Analysis of Track Geometry Quality Index for Addis Ababa Light Rail Transit
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Date
2022-04
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Addis Ababa University
Abstract
The use and need of railway transportation system is increasing due to different reasons;
it uses less energy, environmental friendly, high speed and huge capacity. The increment
of axle loads leads to the design of high quality track structure materials in order to
enhance the life span of the line. Even though, the track structure is designed for a longer
design period, its performance is reduced from time to time. For this reason the status of
the structure should be assessed periodically. The aim of this research is to analyze the
track geometry quality index of Addis Ababa Light Rail Transit (AALRT).In order to
conduct this research deterministic statistical method was used. The track quality index
model was developed using multiple linear regression analysis. In this method the average
track irregularities of cross level, alignment, twist and gauge parameters were used as an
independent variable whereas the track quality index was used as a dependent variable or
response. The result showed that most of the common track irregularities in AALRT were
cross level and gauge irregularities which cover 60 % and 32 % of the total irregularity
percentage respectively. The research found that the maximum value of track quality index
is 9.51 mm which was 63.4 % of the threshold limit (15mm). The rate of change of track
quality indices were calculated for twelve segments. The maximum rate of change of track
quality indices (track deterioration rates) was 7.54 mm/yr which was found in curves with
embankment (ballasted track). Finally, the adequacy of the developed track quality index
model was checked based on the assumptions of multiple linear regression and also it is
validated using variance inflation factor (VIF).The VIF values of the four independent
variables; i.e., cross level, alignment, twist and gauge irregularities are 1.12, 1.11, 1.03
and 1.08 respectively were less than 5. As a result, the model is valid and can be used in
the future to show the status of the track and manage track maintenance activities.
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Keywords
Track Quality Index, Maintenance, Statistical Model, Deterministic Method