Failure Analysis and Improvement of Level Crossing Signaling System of Addis Ababa-Light Rail Transit
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Date
2017-08
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Addis Ababa University
Abstract
Railway level crossings signalling systems are the most cause of concern for both rail and road
authorities. Level crossings are one of the most crucial parts of the railway lines as two different types
of transportation intersect at these points. The principle objective of this thesis represents the failure
analysis of level cross in Addis Ababa Light Rail Transit signalling system: employing model-based
failure analysis methods and system fault tree, causes and effects, major failures investigated. The
improvement of the level cross signalling system after doing complete failure model and optimisation,
determination of quantitative aspects such as probability of occurrence of hazard, forecasting about the
system which is important in expansion and development of system.
First from the current AA-LRT railway level crossing signaling system installation and
configuration, feared event model is developed (Collision between train and vehicle) by a Fault Tree.
Second, perform in-depth analyses of the reliability, availability and maintenance of AA-LRT railway
level crossing signaling system with initial design failure and repair rate data used to estimate the
reliability, availability and maintenance for each subsystem. The system is classified in different
subsystems in series like barrier, axle counter, rail signal, LC controller and interlocking
(CBI).Mathematical model of these subsystems have been developed using Markov modeling. Third,
study methodologies selected which are quantitative, analytical data analysis methods are evaluated and
graph is plotted for different time intervals. The analysis from this thesis shows that the reliability of
barrier, axle counter, rail signal, LC controller and CBI are 0.44, 0.94, 0.98, 0.90 and 0.90
consecutively after 10000, the reliability of the whole level crossing after 10000 hour and
maintainability of Barrier, Axle counter, LC controller, rail signal and CBI after one hour are 0.865,
.899, 0.926, 0.939, and 0.909 respectively according to the design data.
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Keywords
Level crossing, failure propagation, failure modes, modeling based failure analysis, reliability, availability, maintainability (RAM), Markov modeling