---
title: "Transport Department traffic speed (segment-level)"
method: GET
path: "/api/v1/data-gov-hk/traffic/speed"
tags: ["Public Finance & Government"]
---

# Transport Department traffic speed (segment-level)

`GET /api/v1/data-gov-hk/traffic/speed`

Segment-level traffic speed across the Hong Kong strategic road network, published by the Transport Department. Response contains per-segment speed observations, a validity flag (`Y` = observed, `N` = default / posted limit) and the TD IRN version. Sugra computes the mean speed across segments flagged valid. Upstream refreshes every two minutes; Sugra caches for five minutes.

## Response `200`

Per-segment speed observations across the Hong Kong strategic road network.

- EnvelopeTrafficSpeedPayload
  - `data` TrafficSpeedPayload, required — Response payload for `/api/v1/data-gov-hk/traffic/speed`.
    - `date_hkt` string, nullable — Upstream date stamp (HKT).
    - `time_hkt` string, nullable — Upstream time stamp (HKT).
    - `irn_version` string, nullable — Transport Department IRN (integrated road network) version.
    - `segment_count` integer, required — Total number of segments reported by upstream.
    - `valid_segment_count` integer, required — Number of segments reporting an observed speed.
    - `average_speed_kph` number, nullable — Mean speed across observed segments (kilometres per hour).
    - `segments` TrafficSegment[], required — Per-segment speed observations.
      - `segment_id` string, nullable — Transport Department segment identifier.
      - `speed_kph` number, nullable — Segment speed in kilometres per hour (None when upstream omits).
      - `valid` string, nullable — Validity flag (`Y` = observed, `N` = default / posted limit).
  - `meta` SugraMeta, required — Metadata attached to every /api/v1/* response envelope.
    - `endpoint` string, required — Requested endpoint path.
    - `data_time` string, required — ISO 8601 UTC timestamp of the source data, not of the request.
    - `response_time` string, required — ISO 8601 UTC timestamp when this response was produced.
    - `provider` string, required — API name and version.
    - `source` string, nullable — Identifier of the primary upstream source used for this response.
    - `attribution` string, nullable — Human-readable attribution mandated by an upstream source (e.g. a securities regulator or self-regulatory organization). Present only on responses whose source requires the owner and source to be clearly identified. Do not remove or alter it when using the response.
    - `fallback_used` boolean, nullable — True when the primary source failed and a fallback produced the data.
    - `fallback_chain` string[], nullable — Ordered list of sources attempted, in the order they were tried.
    - `cached` boolean, nullable — True when this response was served from the internal cache.
    - `stale` boolean, nullable — True when the cached response was returned after the upstream rate-limited or errored. Clients can use this to detect degraded data.

## Other responses

- `401` — Missing or invalid `x-api-key` header. JSON body with a stable `code` distinguishing `missing_api_key` (no header sent) from `invalid_api_key` (header sent, key not accepted); any other 401 source carries the generic `unauthorized` with its detail as `reason`. Plus `hint`. `plan` is always null on 401 - an unauthenticated request has no plan; quota exhaustion is 429, not 401.
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

---

[API](https://skmtc.net/sugra/apis/sugra-api.md) · [All operations](https://skmtc.net/sugra/apis/sugra-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/sugra/sugra-api/revisions/4c4530760ba1/schema)