Every PortTrip recommendation is built on three proprietary frameworks: the DIY Savings Index, the Ship-Safe Timing Buffer, and the DIY Difficulty Score. Here's exactly how each one works.
Last updated: May 2025 · Data covers 50+ cruise ports globally.
Cruise Port Independence Index · 2026 Edition
The score is a weighted average. Each input is 0–100; weights total 100%. Missing cost data produces limited_data and no score.
20% · transport Reliability
Reliability and clarity of transport between terminal and primary sights.
10% · distance
Penalty for long terminal-to-destination transfers.
10% · transfer Simplicity
Fewer required transfers score higher.
15% · tender Friction
Dock ports score higher; tender and cable-car queues reduce the score.
15% · time Sensitivity
How forgiving the return journey is when delays occur.
10% · walkability
Ease of reaching useful sights on foot or with simple local transport.
10% · cost Advantage
Savings percentage versus the comparable ship excursion.
10% · return Buffer Feasibility
Ability to retain the recommended return buffer in a normal full port day.
Methodology v1.0 · Published 2026-08-19 · Last updated 2026-08-19
The DIY Savings Index measures how much cheaper the independent alternative is compared to the median ship excursion price for the same destination. It's expressed as a percentage and a euro amount.
Formula
DSI = ((Ship Excursion Price − DIY Cost) / Ship Excursion Price) × 100
We take the median price of the top 3 most popular ship excursions to the same destination (typically: city highlights tour, historical site visit, and beach/leisure option). We check 4–6 major cruise lines per port annually. Prices are sourced directly from cruise line booking systems, not third-party aggregators.
DIY Cost includes: return transport from port to city centre (bus/train/taxi), entry fees to main attractions, and a mid-range lunch. It excludes shopping. Where a taxi is the only realistic option, we use local taxi rates — not tourist estimates. DIY Costs are updated seasonally (April and October).
72%
€95 saved
Rome (Civitavecchia)
58%
€70 saved
Barcelona
45%
€50 saved
Dubrovnik
The Ship-Safe Timing Buffer (SSTB) is our most conservative calculation. It determines the latest possible departure time from any attraction that still guarantees you're back at the gangway before all-aboard closes.
Formula
SSTB = All-Aboard Time − (Transit Time × 1.25) − 30 min gangway queue − 15 min contingency
Why ×1.25? Real transit takes longer than Google Maps suggests. Missed buses, passport queues, port security, and the occasional wrong platform all add up. We apply a 25% buffer to every transit time — then add another 45 minutes of fixed contingency on top.
Why 30 minutes for gangway queue? On busy port days (especially at Dubrovnik, Kotor, and Mykonos), returning passengers queue. We've seen 25-minute gangway waits on tender days. We build this in by default.
What happens in the planner? Every AI-generated itinerary enforces the SSTB. The app shows a live countdown to your "leave now" time. If you add a stop that pushes past the buffer, the app flags it.
⚠ Tender ports add extra buffer
For tender ports (Santorini, Kotor, some Dubrovnik itineraries), we add an additional 45 minutes to account for tender queues at both ends. Missing a tender is the same as missing the ship.
The DIY Difficulty Score (1–10) rates how hard it is to navigate a port independently. A score of 1 means anyone can do it with Google Maps. A score of 9+ means we'd recommend a ship excursion.
Transport clarity
How clear and reliable is the public transport from terminal to city?
Language barrier
How much does not speaking the local language impede navigation?
Walking difficulty
Does reaching the main sights require significant climbing or distance?
Time pressure
How tight is the itinerary relative to all-aboard time?
Crowd/queue risk
Do peak season crowds significantly reduce available time?
1–3
Easy
Solo-friendly, reliable public transport
4–6
Moderate
Doable with preparation
7–10
Hard
Ship excursion may be worth it
PortTrip actively flags ports where the DIY route is genuinely risky or poor value. This is not a hedge — it's our honest assessment based on difficulty score, timing constraints, and reported experiences.
Santorini
Cable car queues can hit 90 minutes in summer. Tender delays add another 45. On a 6-hour port call, DIY to the caldera is genuinely tight. We flag this.
Mykonos (tender)
Tender queues on cruise days can be 30–40 minutes. The old town is walkable once ashore, but the return trip is where people miss ships.
Kotor (tender)
The old town is beautiful and easy to walk. But tender days at peak season create 45-minute return waits. Don't cut it close.
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