Browsing by Author "Jigsa, Tesfaye (Mr.)"

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    eveloping and Analyzing Automated Tests for Computer Based Interlocking System The Case of AA LRT
    (Addis Ababa University, 2016-06) Bira, Kawo; Jigsa, Tesfaye (Mr.)
    Railway system has safety, economic and environmentally critical system because its failure may cause serious consequences of loss human life, serious injuries, and large scale of environmental damages or considerable economical penalties. Therefore we have to guarantee that they are designed and put into operation properly. Thus, no error can be tolerated in the operation of the system. Interlocking system is used for ensuring the safety of trains. Interlocking systems control all wayside elements in railway traffic. These systems are accountable for safe train operations and must prevent collisions and derailments of the train. Testing the interlocking systems is a key focus. Before start the train operation must be test all equipment according to the interlocking law and safety regulation. In general there are two type of testing approach in railway system that is manual and automatic. Both have on their own advantage and disadvantage. Automation has two major benefits; it saves the verification time and reduces the risk of manual errors. In order to verify whether an interlocking system is consistent with the system requirement specification, it is necessary to carry out a series of testing. In this thesis to verify the interlocking system use control tables, Boolean function, flowchart, a computer aided tool for the generation of test cases is studied and implemented. A number of test purpose models have been created to direct test case against the interlocking. These test purpose models were implemented in C sharp and Sql server. The entire test setup can be run on any PC and does not require the interlocking hardware. This method can be applies to a number of smaller interlocking systems and partly to the more complex of AALRT depot and station. Simulations have GUI to interacts the user with the system and enable easy visualization of the movement of the train. The user can inject different possibility of testing mechanism. One testing mechanism was unavailable list of Tracks or Switch interlocking elements. Other methods are using randomly occupied of Tracks and changing of the switch position. Result show that with 7 routing selected 21 conflicting and 64 derailment of the train are verified and validated. The verification is comparing the expected result with the actual simulations. This simulations tools are used for addition verification that support for AALRT.
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    Improving Safety of Rail Operation by Risk Management of Accidents at Level– Crossing: case study of AA-LRT
    (Addis Ababa University, 2017-06) Getaneh, Amene; Jigsa, Tesfaye (Mr.); Birhanu, Reesom (Mr.) Co-Advisor
    Ethiopian Railway Corporation has constructed a light rail transit for Addis Ababa. The LRT Project in Addis Ababa, the capital city of Ethiopia, consists of the East-west Line and the Southnorth Line. Risk management involves assessing the risk sources and designing strategies and procedures to mitigate those risks to an acceptable level. This paper considers the assessment of engineering infrastructures, human factors and surrounding environment as the three main factors contributing or determining accident at railway level crossings (RLC). Accidents at railways level crossings clearly dominate the railway accident. An important first step towards eliminating the cause of these accidents is through understanding and assessing the risks associated with a given level crossing and acting on them. This paper introduces a risk management process which involves several activities, including, hazard identification, risk evaluation, risk assessment, risk treatment and control and illustrates how it can be systematically applied to mitigate risk to AA-LRT level crossing. Improving safety of rail operation by risk management of accidents at level–crossing is considered as significant as a guarantee of the safe, efficient operation of the whole railway and to better safety at level crossings and upgrades to improve level crossings safety performance. Railway level crossings, which are used by high number of vehicles and trains each and every day, can severly affect the efficiency and safety of road. Railway safety will be improved by organized risk management system for assessing level crossing safety and safety enhancement measures. Human factors and technical factors are the two major factors of accidents at AA-LRTS. Guard fence damaged and signal equipment damaged is considered as intolerable risk in AA-LRTS and none of the accidents recorded are broadly acceptable. Railway-controlled crossing has low cost, minimum delay and high safety and best for the future AA-LRTS. Generally; this thesis presents improvment in safety of rail operation of Ababa-Ababa LRT by risk management of accidents at level–crossing.
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    Reliability, Availability and Maintainability Analysis of Addis Ababa Light Rail Transit Signaling System
    (Addis Ababa University, 2017-07) Alemu, Ayana; Jigsa, Tesfaye (Mr.); Abebe, Teklu (Mr.)
    The railway network is a complex and distributed system with several technologies working together to fulfil the demands on capacity, speed and mobility to transport goods and passengers. The railway transportation system in Addis Ababa, the capital of Ethiopia plays a vital role in sustaining social and economic activities of a country by providing a safe, reliable, environmentally friendly and cost efficient means of transportation for the people. Following the safe, economical and practical principles, the design of Addis Ababa Light Rail Transit (AA-LRT) chooses a reasonable communication and signal system. Quality of transportation system critically depend on the reliability of signaling systems. Despite their numerous advantages, considerable train delays, cancellation, high maintenance cost and passenger dissatisfaction are the main disadvantages of signaling systems failures. Reliability, Availability, and Maintainability (RAM) analysis is a practical technique that uses failure and repair dataset obtained over a reasonable time for dealing with proper signaling system operation, maintenance scheduling, cost control, and improving the availability and performance of signaling systems. This research study and analyse RAM of AA-LRT signaling system with a historical database of failures and repairs of signaling systems was collected in the whole line of AA-LRT over a period of six months operation. After data analysis, it was revealed that the Axle counter subsystem has the highest failure frequency with relatively low availability and the switch has the lowest failure frequency with highest availability. A failure Mode and Effect analysis (FMEA) result shows that the switch is most critical subsystem to cause risk. Similarly, estimating the availability of failed signaling subsystems and equipments indicated that all subsystems have an acceptable availability level of above 96%.