non_ascii_or_non_printable_char: GTFS validation rule (data quality) Warning
A field contains non-printable control characters (tab, vertical tab, form feed, etc.) or non-ASCII characters that may not survive ASCII-only consumers.
What the rule checks
A field contains non-printable control characters (tab, vertical tab, form feed, etc.) or non-ASCII characters that may not survive ASCII-only consumers.
Severity: warning
A warning marks data the specification allows but that looks doubtful, or recommended information that is missing. The GTFS can still be published, but riders may see the effect, so each case deserves a look.
Where it applies
The rule measures the quality of the data rather than strict conformity: it points at values that are allowed but unlikely.
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 non_ascii_or_non_printable_char 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, non_ascii_or_non_printable_char. Its documentation describes each rule: MobilityData validator rules.