Bugs, Fixes, Apologies, and Corrections

Between September 2 and September 20, the MARTA fail / ATLTransit.live alert accounts I run posted 38 service alerts that were corrupted, this comprised less than 1% of total posts.

This happened due to a bug in the logic that manages text received from MARTA’s service alerts emails. This bug caused data to be corrupted when sent to an LLM-based (AI) process that prepares service alert messages to be sent via Bluesky.

The root cause of the bug has been fixed, and additional safeguards have been implemented to prevent this issue from occuring again. Additionally, the LLM-based process has been strengthened to fail correctly when corrupted data is processed.

What it looked like

A Bluesky user flagged this one, which is what started the investigation:

Gold Line trains are not running between Indian Creek and Georgia State stations. Use bus shuttles or seek alternate transportation.

The Gold Line doesn’t serve Indian Creek or Georgia State, of course. Those are Blue Line stations.

The email MARTA actually sent was four routine Route 22 bus trip cancellations. Nothing about trains, nothing about a suspension, no shuttle buses.

Deleting invalid posts on the Bluesky accounts

The posts containing incorrect data are, as of this post, being deleted. A table of the incorrect posts are included at the bottom of this post. I’m deleting instead of editing because Bluesky does not have the capability to edit posts. Inserting edited posts into the timeline would create the false impression that the now-edited alert is a new alert, when it is not.

Why (groan) LLMs/AI are used to process alerts - technical explanation

MARTA Service Alerts are text-based alerts that do not follow any standard template. A canceled bus dispatch, a delayed rail line, etc.: these are written by humans using different syntax, grammar, and formatting.

A couple years ago, when I started this project, LLMs were not yet practical, and I used hard-coded rules with Natural Language Processing (NLP) techniques to parse components of these text messages. However, there were too many text variations, and I was continuously creating increasingly complex rules to parse the messages.

LLMs, however, can parse messages into structured data. This used to be an expensive service, but has become cheaper and more accurate as of late.

Accordingly, the pipeline that processes MARTA service alerts submits, processes, and prepares text for publishing in Bluesky. (Often, MARTA service messages exceed the max 300 characters of Bluesky and require reformatting.)

What’s next

Obviously, I’m disappointed that bad data was posted to Bluesky. MARTA.fail (now ATLTransit.live) is a hobby project that is only useful if y’all trust the outputs that the project creates. I learned quite a bit from digging into what broke, and I’m hopefully that this will mitigate future errors.

I’m also independently reviewing the published alerts - more carefully in the next few days, and regularly after that, to ensure we don’t see this type of issue in the future. The code processing the alerts also has more fail-safes that work to prevent publishing any incorrect or incomplete information to the Bluesky alerts.

And, thank you to the Bluesky users who let me know of this issue.

And finally…

MARTA still publishes its service alerts ONLY to Twitter, and not to any other platform, RSS feed or other open source-type data feed. (MARTA does publish service alert-related data to its “GTFS-RT” data feeds, but that’s not available in a readily available human-friendly format).

In the year 2026 in the City of Atlanta, it’s completely unacceptable for a public entity such as MARTA to publish critical information solely to a microblog site operated by a trillionare racist lunatic.

While MARTA does allow sending service alerts via Email and text, the signup process is clunky, the alerts verbose, and will quickly fill up any email box or messages folder.

I created this hobby service so that I could view a quick feed of the latest alerts without having to scroll through my email box or otherwise jump through hoops to get the most basic information about MARTA service disruptions. Going forward, I hope to provide this service with fewer errors going forward.

-Michael ([email protected])

Table of incorrect posts

Every incorrect message below, with the accounts it reached. None of these were issued by MARTA. Times are Eastern.