We consider a metro network design problem in which the objective is to maximize the origin/destination traffic captured by the system. The lines of the network are located within some corridors that are also determined by the procedure. The amount of captured traffic depends on the ratio between travel time by metro and travel time using alternative modes. There is a limited construction budget. Lower bounds are imposed on the angles between alignments, which allows the generation of different network shapes. A matheuristic is proposed to solve the problem. The method is applied to a test case from the city of Concepción, Chile.