\r\nInfrastructure manager Prorail says the punctuality on regional lines, most of which are single track and have frequent services, is higher than on the core network, at 95.2%. When the delay criteria is increased from three to five minutes, the overall punctuality rises to 96% despite the frequency of trains on the network increasing considerably in recent years.\r\n \r\nProrail says the higher frequency of trains amplifies the effects of a delay and what might have previously been a minor event can quickly snowball into a major disruption. More than 60% of interferences are caused by external circumstances, including extreme weather, which Prorail says it has a tough policy to manage.\r\nThe HSL South high-speed line continues to experience problems with performance with punctuality over the past 12 month at 85%, dropping to 81.9% in May, with numerous services on HSL - South delayed or cancelled. Netherlands Railways (NS), which operates the services on the \u201ccore network\u201d including HSL - South, says the rerouting of The Hague Central - Eindhoven twice per hour via HSL- South is causing major delays. Both NS and Prorail agree that HSL - South needs modifications and improvements, and NS does not expect performance on the line to improve this year.