Data & methodology

Every number on this site comes from an identified source with a stated cadence.

Sources

WSDOT Traveler API (official). Live sailing space, terminal directory, and schedules come from Washington State Ferries' public developer API, accessed with a registered key and an identified user agent. Attribution: Data source, WSDOT Traveler API. Vessel positions and actual departure times come from the same API's vessel-tracking feed, checked on the same cadence, and power the lateness notes on the board and the departure-time archive. WSDOT updates sailing space as often as every 5 seconds; we check once a minute, well below the feed's update rate, and every number carries the freshness stamp you see on the board.

Published opening dates. Reservation-opening reminders are built from dates operators announce publicly. No scraping is involved.

Field definitions (drive-up, reservable, dashes, capacity) are described on the how it works page.

Known limitations

Live space reflects the operator's terminal systems and can shift between our check and your arrival. A dash in a count column means the operator isn't displaying that space type for the sailing, which is different from zero. Sailing history begins the day our archive started; charts state their observation window.

Contact

Questions about the data, including from operators, reach a monitored inbox: hello@ferrysignal.com.