Add a Code of Conduct

README.md

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 This repo exists to host public/open items related to the broad community of all TDC stakeholders: both direct and would-be participants, including data users, providers, funders, and others.
 These items include:
 
-- [Discussions](https://github.com/orgs/transport-data/discussions) —the discussions for the [transport-data GitHub organization](https://github.com/transport-data) are attached to this repository.
+- ``doc/`` —documents and information about the TDC itself. These:
+  - …are stored in Markdown format; versions in other formats are derived from the Markdown versions.
+  - …represent the latest/official text of each document.
+  - …have different status, described in each document. For example, some are ‘policies’ and part how TDCI self-governans; others are for information only.
 - [Issues](https://github.com/transport-data/community/issues) —specific, actionable TODO items, bugs, requests, etc.
-- [Wiki](https://github.com/transport-data/community/wiki) —for static information, editable by all.
+- [Pull requests](https://github.com/transport-data/community/pulls) are used to propose and discuss revisions to these documents.
 
 Elsewhere:
 
-- [transport-data/org](https://github.com/transport-data/org) has closed/internal items for the TDC Initiative core participants.
+- [transport-data.zulipchat.com](https://transport-data.zulipchat.com) —a [Zulip](https://zulip.com) organization including private channels for TDCI stakeholders.
+- [transport-data/org](https://github.com/transport-data/org) has closed/internal items for the TDC Initiative “core group” of founding participants.
 - [transport-data/tools](https://github.com/transport-data/tools) is the main repo for code and tools that handle TDC-related (meta)data.

doc/code-of-conduct.md

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+# Code of conduct
+
+This document is a **TDCI policy**.
+It is in a **draft** state; to leave comments, see [this pull request](https://github.com/transport-data/community/pull/75).
+
+## Introduction
+
+The shared mission of the Transport Data Commons Initiative (TDCI) is to **make high-quality transport data accessible to all** by building the Transport Data Commons (TDC).
+This mission is pursued through the contribution and cooperation of many, diverse people from around the world.
+We believe our communities of contributors should be as diverse, inclusive, and accessible as possible;
+this in turn means they must be positive, safe, and healthy environments for anyone who joins (and wants to join) them.
+By ensuring these things, we can enable all who contribute to and benefit from the TDC.
+
+This **Code of Conduct** focuses on the behaviour of individual TDC participants.
+The word ‘participant’ is deliberately broad. it includes everyone who:
+- provides data, metadata, code, or text via the TDC Portal, TDC code repositories, or other venues;
+- accesses or uses any of the above;
+- offers feedback, feature requests, or other input on the activities of the TDCI or any other participant;
+- joins TDCI events or meetings, whether in person or online;
+- makes material contributions, e.g. of funding or other resources, to TDCI.
+
+## Expected behaviour
+
+We expect all TDCI participants to:
+
+- **Show respect** for one another.
+- **Practice empathy** towards other participants.
+  Understand that they may come from a different background,
+  with respect to gender; age; language; national, ethnical, or religious affiliation; physical or mental disability; class or caste; and career, disciplinary, or professional experience.
+  Seek to understand pa
+- **Act with civility and collegiality**;
+  assume good faith and constructive intent.
+- **Recognize and credit** contributions made by others.
+- **TODO** expand this list.
+
+## Inappropriate and unacceptable behaviour
+
+Generally, departure from the expected behaviour is not appropriate.
+Some specific kinds of inappropriate behaviour include:
+
+- **Harassment** of any other TDCI participant.
+- **Content vandalism and abuse of the TDC**.
+  This includes deliberately introducing biased, false, inaccurate or inappropriate content,
+  or hindering, impeding or otherwise hampering the creation (and/or maintenance) of content.
+- **TODO** expand this list.
+
+### Consequences
+
+In order to keep the TDCI communities safe and accessible for all participants,
+the TDC Core Group will take any action necessary to discourage or stop the actions of any participant who violates this code of conduct.
+This may include blocking their interaction with the TDC online resources or in TDC events.
+
+## Revisions of this document
+
+2026-05-06 First draft
+

doc/reference.md

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+# References
+
+This document is **informational** only.
+It contains links to information related to TDC.
+
+## Codes of conduct
+
+- [Python Software Foundation](https://policies.python.org/python.org/code-of-conduct/).
+- [Wikimedia](https://foundation.wikimedia.org/wiki/Policy:Universal_Code_of_Conduct).
+
+## Organizations
+…and agencies that work with transport data.
+
+- [MobilityData](https://mobilitydata.org) maintains the GTFS and operates https://mobilitydatabase.org

doc/use-of-ai.md

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+# Use of ‘AI’ with/on TDC
+
+This document is **informational**.
+
+## Introduction
+
+“Artificial intelligence” or ‘AI’ is a broad umbrella term that can encompass, among other things:
+1. Applications of machine learning (ML) such as large language models (LLMs).
+2. Systems and software built on (1).
+3. Companies and organizations that create (1) or (2).
+4. A domain of research about the methods underlying (1).
+5. Behaviours of people in (3) such as data collection, training, marketing, etc.
+6. Behaviours of users of (2).
+
+This document offers clarification for people considering whether and how to use ‘AI’ as they participate in the TDC.
+
+In general, people who choose to use ‘AI’ as they participate in the TDC are nonetheless TDC participants.
+This means that the TDC Code of Conduct applies to their behaviour.
+The participant is fully responsible for the outputs or effects of any ‘AI’ they choose to use; if these outputs or effects mean that the participant violates the Code of Conduct, ‘AI’ use is no excuse or exemption.
+
+Current (2026) ‘AI’ systems have particular failure modes that could lead to Code of Conduct violations. These include:
+
+- Output based on TDC (meta)data introduces subtle errors into those (meta)data,
+  including mislabeling, incorrect categorization, dropped or ‘phantom’ data points,
+  changed observation values, malformed/non-standard content presented as standards-compliant.
+- Output based on TDC (meta)data fails to credit the appropriate upstream source(s), TDC curation: by omitting citations, including non-existent citations, citing the wrong source(s), or some combination of these.
+  in particular that it does not introduce false, misleading, or 
+- Output based on TDC (meta)data is falsely presented as being “by” TDC, TDCI, or any other participant.
+- **TODO** expand the list.
+
+Some practices that can help avoid harms, code of conduct violations, and consequences:
+
+- **Proactively disclose intent** to use ‘AI’.
+  - Identify the systems and software to be used, and how they will be used.
+  - Obtain consent from the people whose work will be given as input to ‘AI’.
+    Respect their right to decline or withhold their work.
+- **Carefully check output** from ‘AI’.
+  Ensure that you do not violate the CoC by forwarding text, data, or code that is false, misleading, fails to duly credit original authors, or violates copyright or license conditions.
+- **Clearly label output** from ‘AI’.
+  Ensure that any other TDC participant who interacts with ‘AI’ outputs you produce is aware of how that content was produced. 
+
+## Revisions of this document
+
+2026-05-06 First draft