Reliability, Availability and Maintainability Analysis of Addis Ababa Light Rail Transit Signaling System
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Date
2017-07
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Addis Ababa University
Abstract
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%.
Description
Keywords
AA-LRT, Signalling system, Axle Counter, Reliability, Availability, Maintainability, RAM, Failure Mode and Effect Analysis (FMEA), Risk Priority Number (RPN)