In preparation of new legislation, in which zoning distances for underground transmission pipelines in the Netherlands will be based on a probabilistic approach, the quantitative risk analysis methodology for these pipelines is revised to reflect new understandings in the risk scenarios, failure frequencies and effects. Additional measures should be applied to reduce the risk if, for example, dwellings are situated within the new zoning distances, or if the guidance value for the societal risk is exceeded. In this framework, three types of pipelines are distinguished based on the transported substance: natural gas, flammable liquids, and all other dangerous substances. For all three types of pipelines, risk methodologies have been developed. In order to assess the possible (maximum) effectiveness of measures on the overall failure frequency, and to prioritize in adopting these measures, it is first necessary to determine the contribution of the various failure causes to the probability of failure of a pipeline. For deriving the failure causes, different sources were analyzed depending on the type of pipeline: for natural gas pipelines data from the Dutch gas industry were used, for pipelines with flammable liquids data from CONCAWE were used, and for other pipelines the failure causes were derived from the accident databases MHIDAS and FACTS.