Connect Japan Road Traffic Volume to Codex
Query Japan Road Traffic Volume directly from Codex. Arlet links the two through one MCP connection and takes care of API keys.
This server connects your AI client to the Traffic Volume API, operated by the Japan Road Traffic Information Center (JARTIC) for the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). It serves directional vehicle counts measured by roughly 2,600 permanent traffic counters (loop/ultrasonic and CCTV-AI counters), mainly on national routes (一般国道).
Key features:
- Query by bounding box and observation time (JST), at 1-hour or 5-minute aggregation.
- Each observation point returns its coordinates, point code, and up/down direction counts split into small vehicles, large vehicles and unclassified, with missing-data flags.
- Retention: about 3 months for hourly values, about 1 month for 5-minute values.
Usage notes: the values are reference values, not official MLIT survey results, and the terms of use require the attribution shown in every response (this server includes it automatically). Query area per request is capped to roughly a city-sized bounding box to respect the API's fair-use rules.
How to connect Japan Road Traffic Volume to Codex
- 1
In the Arlet dashboard, open Data tools, find Japan Road Traffic Volume and switch it on. No API key setup is needed.
- 2
In your terminal, run codex mcp add arlet --url https://mcp.arlet.dev/mcp/ to add Arlet as an MCP server.
- 3
Codex detects OAuth support and opens your browser. Sign in with Google and click Allow on the consent screen.
- 4
Once connected, both the CLI and the IDE extension can call Arlet tools (the configuration is shared).
If the browser does not open, run codex mcp login arlet to redo the authentication.