MAIB: Bunker Saving Vessel Design Led to Ship Collision

The City of Rotterdam's bunker saving hull shape was found to have caused "relative motion illusion."

A report released by the UK Government's Marine Accident Investigation Branch (MAIB) last week has concluded a December 3, 2015 collision between the Panama-registered pure car carrier City of Rotterdam and Danish-registered RoRo ferry Primula Seaways on the River Humber was caused by the shape of the car carrier's fuel efficient hull design.

"City of Rotterdam's hemispherical bow was designed to reduce wind resistance and carbon emissions and to provide better fuel economy. A consequence of the bow's shape was that the vessel's bridge was of unconventional design," states the report.

The bridge design, which causes an "off-axis window on perception," is said to have resulted in a "relative motion illusion" that led to the collision.

"The effect of standing at an off-axis window is that the observer loses all sense of orientation relative to the ship. Objects in the scene are positioned relative to the observer, including relative motion. The consequence of this for navigation is that objects are considered to move as though the ship were headed in the direction of the window," explains the report.

Intervention to avoid a collision with Primula Seaways by City of Rotterdam's master was too late, while challenges to the pilot's actions by Primula Seaways' bridge team and the Humber Vessel Traffic Service were called "insufficiently robust."

Both vessels are noted to have sustained damage from the collision, but were able to make their way to Immingham under their own power, with no pollution and no serious injuries reported.

"Feedback from a number of pilots based in several ports frequently visited by City of Rotterdam and City of St Petersburg indicated that they found piloting the vessels 'disconcerting' or 'uncomfortable,'" explained the report of the car carrier and its sister vessel.

However, those pilots are noted to have developed strategies to cope with the challenges posed by the bridge layout, including standing behind the centreline compass repeater or the helmsman, limiting time at the navigation workstation, and using hand-held VHF radios.

The report recommends that Bureau Veritas S.A. (BV), City of Rotterdam's classification society, should propose measures to the International Association of Classification Societies to raise awareness of relative motion illusion and promote the requirement for naval architects and shipbuilders to adhere to decided upon ergonomic principles for bridge design.