Mark images in Service Alerts as final

[gcamp]

Summary

image, image_alternative_text and the TranslatedImage message have been in the spec since September 2021. This PR removes their experimental tag.

Type of change

GTFS Realtime

• Specification Change

Proposed Discussion Period

7 calendar day (minimum)

Testing Details

• Consumer(s): Transit
• Producer(s): Metro Transit (Minneapolis), TransLink (Vancouver), MBTA (Boston), VTA (Bay Area), Mecatran.

One caveat on the consumer side: Transit parses both fields and can display the image alongside the alert, but it isn't enabled by default today — it has to be manually enabled for the image to be shown to riders. There's plans to show it by default in the future. In the list of producers, we currently only show Metro Transit and TransLink.

Minneapolis	Vancouver

Proposal Update Tracker

Date	Update Description
2026-07-29	Initial PR submission

[ckraatz]

+1 from SimplifyTransit when you're ready for a vote. Our Alerts module has been publishing the Image field since 2022 because map images are very helpful for riders. Our Subscriptions module also consumes images and embeds images when sending Alerts via email/SMS, so we support this field from a consumer side too.

I would encourage Producers to ensure there's a requirement to include good Alt Text for accessibility. It's important to always describe what's in the image, even if the image is a map that can't be fully described in words and its contents are accessibly represented in text in the Header/Description fields. We don't allow Images to be uploaded without entering Image Alt Text, so that field is "conditionally required."