Assessment of The Reliability of The Traffic Forecast and Its Impact on Pavement Design and Service Life” (A Case Study Three Ethiopian Road)
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Date
2020-08
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Addis Ababa University
Abstract
Unrealistic or incomplete estimates of traffic characteristics during design process will affect
determination of pavement type, performance of the pavement structures for the design life
as well as construction and maintenance cost. Thus, accurate estimation of traffic loading is
needed for a better design of pavement structures, easy of construction and maintenance as
well as cost effective.
Three road projects here selected for this study, the one Shashemene-Dodola pavement design
which is overestimated future traffic and result high capital cost of construction (increase use
of construction materials, resources). The other two projects Alemgena-Butajira and
Debrebrihan-Karakore pavement design are underestimated future traffic and it pre-matured
pavement failure which results a high capital cost of maintenance and increases vehicle
operation cost.
This study assesses the existing practice of traffic forecasting for pavement design and
recommend potential improvements of procedures. This process and its results have been
coordinated in order to be incorporated in traffic volume estimation. Two traffic growth rate
estimation method is adopted i.e, Regression and Elasticity Analysis from traffic counts and
for determination of forecasted traffic volume.
The study result indicates, the change between actual traffic volume which is counted during
the road service time by Ethiopian Roads Authority and traffic volume estimation of using the
above methods is within 0% to 4% whereas, the change between actual traffic and design
traffic is -87% to 51%.
From the result of calculated cumulative standard axel load and determining traffic class of
the pavement, analyzing the difference in traffic class of the design traffic and study traffic is
carried out. Finally determining the impact of inaccurate traffic volume and loading estimation
on pavement performance and analyses additional cost of construction and maintenance due
to inaccurate traffic volume estimation.
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Keywords
Traffic Forecast, Pavement Design, Service Life, Ethiopian Road