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Hydrocarbon pipelines transporting compressible products like methane or high-vapor-pressure(HVP)liquids under supercritical conditions can be susceptible to long-propagating failures.As the unplanned release of such hydrocarbons can lead to significant pollution and/or the horrific potential of explosion and/or a very large fire,design criteria to preclude such failures were essential to environmental and public safety.Thus,technology was developed to establish the minimum arrest requirements to avoid such failures shortly after this design concern was evident.Soon after this technology emerged in the early 1970sit became evident that its predictions were increasinglynon-conservative as the toughness of line-pipe steel increased.A second potentially critical factor for what was a one-dimensional technology was that changes in steel processing led to directional dependence in both the flow and fracture properties.While recognized,this dependence was tacitly ignored in quantifying arrest,as were early observations that indicated propagating shear failure was controlled by plastic collapse rather than by fracture processes.