NoBo / DeBo / AsBo — the three assessment bodies

EU rail conformity assessment runs through three kinds of independent body, and mixing them up is one of the sector's classic confusions. A Notified Body (NoBo) assesses conformity with TSIs: it runs the EC verification of a subsystem or interoperability constituent and issues the certificates the authorisation file is built on. A Designated Body (DeBo) does the equivalent job for notified national rules — the requirements that still exist where TSIs leave open points or specific cases, or for legacy compatibility. An Assessment Body (AsBo) is different in kind: under the Common Safety Method for risk evaluation (CSM-RA), it independently assesses whether a proposer's risk-management process was properly applied for a significant change — it audits the risk assessment itself, not conformity with a document. One project routinely involves all three: the NoBo certifies TSI conformity of the new signalling, the DeBo covers the national-rule remainder, and the AsBo signs the safety-assessment report the safety authority relies on. All three must be accredited or recognised, and their reports feed ERA's one-stop shop for authorisations.