Life cycle cost analysis to identify the need for drainage renewal in maintenance of road asset: Case Studies from a New Zealand road network

This paper presents life cycle cost analysis case studies of drainage improvements in pavement renewal sections. The methodology used was developed by the New Zealand Transport Agency (NZTA) and utilizes Net Present Value (NPV) and Economic Indicator (EI) as the tools for economic justification. Case studies on a number of renewal sites were conducted from a road network managed under a Performance Specified Maintenance Contract (PSMC) in New Zealand (NZ). Due to the contractual nature of a PSMC, that is a lump sum to manage the network for 10 years, the contractors are at risk of expensive maintenance and renewal costs from premature failure. Consequently, they have to be proactive in balancing investment for asset renewal, preventive and reactive maintenance on the road network. The majority of the network comprises of chipseal roads without any comprehensive drainage measures being present. The renewal sites selected for the case study range from flat rolling ground to rugged hilly terrain. There are side hills, natural streams, and bush areas beside the sites, thus making them particularly vulnerable to moisture induced failure. The outcome of the study is encouraging and indicates a positive gain in economic efficiency from the investment in drainage improvement. This study is the first step towards managing drainage on a road network in a more holistic manner, by identifying the costs and benefits of undertaking the appropriate investment.