A number of preventive measures are taken to keep underground pipelines in good condition. Aboveground pipelines are coated and have to undergo regular sight inspections. Underground pipelines are coated and cathodically protected against corrosion. The integrity of the transport system is monitored with the help of a continual inspection programme. Internal inspections are performed with intelligent pigs that are driven through the pipeline by the gas flow. The data is collected and analysed and, where necessary, adjustments are made to the network. Hundreds of kilometres of pipeline are inspected internally every year. In addition to this, pipelines that cannot be inspected by using robots are monitored by aboveground inspection methods falling within the External Corrosion Direct Assessment (ECDA) integrity approach.