Track Surveying and Speed Optimization (Case Study of Addis Ababa – Adama Line)
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Date
2016-02
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Addis Ababa University
Abstract
Speed Optimization is a means of improving the geometric alignment, infrastructure and
construction materials and structure performance during the working cycles under some manufacturing,
operational and failure conditions as well as cost limitations.
The new Ethiopian national railway network design speed is about 120Km/h which is too low when
compared with some developed countries rail speed. Construction of new high speed line needs huge
investment that may not be viable for a developing country like Ethiopia and optimization of existing line
using different techniques is the available option. The major anticipated problems/demand behind for
high speed for the country national rail network and Addis Ababa – Adama line in particular are for that
it is Competitive with toll road of same speed, located along the development axis area of Ethiopian
economy, located along country’s industrial zone highly polluted by industry emission, national image
building, attracting investor and delay of freight at sea port.
Optimization of speed were done by enquiring and analyzing existing track geometry and track super
structures, construction materials and other speed related parameters to identify restrictive sections and
the maximum allowable speed of the line. Geometric analysis and design were done by Bentley Inrail
software in the optimization process and finite element methods were used for analyzing of track
component response under optimized speed.
From the analysis result, the existing track construction materials and infrastructures are within
recommendable limit for introducing high speed. The geometry of the track is allowable for speed up to
130km/h by modifying cant of sharp horizontal curves. Two optimization techniques were identified for
the study. The first optimization technique is introducing tilting coach and the second is upgrading
existing geometric alignment. On the existing track, 160km/h speed can be operated by introducing tilting
coach without upgrading the track alignment. It is possible to achieve 16okm/h for conventional train by
upgrading sharp horizontal curves less than 1325m. By combination of both techniques 205km/h speed
can be achieved, but due to vertical curve limitation speed more than 170km/h is not viable on the line.
By all optimization techniques, the recommendable level of optimization percentage is 33%. Introducing
tilt coach technology is recommendable technology as it is easy for application and economically feasible
option. Since the entire Ethiopian national rail network are similar, the work done for Addis Ababa –
Adama line can be projected for other routes to increase consistency system throughout the country.
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Keywords
Speed optimization, conventional train, tilting coach, allowable design speed, high speed, track geometry, Bentley Inrail Software