of transport mode (or chains of modes) and shipment size are closely linked. Building on this basic insight, in this paper we estimate and review various joint econometric models using the Swedish National Commodity Flow surveys. Robust parameter estimates from this exercise will be used to update the current deterministic Swedish national freight model system (the SAMGODS model) to a stochastic one.
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| 13. |
- Abate, Megersa, et al.
(författare)
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The optimal shipment size and truck size choice : The allocation of trucks across hauls
- 2014
-
Ingår i: Transportation Research Part A. - : Elsevier BV. - 0965-8564 .- 1879-2375. ; 59, s. 262-277
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Tidskriftsartikel (refereegranskat)abstract
- There has been a growing interest in understanding how firms allocate their trucks across hauls, and how this allocation changes under various economic environments. This study investigates how variations in route/haul, carrier and vehicle characteristics affect the optimal vehicle size choice and the associated choice of shipment size. We show that the two choices are derived from the same optimization problem. There can be a continuum of shipment sizes, but decision-makers in freight transport have to choose from a limited number of vehicle alternatives. Therefore, we use a discrete-continuous econometric model where shipment size is modeled as a continuous variable, and vehicle size/type choice as a discrete variable. The results indicate that when faced with higher demand, and during longer trips firms are more likely to use heavier vehicles and ship in larger quantities which suggest that firms are realizing economies of scale and economies of distance. The study also discusses the effect of vehicle operating cost on the vehicle selection process and its policy implications.
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| 14. |
- Abbas, Khaled A, et al.
(författare)
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A generic approach for in depth statistical investigation of accident characteristics and causes
- 2001
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Ingår i: Proceedings of the conference Traffic Safety on Three Continents. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 653-665
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The main aim of this research is to develop a generic approach for the utilization of statistical methods to conduct depth investigation of road accident characteristics and causes. This approach is applied in an effort to analyse the 1998 accident database for the main rural roads in Egypt. This database is composed of traffic accident data collected for 14 road sections representing nine major roads of the Egyptian rural road network. The proposed approach is composed of two main stages of analysis. Within each stage, several analytical steps are conducted. The first stage is mainly concerned with developing cluster bar charts, where different characteristics and causes of accidents are portrayed in relation to variations in the three main accident contributing factors, namely types of roads, vehicles and drivers. The second stage is concerned with conducting in-depth statistical analysis of the collected accident data. Within this stage, four levels of statistical investigations were conducted. These are meant to examine a number of issues.
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| 15. |
- Abbas, Khaled A
(författare)
-
Environmentally sustainable transport strategies : the way forward in metropolitan cities
- 2001
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Ingår i: Proceedings of the conference Traffic Safety on Three Continents. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 780-791
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper is concerned with one of the three requirements of a sustainable transport system, namely the environmental dimension. It starts by presenting components and interactions of the transport and traffic systems using causal diagrams. Generic traffic problems are identified and their causes categorized. A classification of demand and supply-based policies and measures that can be used in designing environmentally sustainable transport strategies is depicted. Such strategies are targeted towards minimizing the generic traffic problems encountered in metropolitan cities, i.e., traffic congestion, accidents, environmental degradation and energy inefficiencies. In this paper, Travel Demand and Land Use Management are considered as two of the basic pillars for designing environmentally sustainable transport strategies. Criteria for comparing demand versus supply-based policies are suggested. These are applied to assess the benefits and limitations of each policy, hence assisting decision makers in the prioritization and choice of such policies.
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| 16. |
- Abdallah, Clement Kamil, et al.
(författare)
-
Assessing the quality of water used for vegetable irrigation in Tamale Metropolis, Ghana
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- This paper assesses water quality that is used for vegetable irrigation in Tamale Metropolis, Ghana. A mixed-method of research design was employed in this study to collect and analyze the data based on survey instruments. The paper found that Escherichia coli (E. coli) that is usually used as an indicator of water contamination and heavy metals exist in all taken water samples. The mean concentrations of nutrients such as ammonia, nitrate, nitrite and phosphate were recorded as 0.022 mg/l to 5.98 mg/l for ammonia, 1.06 mg/l to 7.52 mg/l for nitrate, 0.031 mg/l to 0.056 mg/l for nitrate and 0.037 mg/l to 0.069 mg/l for phosphate. E. coli and Total Coliforms levels for Sanghani, Kamina and Waterworks from the laboratory analysis were recorded as 3.2x10(3) CFU 100 m/l and 5.5x10(2) CFU 100 m/l, 4.0x10(3) CFU 100 m/l and 1x10(2) CFU 100 m/l, and 2.1x10(3) CFU 100 m/l and 4.6x10(2) CFU 100 m/l respectively. To conclude, based on the measured parameters, water used for irrigation in the Tamale Metropolitan is polluted and may cause potential health risks. Therefore, farmers, traders and consumers need to apply further safety measures to make the vegetables safe.
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| 17. |
- Abdel-Aty, M A, et al.
(författare)
-
Developing crash predictive models for a principal arterial
- 2000
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Ingår i: Proceedings of Traffic Safety on Two Continents. Conference in Malmö, Sweden, September 20-22, 1999. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 179-194
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Abdel-Aty, MA, et al.
(författare)
-
Using GIS to locate the high risk driver population
- 2000
-
Ingår i: Proceedings of Traffic Safety on Two Continents. Conference in Malmö, Sweden, September 20-22, 1999. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 111-126
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 19. |
- Abed, Ahmed, et al.
(författare)
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Uncertainty analysis of life cycle assessment of asphalt surfacings
- 2024
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Ingår i: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 25:2, s. 219-238
-
Tidskriftsartikel (refereegranskat)abstract
- The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data, deterministic solution, and asphalt durability. This framework was applied to six asphalt mixtures; the results show that there is significant uncertainty in the processes that contribute to the environmental impacts. They also showed that considering asphalt durability and its uncertainty is critical and can significantly change the results and interpretation of LCA.
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| 20. |
- Abenoza, Roberto F., et al.
(författare)
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What is the role of weather, built-environment and accessibility geographical characteristics in influencing travelers’ experience?
- 2019
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Ingår i: Transportation Research Part A. - : Elsevier Ltd. - 0965-8564 .- 1879-2375. ; 122, s. 34-50
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the effect of weather, accessibility and built-environment characteristics on overall travel experience as well as the experience with the latest trips. These are factors that are often disregarded in the travel satisfaction literature even though they are believed to largely influence the first mile of the door-to-door trip. This study fills a research gap in investigating all these factors by using, amongst other, a relatively large travel satisfaction survey from years 2009 to 2015 and by focusing on urban and peri-urban geographical contexts, the city and county of Stockholm (Sweden), respectively. The ordered logit model results show that county dwellers living close to a metro station and in well linked-to-all areas report higher overall travel satisfaction evaluations. In addition, precipitation and ground covered with snow have a negative influence on travel satisfaction. Our findings indicate that built-environment characteristics exert a rather weak influence on the travel experience, especially in the peri-urban context. However, some aspects such as living in areas with medium densities, low income and with high safety perceptions around public transport stations are associated with higher satisfaction levels. In turn, areas with single land uses are found to have lower travel satisfactions. These results are important for public transport planners and designers in devising measures to prevent and mitigate the negative outcome of some weather conditions and to conceive better designed transit oriented developments.
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