Solid waste collection problems are of increasing concern to expanding cities and sectors with high volumes of waste generation. This paper deals with the optimization of a collection system in the sidewalk for urban sectors. This is a combinatorial problem in which all arcs of a mixed network are traversed, subject to vehicle capacity and time restrictions. A flexible formulation is proposed which works with separate collection and transportation networks. A sequencing scheme to assign routes is also proposed. The performance of the model is analyzed under different scenarios and applied to a collection zone of Bogotá with satisfactory results.