Accident Investigation Body (AIB)
An Accident Investigation Body (AIB) is the independent national authority required in each EU Member State under Directive (EU) 2016/798 to investigate railway accidents and serious incidents for the sole purpose of improving safety — not to apportion blame or establish legal liability.
Legal basis and independence
Article 22 of the Railway Safety Directive mandates that each Member State maintain a permanent investigating body structurally independent from infrastructure managers, railway undertakings, ERA, national safety authorities, and any party with a potential conflict of interest. Investigators must hold status guarantees of independence. The investigation runs parallel to and separately from any judicial inquiry into the same occurrence; investigators are granted access to evidence and witnesses independently of the judicial process.
Scope and process
The AIB must investigate all serious accidents — defined as collisions or derailments resulting in at least one fatality or serious injuries to five or more people, or causing extensive damage to rolling stock or infrastructure. For other accidents and incidents, the AIB decides at its discretion whether an investigation serves a safety benefit. The body must decide within two months of notification whether to open a formal investigation.
Investigation reports are published and must follow a harmonised structure under Commission Implementing Regulation (EU) 2020/572. Reports include safety recommendations addressed to infrastructure managers, railway undertakings, manufacturers, and national authorities. Those recommendations do not carry legal force, but addressees are required to act on them and report back.
NIB Network
AIBs across the EU, plus Norway and Switzerland, coordinate through the NIB Network, supported by ERA’s secretariat. The network develops common investigation methods, conducts peer reviews of individual bodies’ effectiveness, and publishes annual summary reports. It operates under Article 22(7) of Directive (EU) 2016/798.