[skalexch]

Summary

This proposal corrects the requirements for min_transfer_time, making the field forbidden when transfers are not possible (transfer_type=3) or are in-seat transfers (transfer_type=4).

Describe the Problem

min_transfer_time is optional for all transfers where transfer_type is not 2. However, transfer_type = 3 and 4 are respectively "no transfers possible" and "in-seat transfer", which cannot be associated with any minimum time window.

Proposed Solution

Forbid min_transfer_time when transfers are not possible (transfer_type=3) or are in-seat transfers (transfer_type=4).

Type of change

GTFS Schedule

• Functional Change
• Non-Functional Change
• Documentation Maintenance

Proposed Discussion Period

We will leave this PR open one week for discussion, one week for review (minimum per governance). Then we will raise a vote to adopt this fix.

Proposal Update Tracker

Date	Update Description
(2026-10-19)	(Raised proposal)
(2026-10-19)	(Discussion period started)

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.

[skalexch]

Tagging @gcamp and @rudiejd for awareness since the last additions to min_transfer_time and transfer_type were #303 and #640