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duplicated_column: GTFS validation rule (archive structure) Error

Two columns in the same CSV file share the same name.

Updated on 23 October 2026

What the rule checks

Two columns in the same CSV file share the same name.

Severity: error

An error marks data that breaks the GTFS specification. A journey planner or a rider app may refuse the file, or show a wrong version of it. Correct it before publishing the GTFS.

Where it applies

The rule applies to the structure of the GTFS archive: the files it holds, their headers, their encoding and the shape of their rows.

Finding and correcting it

Open the GTFS in GTFS Express. Reading is free, and the validation, by the MobilityData validator and the rules of GTFS Express itself, lists the occurrences of duplicated_column with the file and rows involved. The correction is made in a draft, by hand or from a brief, with the licence: the corrected GTFS is validated again before it is delivered, and the change can be undone.

In the MobilityData validator

The MobilityData GTFS validator uses the same code, duplicated_column. Its documentation describes each rule: MobilityData validator rules.

Rules of the same domain