Urban bus fleet-to-route assignment for pollutant emissions minimization

•A methodology to fleet-to-route assignment for emission reduction is proposed.•Routes are distinguished by considering their operational characteristics.•Mathematical emission models in the optimization problem are used.•A Mixed Integer Linear Programming optimization problem is formulated.•Application to real data of Madrid City to distribute urban buses fleet.

This study proposes a methodology to optimize the assignment of an urban bus fleet to a set of fixed routes, taking into account the differences among routes and the differences among vehicle types and propulsion technologies in order to reduce pollutant emissions (CO2, CO, THC, NOx and PM). A Mixed Integer Linear Programming optimization model is stated and two scenarios are assessed: minimization of CO2 and NOx. The results show that it is feasible to obtain a fleet distribution in which emissions for any given pollutant are reduced without increase in emissions of other pollutants.