CEN working groups provide a consensual process to evolve standards and have formal procedures and timeframes managed through the standards bodies of the European nations. New feature proposals can be submitted to the NeTEx working group by sending an email at info<at>netex-cen.eu and will be considered along with other suggestions for a future enhancement to the standard. Under the CEN process a  New Work Item request is created to manage the enhancements to a specification, with a versioning process to identify sets of changes.

Adding new features specific to country, supplier or any smaller area can be done using NeTEx extension mechanisms (Key Value extensions/ Extension Tag). These can also be used to develop new candidate features ahead of formal incorporation. See also ‘Can I add my own codes to NeTEx’?