Why can IDO ferries be cancelled in calm weather?

Calm-looking weather does not guarantee that a ferry will run. In Sefer İptal’s selected weather-study sample, 204 of 10,556 sailing records meeting strict calm-weather criteria were cancelled (1.93%). Local reports reproducing IDO lists give a schedule-change or technical reason for 52 of those cancellations. This is a bounded case study of why weather alone cannot explain every cancellation, rather than a breakdown of causes across all sailings.

Study period: 1 January 2022–31 August 2026. News links were rechecked on 17 September 2026. This article is not a current cancellation list or a risk estimate for today’s ferry.

Which sailings and which weather criteria?

The weather-study sample contains 96,260 records and 4,703 cancellations. It is a research cohort excluding conflicting statuses and selected prolonged cancellation runs; it does not represent every IDO sailing or the entire archive. The strict screen requires maximum sampled wind ≤3 m/s, gust ≤5 m/s and wave height ≤0.3 m, with zone temperature 18–30 °C, hourly precipitation ≤0.1 mm and low cloud cover ≤30%. Missing inputs do not pass. These thresholds are not maritime operating limits.

The previous-six-hour check additionally requires zone wind ≤5 m/s, gust ≤8 m/s and waves ≤0.5 m. It does not reconstruct what the operator knew when deciding. The 204 strict-screen cancellations represent 4.3% of the study’s 4,703 cancellations; that answers a different question from the 1.93% rate above.

What does matching the news establish?

The initial manual review searched 40 Turkish queries for 16 dates chosen for large clusters and coverage across years and routes; the selection was not random. Those dates contained 97 cancellations meeting the strict screen. We then checked every departure listed in the three identified articles, allowing matches outside the initial date selection. The table below covers all 204 strict-screen cancellations.

Of the 148 without an exact match, eleven fall only within a broader route/date-range report. We do not add them to departures with an exact technical-reason match. Matching date, directed endpoints and time also does not verify a vessel identity or operator voyage identifier: those identifiers are absent from the reports.

What did the three dated reports contribute?

Yalova Hayat’s 22 May 2026 report reproduces lists for 24–31 May. We used 89 parsed notices rather than the headline’s 90; the text contains both schedule-change and weather reasons. Its 21 November 2025 report combines an earlier date-range account with timed departures for subsequent days; we kept those evidence levels separate. Yalova Güncel’s 6 July 2026 report lists Pendik–Yalova departures with technical reasons. These are secondary publications attributing the notices to IDO, not preserved original official notices.

Why retain the four explicit weather explanations?

We did not relabel a reported weather cancellation as technical or schedule-related simply because our sampled values were mild. Weather inputs are retrospective model outputs sampled at the UTC hour at or before departure, not a verified archive of forecasts issued when decisions were made. Pendik–Yalova and Kadıköy–Bandırma use approximate offshore endpoints plus a midpoint; other routes use a zone point. This does not follow every point of a vessel’s actual track. Visibility, currents, terminal conditions and weather elsewhere are not established by this screen.

What cannot be inferred from calm-weather data?

A schedule-change explanation does not establish why the timetable changed. A technical explanation does not identify a particular fault. This study has no evidence for low ticket sales, holidays, political decisions or maintenance as the underlying explanation. Final sales snapshots do not measure demand before the decision. An unmatched cancellation is not proven false or erroneous. Prolonged cancellation runs alone do not establish an official route closure. These shares depend on sample selection, route mix and period; they offer no guarantee for today’s sailing.

What should a passenger do?

Check the reported status for the date, time and direction on your ticket, and confirm with the operator before travelling, even when a weather app shows sunshine. Open the live sailing search or follow the cancellation-checking steps. For whole-archive figures, read 2018–2026 cancellation statistics; for scope and attribution, see data sources.

Sources and data

İDO: official sailing and ticket information · MGM: Marmara marine forecast

Data methodology and scope