Strait of Gibraltar Map: Traffic Lanes, Currents and Reporting

A Strait of Gibraltar map shows a narrow neck of water between southern Spain and northern Morocco, about 8 nautical miles across at its narrowest point near Tarifa, connecting the Atlantic Ocean to the Mediterranean Sea. Overlaid on that geography is an IMO-adopted traffic separation scheme with an eastbound lane to the south, a westbound lane to the north and a separation zone between them.

More than 100,000 vessels a year pass through, which makes it one of the densest shipping corridors anywhere.

The traffic separation scheme and how to use it

The scheme keeps opposing streams apart. Eastbound traffic bound for the Mediterranean uses the southern lane, westbound traffic bound for the Atlantic uses the northern lane, and a separator zone runs between them. Precautionary areas sit at the eastern and western approaches where traffic converges.

Rule 10 of the collision regulations governs behavior inside the scheme. The obligations that matter most in Gibraltar are these:

• Proceed in the appropriate lane in the general direction of traffic flow.
• Keep clear of the separation zone, and do not use it as a passing lane.
• Join or leave at the termination of the lane where practicable, and at as small an angle as possible when joining from the side.
• Cross the lane, if crossing is unavoidable, on a heading as nearly as practicable at right angles to the flow.
• Avoid anchoring in or near the scheme.

A vessel of less than 20 meters, a sailing vessel or a fishing vessel must not impede the safe passage of a power-driven vessel following a lane. That rule is regularly tested here by small craft crossing to Morocco.

GIBREP: the mandatory reporting system

The mandatory ship reporting system for the Strait, known as GIBREP, entered force on 1 December 2010 under IMO resolution MSC.300(87). Participation is not optional for the ships it covers.

Reporting applies to all vessels of 50 meters length overall and above, and to smaller vessels using a traffic lane or separation zone to avoid immediate danger. Westbound traffic reports to Tarifa Traffic on VHF, eastbound traffic reports to Tanger Traffic, and the report covers ship identity, position, course, speed, cargo and any defect affecting maneuverability.

The two centres, one on each side of the Strait, exchange information. Reporting before entry rather than on the boundary makes the transit smoother, and vessel traffic services will pass traffic advisories that are worth having in poor visibility.

The current system that a map does not draw

The Strait carries two layers of water moving in opposite directions. Atlantic surface water flows east into the Mediterranean, replacing the volume lost to evaporation. Denser, saltier Mediterranean water flows west underneath it and out into the Atlantic.

For a ship that means a persistent eastgoing set at the surface, strengthened or weakened by tidal streams that run through the Strait on a semi-diurnal cycle. Slow vessels bound west can find themselves making very poor progress over the ground on an unfavorable tide, and passage planning should account for the tidal window rather than assume a steady speed made good.

Sea state changes fast as well. An easterly Levanter wind against the outgoing tide builds a short steep sea in the narrows, and a westerly Poniente does the same on the opposite phase. Visibility drops sharply in Levanter conditions when cloud forms over the Rock.

What a Strait of Gibraltar map does not show

The chart marks the lanes but not the traffic that ignores them. Three hazards dominate the watchkeeping picture:

• Ferry traffic. High-speed and conventional ferries cross the scheme almost perpendicular to it, running between Algeciras and Tarifa on the Spanish side and Tangier and Ceuta on the Moroccan side. They cross at speed and on schedule.
• Fishing activity. Fixed tuna nets and drifting fishing vessels operate on both approaches, some of them poorly lit.
• Small craft. Yachts, RIBs and unregulated craft cross the lanes without reporting and often without AIS.

Bunker and anchorage traffic adds to it. Gibraltar and Algeciras are among the busiest bunkering ports in Europe, so ships are constantly joining and leaving the stream at low speed. Cetaceans are abundant here too, and whale watching vessels congregate in the eastern approaches during the season.

Passage planning points for a Gibraltar transit

Load the current large-scale electronic navigational chart coverage and check that the traffic separation scheme and reporting boundaries are displayed rather than filtered out at your chosen scale. Set the GIBREP report as a marked waypoint task in the passage plan so the call is not forgotten during a busy watch.

Plan the transit for a favorable tidal stream where schedule allows, brief the bridge team on ferry routes and crossing angles, and keep the master informed at the point where traffic density rises rather than after the first close-quarters situation develops. The Mediterranean is a MARPOL special area for oil and garbage, so waste handling rules tighten as soon as the ship is through.

Sources and further reading

• IMO Resolution MSC.300(87): Amendments to GIBREP
• IMO Resolution MSC.63(67): Routeing measures
• Strait of Gibraltar Vessel Traffic and Shipping Trends - ShipInfo
• Gibraltar, Strait of - Oxford Public International Law

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