Retrieve speed restriction data for a line on a given date.

Parameters for the /api/speed_restrictions endpoint.

Attributes: line_id: Line identifier (e.g., Red, Orange). date: Date to query (YYYY-MM-DD).

Response for /api/speed_restrictions — speed restriction zones.

Attributes: available: Whether speed restriction data exists for this date. date: Actual date of the data (may differ from requested date). zones: Speed restriction zone details, if available.