“…This class of problems aim to find the optimal replacement schedules (or more generally, the purchase and retirement schedules if the number of assets is not fixed) of assets (in our case, the vehicles) that minimize the total cost over a given planning horizon. The assets considered in these problems are interdependent due to budget constraints (Karabakal et al, 1994;Lee and Madanat, 2015;Lee et al, 2016;Zhang et al, 2017), economies of scale (Jones et al, 1991;Büyüktahtakın et al, 2014), demand constraints (Wu et al, 2003;Wu et al, 2005;Guerrero et al, 2013;Guerrero, 2014;Seif et al, 2019;Shields et al, 2019), or combinations of the above (Büyüktahtakın and Hartman, 2016;Des-Bordes and Büyüktahtakın, 2017).…”