Gibraltar

Open·Constraint: The Strait of Gibraltar is constrained by geography rather than draft: the passage narrows between…·Alternative: None recorded

The passage stays open; navigation is ordered around what cannot safely cross at once.

What constrains it

The Strait of Gibraltar is constrained by geography rather than draft: the passage narrows between southern Spain and northern Morocco, while Atlantic water entering the Mediterranean meets Mediterranean water flowing out below it. That exchange creates opposing currents, and the surrounding headlands can bring strong winds and difficult sea conditions. The International Maritime Organization's traffic-separation arrangement treats the crossing as a navigation problem, not a capacity auction (IMO, accessed September 16, 2026).

Rationing mechanism

No rationing mechanism is in force for the open passage. Ships do not receive auctioned slots, convoy places, or a commercial licence to cross. The IMO's GIBREP system requires participating vessels to report their movements to shore authorities, while the traffic-separation scheme assigns lanes and keeps crossing traffic from turning the narrow waterway into an unmanaged meeting point (IMO, accessed September 16, 2026).

Incidence

Ship operatorsMasters must plan around opposing currents, traffic lanes, wind, and reporting requirements, which can raise fuel use, navigation workload, and the cost of delays.

Port operators at Algeciras and TangierTerminals on either side absorb disruption when difficult conditions or a safety intervention slows the arrival sequence of ships and cargo.

Marine insurersInsurers carry the cost of accidents and pollution in a confined, heavily used waterway, even though the passage itself remains legally open.

Spain and MoroccoTheir maritime authorities must fund and operate reporting, traffic coordination, and navigational safety measures without controlling every vessel's right of transit under the international-law regime for straits.

Comparable passagesGibraltar differs from a slot-rationed passage because safety authorities organize movement without deciding who may buy access; who decides remains the most useful comparison.