International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 2

Number 4

December 2008

409

Human Errors and Oil Pollution from Tankers

P. Arsenie & R. Hanzu-Pazara

Constanta Maritime University, Constanta, Romania

ABSTRACT: The economical development of the world is based on transportation system. More than half of

the products transported all over the world are carried by sea. Sea transportation is made with different kind of

ships, as bulk carriers, cargo vessels, container ships, tankers. Ships are managed by people. In group or as

individual, anybody can make errors. In maritime area these errors have as results accidents and disasters.

Many of these events affect especially the environment. As 80% of necessary petroleum products are

transported by sea, the risk of a major environment disaster caused by human errors is high. Anyway, over

99% of petroleum cargo transported by sea is carried without incidents. This paper presents the effects of

human errors, mostly cases that involved tankers, which were produced in the navigation and operational

processes.

1 INTRODUCTION

Over the last 40 years or so, the shipping industry

has focused on improving ship structure and the

reliability of ship systems in order to reduce

casualties and increase efficiency and productivity.

We’ve seen improvements in hull design, stability

systems, propulsion systems, and navigational

equipment. Today’s ship systems are technologically

advanced and highly reliable.

Yet, the maritime casualty rate is still high. Why?

Why is it, with all these improvements, we have not

significantly reduced the risk of accidents? It is

because ship structure and system reliability are a

relatively small part of the safety equation. The

maritime system is a people system, and human

errors figure prominently in casualty situations.

About 75-96% of marine casualties are caused, at

least in part, by some form of human error. Studies

have shown that human error contributes to: 84-88%

of tanker accidents, 79% of towing vessel groundings,

89-96% of collisions, 75% of allisions. 75% of fires

and explosions.

Therefore, if we want to make greater strides

towards reducing marine casualties, we must begin

to focus on the types of human errors that cause

casualties.

A recent study of 100 marine casualties found

that the number of causes per accident ranged from 7

to 58, with a median of 23. Minor things go

wrong or little mistakes are made which, in and

of themselves, may seem innocuous. However,

sometimes when these seemingly minor events

converge, the result is a casualty. In the study,

human error was found to contribute to 96 of the 100

accidents. In 93 of the accidents, multiple human

errors were made, usually by two or more people,

each of whom made about two errors apiece.

But here is the most important point: every human

error that was made was determined to be a

necessary condition for the accident. That means

that if just one of those human errors had not

occurred, the chain of events would have been

broken, and the accident would not have happened.

Therefore, if we can find ways to prevent some of

these human errors, or at least increase the

probability that such errors will be noticed and

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corrected, we can achieve greater marine safety and

fewer casualties.

2 THE MARITIME SYSTEM: PEOPLE,

TECHNOLOGYAND ENVIROMENTAL

FACTORS

The maritime system is a people system. People

interact with technology, the environment, and

organizational factors. Sometimes the weak link is

with the people themselves; but more often the weak

link is the way that technological, environmental, or

organizational factors influence the way people

perform. Let’s look at each of these factors.

First, the people. In the maritime system this

could include the ship’s crew, pilots, dock workers,

Vessel Traffic Service operators, and others. The

performance of these people will be dependent on

many traits, both innate and learned. As human

beings, we all have certain abilities and limitations.

For example, human beings are great at pattern

discrimination and recognition. There isn’t a machine

in the world that can interpret a radar screen as well

as a trained human being can. On the other hand, we

are fairly limited in our memory capacity and in our

ability to calculate numbers quickly and accurately-

-machines can do a much better job. In addition to

these inborn characteristics, human performance is

also influenced by the knowledge and skills we have

acquired, as well as by internal regulators such as

motivation and alertness.

The design of technology can have a big impact

on how people perform. For example, people come

in certain sizes and have limited strength. So when a

piece of equipment meant to be used outside is

designed with data entry keys that are too small and

too close together to be operated by a gloved hand,

or if a cutoff valve is positioned out of easy reach,

these designs will have a detrimental effect on

performance. Automation is often designed without

much thought to the information that the user needs

to access.

Critical information is sometimes either not

displayed at all or else displayed in a manner which

is not easy to interpret. Such designs can lead to

inadequate comprehension of the state of the system

and to poor decision making.

The environment affects performance, too. By

“environment” we are including not only weather

and other aspects of the physical work environment

(such as lighting, noise, and temperature), but also

the regulatory and economic climates.

The physical work environment directly affects

one’s ability to perform. For example, the human

body performs best in a fairly restricted temperature

range. Performance will be degraded at temperatures

outside that range, and fail altogether in extreme

temperatures.

High sea states and ship vibrations can affect

locomotion and manual dexterity, as well as cause

stress and fatigue. Tight economic conditions can

increase the probability of risk-taking (e.g., making

schedule at all costs).

As you can see, while human errors are all

too often blamed on “inattention” or “mistakes” on

the part of the operator, more often than not they

are symptomatic of deeper and more complicated

problems in the total maritime system. Human

errors are generally caused by technologies and

environments which are incompatible in some way

with optimal human performance.

These incompatible factors “set up” the human

operator to make mistakes. So what is to be done to

solve this problem? Traditionally, management has

tried either to cajole or threaten its personnel into not

making errors, as though proper motivation could

somehow overcome inborn human limitations. In

other words, the human has been expected to adapt

to the system. This does not work. Instead, what

needs to be done is to adapt the system to the human.

The discipline of human factors is devoted to

understanding human capabilities and limitations,

and to applying this information to design

equipment, work environments, procedures, and

policies that are compatible with human abilities. In

this way we can design technology, environments,

and organizations which will work with people to

enhance their performance, instead of working

against people and degrading their performance.

This kind of human-centered approach (that is,

adapting the system to the human) has many benefits,

including increased efficiency and effectiveness,

decreased errors and accidents, decreased training

costs, decreased personnel injuries and lost time, and

increased morale.

3 HUMAN ERRORS IN TANKERS OPERATION

What do we mean by “human error”? Human error

is sometimes described as being one of the

following: an incorrect decision, an improperly

performed action, or an improper lack of action

(inaction). Probably a better way to explain human

error and their effects results in environmental

damage, as oil pollution is to provide examples from

two real marine casualties.

The first example is the grounding of the

TORREY CANYON. Again we have clear, calm

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weather this time it was a daylight transit of the

English Channel.

While proceeding through the Scilly Islands, the

ship ran aground, spilling 100,000 tons of oil.

At least four different human errors contributed to

this accident.

The first was economic pressure, that is, the

pressure to keep the schedule (pressure exerted on

the master by management).

The TORREY CANYON was loaded with cargo

and headed for its deep-water terminal in Wales.

The shipping agent had contacted the captain to

warn him of decreasing tides at Milford Haven, the

entrance to the terminal. The captain knew that if he

didn’t make the next high tide, he might have to wait

as much as five days before the water depth would

be sufficient for the ship to enter. This pressure to

keep to schedule was exacerbated by a second factor:

the captain’s vanity about his ship’s appearance.

He needed to transfer cargo in order to even out

the ship’s draft. He could have performed the

transfer while underway, but that would have

increased the probability that he might spill a little

oil on the decks and come into port with a “sloppy”

ship. So instead, he opted to rush to get past

the Scillies and into Milford Haven in order to make

the transfer, thus increasing the pressure to make

good time.

The third human error in this chain was another

poor decision by the master. He decided, in order to

save time, to go through the Scilly Islands, instead of

around them as originally planned. He made this

decision even though he did not have a copy of the

Channel Pilot for that area, and even though he was

not very familiar with the area.

The final human error was an equipment design

error (made by the equipment manufacturer). The

steering selector switch was in the wrong position:

it had been left on autopilot. Unfortunately, the

design of the steering selector unit did not give any

indication of its setting at the helm.

So when the captain ordered a turn into the

western channel through the Scillies, the helmsman

dutifully turned the wheel, but nothing happened.

By the time they figured out the problem and got the

steering selector back on “manual”, it was too late to

make the turn, and the TORREY CANYON ran

aground.

The second case presented is the grounding of

EXXON VALDEZ. The ship’s compliment

consisted of four deck officers (captain, chief mate,

second mate and third mate), four engineering

officers, one radio electronics officer, six able-

bodies seamen, three unlicensed engine personnel

and two cook/stewards. The vessel personnel in the

deck department stood two four hour watches each

day with eight hours off in between. All other

personnel were day workers. According with

international minimum safety manning for this ship

would be fifteen crew members (Exxon Valdez had

20 crew members when she grounded on Bligh

Reef).

Captain had been off the ship during the day she

was loading crude oil in Valdez port. Captain was

drinking that day. According blood analyses after

that his alcohol concentration was approximately

.285 at the time he boarded the ship, to do so without

showing some evidence of physical impairment or

needing some assistance. Additionally person

contacted after by the investigators reported none of

the EXXON VALDEZ crew members returning to

the vessel were under the influence of alcohol.

During the time the pilot was aboard the ship

Captain was off the bridge for approximately one

hour and thirty five minutes. The pilot smelled

alcohol on his breath.

Later on March 23rd, shortly prior to his relief,

the helmsman responded to an order from the master

to sail the ship 180

and put her on automatic pilot.

Helmsman was puzzled by this order. He didn’t

check it with the master. The master left the bridge

but not before asking the third mate, if he felt

comfortable sailing the ship under these conditions.

despite his limited experience in sailing the ship at

all, he replied that he did.

At 23:47 LT the ship left the Traffic Separation

Scheme going into the inbound lane to avoid the ice.

At 23:55 LT the helmsman was relieved. The ship

was on “load program up” which meant she was

increasing her speed while exiting the harbor. Thus,

EXXON VALDEZ was traveling at 12 knots and on

automatic pilot just prior to hitting Bligh Reef.

Putting the ship on automatic pilot in confined

waters and not telling the third mate the master had

done so was extremely inconsistent with normal

practice. At his relief, the helmsman reported to the

third mate that the ship was on automatic pilot,

something the third mate did not know about. The

third mate did not discuss the reason for the

automatic pilot with the master.

The third mate holds a second mate’s license, and

first sailed as the third mate on an Exxon tanker in

January, 1987. He had sailed on five tank vessels

owned by the company and had been employed by

Exxon for nine years. He had completed

approximately 18 voyages in and out of Valdez,

sailing in both unlicensed and licensed categories. At

the time of the grounding he had approximately 199

days of at sea experience as a third mate.

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The night before he slept 6 hours, then after lunch

had a cat nap and relieved the chief mate for supper

and worked through to the grounding. The third mate

had only about a year’s experience as a deck officer.

The situation is further complicated because the

chief mate had worked the entire time of the loading,

was asleep, and was unavailable as an additional

resource. In addition to his bridge duties, the cargo

is the primary responsibility of a chief mate in

the Merchant Marine. This includes loading and

discharge of cargo could only be conducted by the

second and third mate on duty, the chief mate is

normally on hand when loading and discharging are

started and concluded. The ship left port at about

21:00 LT.

The third mate decided not to call his relief, the

second mate, until after they cleared the ice. The

third mate determined there was .9 mile between

Busby Island and the ice floe and felt he could pass

around the ice. The master left the bridge at 23:52

LT. the third mate relied considerably on the radar,

but did not correlate the radar information with the

navigation charts through position fixing. The

submerged reef was not displayed on the radar.

According with bridge organizational manual

used by Exxon, in this situation is stated that two

officer be on bridge during this transit. The chief

mate was sleeping. Some time before midnight the

third mate put the ship in hand steering condition. At

the same time he plotted the ship as 1.1 miles from

Busby Island. Before midnight the AB reported a red

light flashing

every

five

seconds to

the third mate.

He acknowledged her and stated that he knew the

light to be Bligh Reef. The third mate ordered a right

10 degree rudder but the vessel did not move to this

position. There is a six minute delay before the third

mate and helmsman respond to the fact that the ship

did not begin to turn.

About this time the AB reported the light flashing

every 4 seconds on the wrong side of the ship. Now

the third mate order a right 20 degree rudder.

Moving at 12 knots while the ship was still engaged

in maneuvering evolutions to avoid ice violated

prudent ship handling practices while increasing risk

of damage to the ship if ice floes had been struck. He

then orders hard right rudder.

When the ship hit the reef the third mate ordered

a hard left rudder to get the ship to stop swinging to

the right and prevent the stern from swinging

around. The ship had clearly skidded into Bligh

Reef. The helmsman was confused about some

aspects of the situation. He also reported that the

third mate was panicky. The chief engine stop the

engine at 00:20 LT.

For about 45 minutes the master tried to get the

ship off the reef, probably moving from dead slow

ahead to full ahead, and finally slowing down and

stop. The chief engineer had advised the master not

to move the ship. Vessel Traffic Service had advised

to move cautiously. The company declared that the

master was not trying to get the ship off the reef

because he never put the ship astern.

The chief mate was awakened by the grounding.

He went to the cargo control room to assess the

damage. He determined that the stress on the ship

exceeded acceptable limits and took this information

to the master. The chief mate performed further

analyses and concluded that if the vessel were not

supported by the reef it would capsize. He relayed

this information to the master who, for an additional

half hour tried to get the ship off the reef.

In this case, like in the first presented, a amount

of human errors concurred to the disaster. The errors

are from the area of navigation and ship characteristics

acknowledgement, bridge management regulations,

communication’s on bridge and on board the ship,

crew competencies.

Below we’ll try to show some of these errors,

according with facts and regulations applied for this

situation.

A number of dynamics occurred on the bridge.

The first is that the two key players aren’t there. The

company manual stated that the master or chief mate

must be on the bridge while exiting port and the law

requires a first class pilot’s license or endorsement

for the waters. The situation warrants the added

responsibility of the master to be on the bridge, not

the chief mate during loading and discharging

operations. Sufficient redundancy might have been

in the system if one of these people had acted as a

second pair of eyes for the third mate. Second, no

one checked the reasoning behind orders. From this

account we don’t know if the helmsman may have

had reason to question the situation (gyro, load

program up conditions). The AB may have

questioned in his mind what they were doing. If he

did he didn’t find a way to direct attention to that

question without putting himself in danger of

incurring the third mate’s wrath.

Overall, one might suspect this kind of

unprofessional seamanship on the part of the captain,

the third mate and the helmsman had occurred

before. Such behaviors usually don’t emerge full

blown, they grow over time. There is sufficient

evidence from the company that the captain had

problems managing people and there is some similar

evidence that the third mate found it difficult to keep

supervisors informed about what he was doing.

There is nothing that indicates training or a culture

that values open communication among bridge

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personnel. An appropriate culture of safety and

vigilance seems not only to have been in place. The

watch cycles (4 on, 8 off, 4 on, daily) seems an

inherent part of the organization.

Looking at the performance evaluations of the

helmsman, it is clear he was not very competent. A

master should not leave the team of an incompetent

helmsman and a third mate with little experience to

run a tanker through an ice field. In this case the

pulls and pushes on the master lead to his failing to

think about this issue.

The EXXON VALDEZ didn’t operate in isolation

from the relationships various participants had with

one another. The pilot smelled liquor on the master’s

breath and didn’t report it to anyone. The

relationship between pilots and master’s is sensitive,

and the pilot’s job future is an important respects

depends on what the master thinks of him. Through

this relationship seems cast in stone it may well be

time to examine it thoroughly. Similarly, the

relationship of the VTS at Valdez and the EXXON

VALDEZ was one of very little attention even to the

giving of advice. This kind of quasi advice only

versus direction issue must be looked at in both

cases.

Crew aren’t in place for the operation of a culture

which stresses the existence of risk and risk

avoidance. They aren’t in place for good

communication among the parties, they may not be

in place for engaging in good training which can

help the bridge team interact appropriately. In

addition, if anyone in the bridge group was not

competent, the rewards are not in place for getting

rid of that person or retraining him.

4 CONCLUSIONS

We have seen that human error (and usually multiple

errors made by multiple people) contributes to the

vast majority (75-96%) of marine casualties, making

the prevention of human error of paramount

importance if we wish to reduce the number and

severity of maritime accidents. Many types of human

errors were described, the majority of which were

shown not to be the “fault” of the human operator.

Rather, most of these errors tend to occur as a

result of technologies, work environments, and

organizational factors which do not sufficiently

consider the abilities and limitations of the people

who must interact with them, thus “setting up”

the human operator for failure. Human errors can

be reduced significantly. Other industries have

shown that human error can be controlled through

human-centered design. By keeping the human

operator uppermost in our minds, we can design

technologies, work environments, and organizations

which support the human operator and foster

improved performance and fewer accidents.

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Perrow C. 1984 Normal Accidents: Living with High-Risk

Technologies.

Wagenaar W.A. & Groeneweg J. 1987 Accidents at sea:

Multiple causes and impossible consequences.

Hanzu-Pazara R. & Bocanete P. 2006 The influence of team

error in maritime industry, Transport Book of Constanta

Maritime University Navigation Dept, no. 4.

Reason J, 1990 Human errors.