Segment-based maps are emerging as an efficient way to represent the environments in which mobile robots operate. When compared to grid-based maps, maps composed of line segments usually need less space to be stored. However, very little effort has been devoted to methods that allow to reduce the size of segment-based maps by removing redundant line segments that represent the same object in the environment. This problem is usually addressed with rather ad hoc methods that are embedded in mapping systems. In this paper, we put forward the problem of reducing the size of segment-based maps by presenting a survey of the existing methods and by experimentally evaluating some of them. Our results can be used to set out some guidelines for the development of a general approach to reducing redundant line segments in maps.