The safety of road embankments is mainly assessed in the engineering practice by limit equilibrium analyses. Locating the critical slip surface of embankments and calculating the corresponding factor of safety is a crucial task. In this paper, the continuous ant colony optimisation algorithm is used to analyse the stability of slopes with non-circular slip surfaces. To illustrate the proposed procedure, one example from published literature and another engineering case study of a landslide at a road construction site in India is analysed. This latter study is supplemented by the results of geotechnical investigations performed before and after the failure of the embankment. The results demonstrate that the proposed technique identifies correctly the critical slip surface and can thus be used for engineering applications.