Life Cycle Cost Analysis of Flexible Pavement with Geosynthetic Materials and Conventional Flexible Pavement

Abstract

By the time the need for minimizing the costs of a road infrastructure became a necessity, LCCA had grown to be an accepted practice in the world. It was not a piece of cake for the National Cooperative Highway Research and Intermodal Surface Transportation Efficiency Act to perform a comprehensive and reliable LCCA at the time when the available information was not sufficient. Researches conducted in this area consistently confirmed that developed countries have a published Policy statement on LCCA, instructional LCCA workshop and resultant noteworthy technical bulletin outlining the best practice of LCCA methodology and related parameters. The revers is true in Ethiopia eventhough the country is about to be emerged out of road infrastructure problem, except from the challenges posed by new commitments to the economical consideration. This is because decisions have been based on a comparison of initial construction costs concept setting lowest initial construction cost option as the lowest total cost option. As such, it was aimed to determine the overall cost of flexible pavement with and without geosynthetic material and evaluating its cost effectiveness. The true cost (LCCA) was adopted as it has the means to fulfill these requirements. This was achieved by determining the agency, user and environmental costs for the road segment under study. In this regard information like traffic data and pavement data was collected from concerned agencies. Design documents were taken from ACRA. Travel speed on the road segment, discount rate, design period, analysis period and base year were selected based on the experience of ACRA. An Indian department of transportation vehicle class were adopted and Percentages of Truck distribution were determined by conducting a sample of field survey. Accordingly, observation of sample field survey revealed that out of 100 vehicles on the road segment under study 65% were passenger cars, 20% were single unit trucks and 15% were combination trucks. Estimation of costs was done specific to each construction, maintenance and rehabilitation treatment. Two alternative methodologies were provided: one was using a per-lane length approach which incorporates updated market prices and contract data from design document and this was adopted in determining agency cost associated with maintenance and rehabilitation. The other approach was one that builds the costs from a developed model. This approach was adopted to determine the initial construction cost of both alternatives. Accordingly, Agency cost was determined to be 3,182,653,893 and 1,580,443,895 ETB for Conventional and Geosynthesized pavement respectively. This conveys a message that using geosynthetic material in flexible pavement can reduce an Agency cost by 50.34 %. But using initial construction cost as a decision-making tool can eliminate this fact and leads to wrong direction. This is because of the fact that avoiding this fabric can reduce initial construction cost by 1.5%. On behave of user costs, only work zone user costs were given prominent coverage in this paper and costs associated with noise, and pollution should not be a formidable concern as they are not expected to vary significantly by LCCA alternative. The seven user cost components associated to work zone operation (Travel Delay Costs & Vehicle Operating Costs) were determined. Accordingly, Inspection of analysis part in this paper reveals that, user cost was determined to be 14,178,855,923 & 4,120,182,985 ETB respectively putting the former one conventional FP. This implies that about 70.9% of user cost can be avoided when using a geosynthetic materials. Finally, Economic evaluation of the two alternatives was carried out using the NPV as economic indicator. As such incorporating geosynthetic material in pavement was found more economical and most effective alternative pavement option