| 1. |
- Abdi, Adel, et al.
(författare)
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Choice of Appropriate Tyres as an Asset to Traffic Safety on Winter Roads : Compilation and Evaluation of Some Winter Tyre Tests in Sweden
- 2011
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Ingår i: International Journal of Civil & Environmental Engineering. - 2077-1258 .- 2227-2763. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- Winter tyres must be able to cope with the slipperiness which occurs on the surface of the roads during winter. The slipperiness is generated by water vapour in the atmosphere, precipitating and transforming into a solid form i.e. in ice form, either directly or after refrigeration or cooling. Many experimental studies e.g. winter tyre tests have been carried out by many companies and authorities independently from each other to determine if there are any types of tyres which have the best grip on different road surface conditions in the winter. The purpose of this study is to compile, analyse, compare and evaluate the obtained results of some winter tyre tests which have been performed in Sweden during years 2007-2010. The study aims further to find out which types of these tyres are most appropriate as an asset and increase the traffic safety on Swedish winter roads. Both studded tyres and non-studded tyres, socalled friction tyres or all season tyres were used in the tests. The method of the study is partly based on a theoretical study by reviewing some literature in this area and furthermore studying some practical cases i.e. winter tyre tests. The results of the tests are given in tables and figures showing the function of different types of the studded and nonstudded tyres on different road conditions. All test-tyres have been supplied by several tyre manufacturers. The study is only limited to compare the grip and effectiveness of different type of winter tyres on different kind of road conditions. The study does not take the impact of the tyres on the environment into consideration. The study shows that currently there are several types of winter tyres on the market but there is no tyre that is ideal or works best under all winter conditions.
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| 2. |
- Abdi, Adel, et al.
(författare)
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Designing appropriate contracts for achieving efficient winter road and railway maintenance with high performance quality : A survey of the state of practice in Sweden
- 2014
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Ingår i: International Journal of Quality and Service Sciences. - 1756-669X .- 1756-6703. ; 6:4, s. 399-415
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - For a long time, the winter maintenance of the Swedish road and railway network had been performed in-house by Swedish Transport Administration, Swedish local authorities i.e. municipalities and Stockholm public transport. During the last 15 years the winter operation and maintenance of these state infrastructures have been performed by public procurement and contracting from independent contractors, where in practice the lowest price is the dominating selection criteria. The aim of this paper is to investigate and identify how these contracts are designed and how satisfied the parties are with the contract and the quality of the performed work during the winter and point our directions for improvement. Design/methodology/approach - The study was conducted by a literature review and followed by semi-structured interviews and electronic questionnaire. Findings - The results of the study which are based on the interviews and the online questionnaire show that there is widespread dissatisfaction with the contracts among both clients and contractors. Practical implications - The article prepares a basis showing how a contract affects the quality of the performed winter road and railway maintenance services. Originality/value - The findings lead to a number of suggestions about how to improve the contracts, e.g. having a separate winter maintenance contract to increase the quality of performed winter maintenance measures, a more partnering-like structure where consultations and adjustment can be made during the contract period. A partnering structure also makes it less important to get all the details right in the contract.
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| 3. |
- Abdi, Adel, et al.
(författare)
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Effective Winter Highway Maintenance through Applicationof Partnering Concept
- 2013
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Ingår i: International Journal of Engineering Management and Economics (IJEME). - 1756-5154 .- 1756-5162. ; 3:3, s. 112-125
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Tidskriftsartikel (refereegranskat)abstract
- Inmany countries winter road maintenance is outsourced to private contractors. Selecting appropriate contract for performance of winter highway maintenance and implementing it in an efficient way is then very important for both results and costs. Writing contracts concerning winter road maintenance is however difficult as weather conditions are hard to describe in an exact way and as what is rational to do in a certain situation, depends on expected future conditions. Problems during recent harsh winters in Sweden have clearly illustrated this. The study argues, with reference both to theoretical and empirical studies, that a partnering concept can improve efficiency in outsourced winter road maintenance. A detailed model of how partnering can be implemented is presented for winter road maintenance contracts together with systems for information supply such as International Roughness Index –surface unevenness measurement and Road Weather Information System.
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| 4. |
- Abdi, Adel
(författare)
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Efficient Winter Road Maintenance : A Study of Technical and Contractual Issues
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since ancient times, roads have tied people and cultures together. Roads have been createdwith the aim of facilitating trade and cultural exchange among different regions in the world. After the technologic development in vehicle industry and dramatically increase of motoring in the world during the past century road communication has gained a great importance for transporting people and goods. Thus, good safety and accessibility on roads all year round is now a vital necessity for a healthy economy in all modern societies. In order to keep roads safe, available for use with high transport quality they need to be maintained in real time. One of the most difficult tasks in this context is to keep the roads in good condition and accessible even during winter. The main objective of this doctoral thesis is to attempt to specify the most efficient ways of executing winter road maintenance. The preliminary issue in this context is whether it is the use of current assistive tools, that is, technical aspects that should be optimized and developed or whether it is the way in which winter maintenance services are procured and outsourced, that is, contractual aspects that should be improved which could give the optimal impact for both clients and contractors and make winter road maintenance more effective, or both issues. In order to define the outline of the research project a comprehensive state of the art survey was initiated with the intention of collecting and gaining insights into the earlier studies in the research area. Three basic areas associated with the performance of winter road maintenance were considered to be most relevant for review due to the anchorage between the areas. The selected areas were climatological, technical and contractual aspects. The literature review was followed by an electronic questionnaire survey. The results of the study in this stage showed that current technical methods almost functioned in a reasonable manner but there was an imprecise dissatisfaction with the current maintenance contract. The second stage of the research consisted of a number of additional empirical investigations in order to identify contractual problematic issues behind the current winter road maintenance in Sweden. Generally, those factors that are rarely considered as potential underlying causes to costly performance of winter road maintenance in Sweden were studied in this research project for example improper use of related technical assistive tools, procurement of improper bundled winter services and inappropriate contract structure. This thesis consists of six papers, five of which are related to each other, and the first one is completely independent but within research area. Findings in the thesis contributes to extend understanding about; how designing appropriate contracts can improve winter road maintenance, how proper use of assistive tools can reduce unnecessary winter road maintenance costs and minimize road traffic disruptions and delays, how a partnering structure in contracts can create confidence and trust between clients and contractors that in turn leads to minimizing or eliminating conflicts and disputes between parties involved, how choice of appropriate procurement methods through proper bundling of winter road services can contribute to shorten the procurement process and create incentives for contractors, and how selection of proper payment mechanisms can contribute to higher service quality of performed winter road measures. Additionally, an adequate knowledge and understanding of climate, proper knowledge of road weather and its impact on winter road traffic is essential for contribution of better planning of how to maintain the road network during winter. Since understanding about winter issues and its effect on winter road traffic is far from complete and winter road maintenance in the cold regions is a similar challenge, broad and complex, the results of this research may even contribute to improving winter maintenance problems in the countries with severe winters like Sweden.
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| 5. |
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| 6. |
- Abdi, Adel, et al.
(författare)
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Payment mechanisms for winter road maintenance services
- 2013
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Ingår i: Australasian Journal of Construction Economics and Building. - : University of Technology, Sydney (UTS). - 1835-6354. ; 13:4, s. 18-31
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Tidskriftsartikel (refereegranskat)abstract
- In countries with severe winters, a major portion of the annual budget for road maintenance is allocated to winter road maintenance. Thus it is important to identify an appropriate basis for the remuneration of the entrepreneurs who carry out the maintenance tasks, one that minimises or eliminates disputes and that satisfies both client organisations and contractors. The objective of this study is to investigate and evaluate the payment models applied in Sweden for winter road maintenance services and suggest possible improvements. Inadequate reimbursement models lead either to unnecessary cost overruns that affect the client's annual budget or cause cash flow problems for the contractor, which can result in safety issues. To solve the problems associated with paying for just-in-time road maintenance, cold region countries such as Sweden have developed various remuneration models, including some based on what is known as the Weather Index. The study uses a domestic questionnaire survey, analysis of a number of current contract documents, a series of meetings with project managers followed by an international benchmarking investigation. The study identified four winter maintenance remuneration models of which one is based on weather data. The study reveals that the payment model based on weather data statistics is applied only to roads with higher traffic flow and generates the most uncertainty about costs. Possible improvements should include more reliable weather data obtained from weather stations and bonuses related to customer satisfaction.
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| 7. |
- Abdi, Adel, et al.
(författare)
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Public Procurement of Winter Road Maintenance Services Based on EU Procurement Directive : Lessons from Sweden
- 2013
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Ingår i: Journal of Investment and Management. - : Science Publishing Group. - 2328-7721 .- 2328-7713. ; 2:4, s. 70-86
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Tidskriftsartikel (refereegranskat)abstract
- Public procurement of road maintenance services, particularly in cold regions is not an easy task in order to satisfy road-users during winter. Road-users’ dissatisfaction, complaint and pressure can usually be considered as major factors for having more accessible and safe roads during winter. These pressures have contributed and led to an increasing critical approach focusing on public procurement of these services after some harsh winters in the recent years in Sweden with traffic disruption and delay as consequence i.e. an increasing focus on the way in which the Swedish state authorities and local governments procure winter road maintenance services. The present study which is part of a larger research project investigating efficient winter road maintenance through procurement, tendering and contract aimed at extending this knowledge base with regard to procurement and socioeconomic factors with focus on the winter maintenance of the Swedish road network. The study reveals that even the Swedish winter road maintenance services are procured and outsourced in accordance with EU directive and public procurement rules transposed into the Swedish act on public procurement, the act has been interpreted in a manner that all the process has led to great dissatisfaction of end-users during winter due to improper bundling of winter related services. The lack of economic motivation in current contracts concerning winter road maintenance in the form of incentives has led to an inefficient performance of winter road measures. The study suggests a number of proposals in order to make forthcoming contracts more effective through proper bundling of winter services and create incentives for contractors to improve the performance of winter road maintenance services.
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| 8. |
- Abdi, Adel, et al.
(författare)
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Use of Road Weather Information System (RWIS) as Assistive Tool for Effective Winter Road Maintenance : Technical andContractual Interactions
- 2012
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Ingår i: International Journal of Engineering and Technolgy. - 2049-3444. ; 2:12, s. 2002-2012
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Tidskriftsartikel (refereegranskat)abstract
- Winter highway operation and maintenance in the northern periphery is a challenge, a broad and complex area. Understanding about this area and its effect on winter traffic performance is far from complete. During the last forty years since Swedish Transport Administration (former Swedish National Road Administration) began attempting of the use of Road Weather Information System -RWIS on the Swedish road network, the repair and maintenance methods of this assistive tool has dramatically changed. Changing of the methods have been due to the progress and development of the technology within this area i.e. from simple stations that could be connected via telephone network for icy road warning to amore sophisticated and modern internet based technology. The main objective of this study was to investigate and find the importance and effectiveness of using weather data collected from RWIS by road agencies as an assistive tool for effective performance of winter road maintenance, and how these tools are currently maintained without influencing the delay of winter road maintenance.The study also attempts to find possible interactions between technical and contractual issues that may affect winter road maintenance. The method of the study was partly based on a theoretical study by reviewing some internationally published articles and reports in this area and furthermore a domestic questionnaire survey, an internationalbenchmarking and a follow-up study within a selected region in Sweden. The results of the study reveal that even if the weather stations are normally placed on roads where the risk of icy roads is greatest, there are indirect factors which influence the planned maintenance of these tools which subsequenly cause delay of winter road maintenance.
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| 9. |
- Bekele, Abiy, et al.
(författare)
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Application of Energy-Based Crack Initiation Approach to Low-Temperature Damage and Recovery Based on Noncontact Resonance Testing
- 2020
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Ingår i: Journal of materials in civil engineering. - : American Society of Civil Engineers (ASCE). - 0899-1561 .- 1943-5533. ; 32:9
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Tidskriftsartikel (refereegranskat)abstract
- Low temperature has a tendency to cause microdamage in asphalt concrete because of the relative thermal contraction of mastic and subsequent accumulation of thermal stresses. This paper presents the applicability of an energy-based micromechanical approach for assessing low-temperature damage and recovery in asphalt concrete based on a newly developed noncontact resonance testing. The principle of local energy balance and redistribution was applied to estimate average thermal microcrack length by considering local thermal strain energy release zones and surface energy of cracks initiated at preexisting air voids. A damage probing test was carried out by thermal loading and unloading of five different asphalt concrete specimens. The test was carried out by using a recently developed noncontact resonance method. The stiffness modulus was determined from the resonance test and utilized in the energy balance and redistribution formulation. Coefficients of thermal contraction of the specimens were also determined based on the noncontact resonance test and by applying the principle of the impact-echo method and calculating changes in thickness of the test specimens.
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| 10. |
- Bekele, Abiy, et al.
(författare)
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Automated Non‑contact Resonance Excitation Method to Assess Low Temperature Dynamic Modulus of Asphalt Concrete
- 2019
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Ingår i: Journal of nondestructive evaluation. - : Springer Nature. - 0195-9298 .- 1573-4862. ; 38:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the applicability of an automated non-destructive testing method to monitor the stiffness of asphalt concrete at low temperatures. A loudspeaker is used as a source of non-contact excitation of the axially symmetric fundamental resonant frequencies of a disc-shaped asphalt concrete specimen positioned inside an environmental chamber. Measured resonant frequencies are used to calculate the dynamic moduli of the specimen at different temperatures. The repeatability of the method as well as the effect of loudspeaker height above the sample are studied. Results show that the main advantage of the non-contact excitation method, compared to manually applied impact hammer excitation, is that repeatable automated measurements can be performed while the specimen is placed inside an environmental temperature chamber. This methodology enables to study the effect of only low temperature conditioning on the dynamic modulus of asphalt concrete without interference from mechanical loading.
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