Many countries have tried to solve transportation problems through Intelligent Transportation System (ITS), which has been spread since early 1990's in the world. Some ITS devices have been operated for the period longer than expected, and the others not. This study proposed a way to determine an economic lifetime of ITS devices based on failure records. In order to describe the procedure proposed in this study, a fundamental idea to determine a lifetime of devices was introduced derived from engineering economics. Cost items were described to obtain maintenance costs for ITS devices,and the estimation of a maintenance cost curve from wear-out failure records which is not enough was explained. In order to evaluate this methodology, a case study was conducted to estimate a lifetime of 76 variable message signs (VMS), which have been operated on an urban area in Korea for 7 years. To estimate a maintenance cost curve on wear-out failures, an exponential model was selected on the basis of R2 and p-value. At the last step,the lifetime of a VMS was determined to 8 years at which an annualized equivalent cost was minimized. This study is expected to contribute to efficient management of ITS devices through applying an appropriate lifetime.
Samenvatting