INVESTIGATIONS INTO ENHANCED ALERT MANAGEMENT

FOR COLLISION AVOIDANCE IN SHIP-BORNE INTEGRATED

NAVIGATION SYSTEMS

Michael Baldauf

, Knud Benedict

World Maritime University Malm

Hochschule Wismar University of Technology, Business and Design, Department of Maritime Studies Warnemünde

Sweden

Florian Motz, Sabine Höckel

Research Institute for Communication, Information Processing and Ergonomics, FGAN, Wachtberg, Germany

Keywords: Human Computer Interaction, Human Machine Interface, Alert Management, Collision Avoidance,

Intelligent Collision Warnings, Integrated Navigation Systems, Bridge Alert Management, e-Navigation.

Abstract: High sophisticated integrated navigation systems are installed on the ship navigational bridges to support

the operator of modern container ships. The integrated systems should assist the captains, navigation

officers and the pilots to avoid any dangerous situation when sailing from port of departure to the port of

destination. Numerous Human Machine Interfaces require interaction to control the voyage in every

situation under all possible circumstances. However, with respect to shipping statistics collisions and

groundings are major risks. This paper deals with investigations into the alert management on board modern

ships and potential approach to reduce the number of alarms. Results gained during several field studies on

board ships are presented. Based on these results the draft of a concept for reducing the high frequency of

collision warnings to be implemented into the navigation systems on board is discussed. First preliminary

results are introduced.

1 INTRODUCTION

In February 2008 the Norwegian classification

society Det Norske Veritas (DNV) published new

statistical figures on sea accidents. The figures

clearly showed that the number of accidents has

doubled over the last five years. DNV concluded

that this is caused mainly by the continued growth of

the world fleet and a shortage of officers with right

skills. On the other hand, technical failures were

mentioned more seldom.

It can be seen as another sample for Ironies of

Automation as described by Bainbridge (1983) –

that the majority of total losses in shipping is due to

collisions, groundings and contacts although there

are highly automated systems installed onboard

seagoing vessels to support the Officer of the Watch

(OOW) on the ships navigational bridge. Especially

with respect to the level of integration of the sensors,

equipment, displays and assistance systems those

navigational bridges can undoubtedly be defined as

highly-complex man-machine systems. Sherwood

Jones et al. (2006) discuss the management of alarm

systems and come to the conclusion that the role of

the OOW seems to become more an observer of the

navigational equipment instead of their situation

awareness being improved by such systems.

Recent field studies (Motz, Baldauf & Höckel,

2008) showed a lack of alert management. There are

superfluous alarms from several systems under

conditions of high traffic density especially in sea

areas near the coast and at harbour entrances. With

respect to implemented collision warnings there is a

lack of adjustment of the thresholds. In order to

better and effectively support the mariner onboard a

task- and situation-dependent representation of

encounter situation's parameter and information

basing on sufficient acquisition of reliable data and

169

Baldauf M., Benedict K., Motz F. and Höckel S. (2009).

INVESTIGATIONS INTO ENHANCED ALERT MANAGEMENT FOR COLLISION AVOIDANCE IN SHIP-BORNE INTEGRATED NAVIGATION

SYSTEMS.

In Proceedings of the 11th International Conference on Enterprise Information Systems - Human-Computer Interaction, pages 169-174

DOI: 10.5220/0001954401690174

 SciTePress

its processing is an urgent demand and an actual

challenge for research and development.

To approach the problem a number of field

studies were performed on board of ships to

investigate the situation with respect to the

occurrence of alarms and their handling by the

bridge team. Based on the outcome of these studies

lacks and shortcomings of navigation systems

presently in use were identified and an approach to

reduce the number of false alarms is developed as

suggestion, taking into consideration available

technical system as e.g. ARPA (Automatic Radar

Plotting Aid) and AIS (Automatic Identification

System) information as well as new GNSS (Global

Navigation Satellite System) facilities. Within this

paper the used methods and selected results for

samples of the investigations are presented.

The investigations were performed under the

framework of two national research and

development projects funded by German Federal

Ministry of Education and Research and the German

Federal Ministry of Transport, Building and Urban

Affairs. The results of the studies are used to directly

support the work of the International Maritime

Organization regarding the development of new

performance standards for Bridge Alert Management

and to contribute to the further development of the e-

Navigation concept.

2 ONBOARD COLLISION

AVOIDANCE – PRESENT

SITUATION

As illustrated in the following figure the process of

collision avoidance in principle consist of three main

elements: "Situation Assessment", "Decision

Finding" and "Initiating and Control a measure to

avoid a dangerous encounter".

Figure 1: Simplified model of the on board process of

collision avoidance.

During the process of situation assessment the

OOW has to evaluate and assess the results of his

permanent observations in order to detect any risk of

collision with other objects in the vicinity of his own

ship. Today the additional information provided by

AIS contributes to better situational awareness as it

widely solves e.g. the problem of clear target

identification. In case of a situation with developing

or existing risk of collision, the OOW has to decide

when and by which initiated measure – usually a

manoeuvre to increase the expected passing distance

in due time – he can avoid a potential danger. This

decision making process should be supported by a

suitable collision warning, e.g. especially in multiple

encounters situations in areas with high traffic

density or when the OOW - by whatever reason -

has overseen such a developing situation. Finally,

the action has to be taken, its consequences have to

be controlled and, if necessary, to be corrected or

adjusted.

A detailed analysis of the investigation reports

dealing with collisions performed by the Nautical

Institute (Patraiko, 2008) showed that nearly 50% of

all collisions happened, because one of the involved

vessels had not recognised the other vessel.

3 INVESTIGATIONS AND

SELECTED RESULTS

A series of field studies was conducted on board of

ships to investigate the situation with respect to the

occurrence of alarms and their handling by the

bridge team. As the management and presentation of

alarms is influenced by the type of ship, the year of

construction, the installed equipment and grade of

integration, the sea area, the training and education

of the crew as well as by the safety standards of the

shipping company (Baldauf & Motz, 2006), these

factors were taken into account to obtain a profound

database.

The investigations aimed at several technical,

operational and human factors related aspects of the

situation onboard with respect to the alert occurrence

and handling. Within the context of this paper, the

focus is laid on results related to collisions warnings

triggered by and displayed at the ARPA-Radar

Human Machine Interface with integrated AIS

targets and superimposed by information of ECDIS

(Electronic Chart Display and Information System).

The timely distribution of alarms reflects the

dependence of the numbers of alarms from the sea

area. This hypothesis is further confirmed when

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analyzing the registered alarms in relation to the

navigational situation.

The field studies were carried out on board of six

vessels, which were two ferries operating in the

Baltic Sea, three container vessels (with container

capacities of 6.200 TEU, 5.500 TEU and 7.500

TEU) and a cruise vessel operating in the

Mediterranean Sea. All vessels were built or

reconstructed within the time span from 2001 until

2007. The ships’ bridges were equipped differently;

the equipment (among others AIS devices) was

integrated on a medium or high integration level.

The investigations were conducted during

voyages in the Baltic Sea, in the Western

Mediterranean Sea, in the North Sea and in the

English Channel. The average time of observation

was 19 hours, with a minimum of 11 hours and a

maximum of 27 hours. Even though the

investigations took place on different times of the

year, usually good weather conditions were

experienced with low winds and calm sea. During

one voyage temporary rain showers were

encountered during the night. Another vessel was

sailing through fog banks with restricted visibility up

to 200m for two hours of its voyage. Comprehensive

analysis of alarm recordings were performed and are

described in more detail by Motz, Baldauf and

Höckel (2008).

An important result of the analysed records was

that collision warnings form a major part of all types

of alarms registered during the studies. Figure 1

depicts the average percentage of the types of alarms

registered for the six vessels and highlights this

outcome. For all vessels investigated the majorities

of alarms are collision avoidance alarms together

with lost target alarms. Summed up they have a

portion of approximately 50%.

Waypoint alarms

Off track / Off course

12%

Chart data warning

Other

23%

Collision avoidance

alarms

30%

Lost target

20%

Figure 2: Average percentage for types of alarms for all

six vessels.

Additionally Figure 3 shows the average

percentages of the sources initiating collision war-

nings (CPA – (distance at) Closest Point of

Approach)/TCPA – Time to CPA) for all vessels

investigated. Both kinds of alarms were

predominantly caused by AIS information. This

percentage could have been even higher, if the

bridge team of one of the container vessel had not

chosen a radar setting without integration of AIS

information, which caused all CPA/TCPA and lost

target alarms to be initiated by radar information.

This result is to be expected because of the

technical configuration and the use of the automatic

alarm functions. For AIS, according to IMO

regulations, the same limit values have to be applied

as for tracked radar targets and the option for

CPA/TCPA calculation was switched on to sleeping

AIS targets by default. On the other hand a critical

fact is that 20% of all registered alarms are "Lost

target alarms", mainly caused by AIS. This is critical

as "Lost targets" are of minor importance compared

to safety-relevant collision warnings. Accordingly

their occurrence occupies the operator's attention

and workload capacity.

CPA/TCPA

Radar

28%

AIS

72%

Figure 3: Sources of collision warnings for all vessels of

the field studies.

Usual threshold configuration for CPA is from

0,5 to 1,0 nm and for TCPA from 12 to 15 min.

During the empirical studies it was observed that the

crew adapted the thresholds for CPA and TCPA

only very seldom. Moreover the navigating officers

often prefer to switch off the alarm by setting the

thresholds to zero. As investigated in former studies

(Baldauf, 1999) and confirmed by the results of

personal interviews based on structured

questionnaires, the navigators mentally use different

CPA limit values and adapt them especially

according to different types of situations (meeting on

opposite courses, overtaking or encounter on

crossing courses).

INVESTIGATIONS INTO ENHANCED ALERT MANAGEMENT FOR COLLISION AVOIDANCE IN SHIP-BORNE

INTEGRATED NAVIGATION SYSTEMS

171

4 APPROACH TO REDUCE THE

NUMBER OF COLLISION

WARNINGS

To guarantee the high safety standard in maritime

transport, as described above, there is a need to

reduce the number of alarms on board vessels. It is

necessary because the high frequency of occurring

alarms, obviously, do not contribute to a better

situation awareness of the watch keeping officers on

the ship's navigational bridge. Alarms should only

occur, if a real dangerous situation is developing and

the announcement confirms the mental risk

assessment of a well skilled and experienced

navigating officer.

This goal can be reached by combination and

pre-processing of available information to generate

and apply situation dependent thresholds for

example for the purposes of collision avoidance. In

this way, enhanced alert management of future

Integrated Navigation Systems (INS) will be able to

trigger more reliable collision warnings, but only in

that cases in which a navigator usually would have

to react.

For that specific purpose a first generic concept

is drafted. It is aimed to combine target information

from different sensors and manoeuvring information

that will be provided by Voyage Data Recorders

(VDR) and from ECDIS as well. A visualisation is

given in Figure 4.

Figure 4: Generic concept for combined use of

information provided by INS to self-adapting and

triggering situation dependent collision warnings

Presently, modern anti-collision-systems

triggering alarms, when the calculated passing

distance at the closest point of approach (CPA) and

the time to CPA (TCPA) are less then the limits

freely configured by the navigator.

Core element of the approach for reducing the

number of collision alarms is a risk model for

situation assessment. This model differs between

three types of encounter situations (head-on

encounter, overtaking and meeting on crossing

courses) and is considering the two conditions of

visibility as they are laid down in the International

Rules for Preventing Collisions at Sea (Cockcroft &

Lameijer, 2004). Furthermore the concept is applied

to the new IMO definition of alerts given in the new

performance standards for INS (IMO, 2007) and

allows for introducing situation dependent collision

alert categories "Caution", "Warning" and "Alarm"

as well. Cautions and warnings may be switched off

by the operator, but alarms may not.

For self adaptation of thresholds, different CPA

limits are foreseen, which will be set according to

the hydrodynamic safe passing distance related to

the dimensions of the involved ships, the actual sea

area as well as visibility conditions.

As suggestion for initial basic values CPA limits

were determined by a detailed field study. To ensure

a wide range of user acceptance one emphasis was

laid on the navigators' behaviour. From the point of

view of well experienced navigators it is rather more

practical to determine the safe passing distance with

respect to usual data. Under pragmatic aspects and

according to the investigations performed it can be

assumed that the nominal safe passing distance has

to be in relation to the ship's length of the largest

vessel L

max

involved in an encounter situation (L

max

should not be less than 1 cbl). Taking into account

different kinds of encounter situations as defined by

the COLREGs a factor "f

" is necessary which

depends on the kind of situation "x" (Safe Passing

Distance (nominal) = f

• L

max

Table 1: Recommendation for basic values to calculate

situation dependent threshold.

kind of encounter

situation

(good

visibility)

(restricted

visibility)

head-on situation

meeting port/port-side

2.5 5

Overtaking 2.5 5

head-on situation

meeting stb/stb

5 10

crossing situation 5 10

The values, given in the table above, are derived

from several investigations and are suggested for the

four main kinds of encounter situations. These

values were proved by simulation studies and are

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valid under the conditions "open sea" for good

(column 2) and restricted visibility (column 3).

The values derived here and used for this

approach are similar to values found by several other

studies (e.g. by Pietrzykowski & Uriasz (2009)) to

support safe manoeuvring in case of collision

avoidance.

On the other hand recorded manoeuvring data

will be used for automatic adaptation of the TCPA

related limits of the dangerous target alarms, either

by taking them directly from a database or by

calculations using fast time simulation algorithms

(Benedict et al, 2006). The response time for turning

manoeuvre is a fundamental value to avoid a

collision. Such response times are only available to

captains on board for some standard manoeuvres and

they are usually neither exactly known nor

applicable to the prevailing circumstances of a

concrete dangerous situation to be solved. A sample

of a standard set of response times for a normal

sized container vessel with a capacity of 5.000 TEUs

is given in the following table.

Table 2: Response times for turning manoeuvre depending

on own ships speed and rudder angles.

As stated before, when applying the drafted

concept for situation dependent alarm thresholds

those values maybe be determined from direct

recordings of the continuously working VDR. The

principal application's structure and the relevant data

flows are given in the figure below.

Again the values suggested here roughly

corresponds with values coming from ship domain

studies (Goodwin (1975)) but also with results

applying new concepts to determine critical distance

for manoeuvring according to the COLREGs (e.g.

Rymarz (2007).

Figure 5: Principal application structure and data flow for

self-adaptation of thresholds for collision alerts.

First studies applying the situation dependent

thresholds for detection of dangerous encounter

situations in overall traffic scenarios in sea areas off

the coast monitored by VTS leads to a reduction of

the number of collision alerts by 40%.

5 SUMMARY AND OUTLOOK

Investigations into ship borne Alert Management

were performed and are continuously ongoing to

improve the situation on board. Investigations into

the present situation on board have shown that there

is an urgent need for the reduction of the high

frequency of alerts. Presently collision alerts have a

major portion of all alerts occurring during normal

ship operation. That is why a concept for situation

dependent thresholds for collision alerts is

developed. The concept considers the situation

assessment of experienced navigating officers by

allowing different values according the type of

encounter situation and visibility conditions as well.

Combining available information and data from

different sensors of modern Integrated Navigation

Systems it is suggested to determine the situation

dependent thresholds taking into account the ship

dimensions of the involved ships and the

manoeuvring characteristics valid for the concrete

situation. First studies performed for purposes of

shore based detection of dangerous encounter

situations have shown that a significant reduction

(up to 40%) of the collision alerts frequency is

possible.

The investigations were part of projects funded

by the German Ministry of Transport, Building and

Urban Affairs and the German Ministry of

Education and Research. The results directly support

INVESTIGATIONS INTO ENHANCED ALERT MANAGEMENT FOR COLLISION AVOIDANCE IN SHIP-BORNE

INTEGRATED NAVIGATION SYSTEMS

173

the work of the International Maritime Organization

developing new performance standards for Bridge

Alert Management and contribute to the e-

Navigation concept.

The authors would like to thank the shipping

companies Peter Döhle, TT-Lines, Finnlines,

Scandlines, HAPAG-Lloyd and AIDA Cruises Ltd

for their grateful assistance and all mariners who

provided their knowledge in interviews on board.

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