Thin bituminous surfacing as an alternative surfacing type for low volume gravel roads in Ethiopian roads authority;life cycle cost comparison and economic analysis

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.