Abstract:
Road infrastructure is one of the most important assets for the Economical, Political and
Social development of one country. And there are unsurfaced or lightly surfaced low volume
roads. Huge investments are made annually to maintain and improve their functions. Double
otta Seal is one type of thin bituminous surfacing and usually has a design life span of 15 to
16 years whereas gravel road has design life span of 8 to 10 years. Considering their life
span it is necessary to determine which surfacing is more economical for entire life. The
objective of this research was to identify which type of surfacing is economical for low volume
roads in Ethiopia on selected sections of Ethiopian Roads Authority namely, Woito - Turmi,
Agbe - Sekota and Metu – Alge by using the existing road condition. Life cycle cost
comparison and economic analysis carried out for three selected sections of ERA, cost break
down analysis for initial costs of double otta seal surfacing, traffic analysis, and user costs
were performed for carrying out economic evaluation of the three sections and the present
worth method was used for the evaluation of life cycle costs of both surfacing. The life cycle
cost comparison and economic analysis was conducted by using HDM-4 model software.
From the result, the double otta seal had the total cost of 15,362,00.00 birr, 25,520,000.00
and 30,678,000.00 birr per km during their design period for Woito – Turmi, Metu – Alge
and Agbe – Sekota road section respectively. Whereas gravel roads had the total cost of
19,522,000.00 birr, 31,435,000.00 birr and 37,810,000.00 birr per km during their design
period for Woito – Turmi, Metu – Alge and Agbe – Sekota road section respectively. The
roughnesses of the selected roads were improved and the road user costs of double otta seal
were smaller than gravel roads.
It was found that Double otta seal surfacing was found more economical and feasible than
gravel roads. Implementing Authorities should be give consideration to the use of the Otta
seal as an alternative rather than continuous gravelling/re-gravelling.
