The presence of gas and liquid flowing simultaneously in pipelines made of several uphill and downhill sections can lead to the formation of long liquid slugs which are blown from one pipeline section to the next due to gas pressure. This terrain-induced slugging gives rise to undesirable unsteady flow conditions. In this paper, a transient two-fluid model is validated for conditions of terrain-induced slugging. This model contains new correlations, for the drag coefficient and the virtual mass force for the slug flow regime, that were presented in previous papers. An experimental study of terrain-induced slugging in a laboratory scale pipeline, made of two uphill and two downhill sections, is also reported. This provides data for the model validation. The model predicts all the major features of the data, and is in good quantitative agreement as well.