Optimization model for transit fleet replacement with budgetary and environmental constraints

Abstract

Equipment is replaced when the value of new equipment is more attractive, because maintenance and operation costs increase with time usage. Some methods have been developed to solve this problem. In the public transport sector, these problems are frequently analyzed by fleet managers, due to the bus age restrictions laws. In this case, beyond replacement, other lower cost alternatives were also proposed and analyzed, such as rehabilitation and remanufacturing of vehicles. We propose an Integer Programming model that integrates both of the constraints referred above, namely budgetary and environmental constraints (CO2 emissions), which have been treated in isolation themselves in the literature, as far as we known. The study aims to determine the optimal plan for the replacement of diesel vehicles of a fleet with different sizes, ages, maintenance costs and emissions rates, with new (less pollutant) diesel vehicles over a time horizon of 50 years. This study was developed in a transit agency in the Joinville city, Brazil. The results indicate that it is possible to reduce emissions with a low annual budget using an optimal replacement policy.