Add definitions to Cause and Effect values

[skalexch]

Summary

This proposal adds definitions to cause and effect values.

Describe the Problem

Cause values and most Effect values have no definitions. And the few Effect values that are defined need clearer definitions (e.g. Accessibility Issue).

Use Cases

Proposed Solution

MobilityData drafted definitions for Cause and Effect values which were further discussed in the RT Working Group meetings of March and April, 2026.

Type of change

GTFS Schedule

• Functional Change
• Non-Functional Change
• Documentation Maintenance

GTFS Realtime

• Specification Change
• Specification Change (Experimental Field)

Additional Information

Proposed Discussion Period

Testing Details

• Consumer(s):
• Producer(s):
• Estimated Testing Period:

Proposal Update Tracker

Date	Update Description
(YYYY-MM-DD)	(Brief description of the update)

Checklist

• I have read and understood the GTFS Change process.
• I have read and understood the GTFS Guiding Principles.
• I understand the Role of Advocate and the Responsibilities attached to it.
• I have signed the Contributor License Agreement (CLA).
• I have ensured that this proposal is not covered by an existing Pull Request.