Designing and testing a ship’s bridge layout

TE UUIVERSITT

Laboratorium voor Scheepshydromechanlca Archlef Mekolwog 2,2628 CD Deift Tel.: O15.78873.FacO15.781823

In: Ed. H. Kragt,En/i an cing Industrial Performwirc. EzperiencesofIntegrating the Hurnwi Factor, London -Washington DC, Taylor & Francis, 1992.

Designing aiid testing a ship's bridge layout

H. Schuffel

TNO Institute for Perception

Su ry

Trends towards reducing the costs of ship operation demand that the bridge be conceived as an operational centre for performing botti navigational and platform supervisory functions. Ori the one hand, a highly automated bridge supports efficient ship operation and makes single-handed performance possible. On the other hand, the need is emphasized for experimental testing of layout. mental workload and task performance with regard to safety. This chapter addresses some desigts issues, such as function allocation and the testing of perfornsance in a series of simulator experiments. After introducing the ship's hierarchical control process, and the process of allocating functions to be fultUied on the bridge, a notion on the ship handler's control behaviour for predicting effects of automation on performance is osinlined. Tise testing of a ship's bridge layout and a display tor path prediction by means ofsinnulator experiments. approximating real life conditions, is elaborated. Results show that careful function allocation can lead to an automated wheelhouse concept suitable for safe navigation in landfall conditions. Questions concerning the effects of monotonous svarch periods on operators alertness and ihe effects of the change in task structure on the operator's skill and ïntcrest n the job need further attention.

7. i

Introdiictioti

7.1.1 Scope

The search for more efficient ship operation has increased over the last decade. Shipping companies aim at reducing operational costs by extending automatic control, providing the opportunity to modify the ship's bridge into an operational centre from which both navigational and platform functions can be fulfilled,

such as planning and conducting sea-passages and supervising/monitoring status ofpropulsion, cargo and ship.

In a tiuniber of westcrn countries, projects have been undertaken to optimize design, operations, maintenance, investments and energy cotisumption against the criteria of costs, safety and efficiency. These projects follow the system approach of ergonomics. lu that approach the designer attempts to optimize

the system output for the criteria of safety, efficiency and well-being. He manages

this by balancing the interrelationships of the four main elements of the

man-ship system:

software (procedures, rules, regulations), hardware (displays, controls, process dynamics), environment (climate, vibrations, noise, lighting), and liveware (motivation, stress, skill).

From the ergonomics point of view, optimizingthe safety and efficiency of

ship control and the well-being of the personnel arc not primarily questions

of providing better equipment, but of integrating these fourelements to meet the criteria. The most critical exercise in this integration process is the function allocatïon; deciding which functions have to be performed by muco and which by automated equipment. When this had been decided, the layout of workstations

can be designed according to the results of the allocation process, and the

hypotheses on man-ship performance should be verified by means of simulation experimeilts.

In this chapter the function allocation process is outlined (section 7.1.2). lt

constitutes the basis for an automated wheelhouse concept for future merchant

vessels in The Netherlands. Further, a series of simulator experiments are described to show a verification of expected improvements on navigational

performance (sections 7.2 and 7.3). Finally, an analysis of IOU shipping accidents

is mentioned to estimate the effects of an automated wheelhouse concept on the safety of shipping (section 7.4).

7.1.2

Function allocation and design

Ship navigation is a hierarchically ordered process of comrol activities (Kelley, 1968); a planning, monitoring, and cxecutiiug level can be distinguished. At the highest level the master plans the passage. This is an infrequent activity, which mainly consists of decision making, based upon information of varying reliability

from different sources. At the intermediate level of control, tue mate is

monitoring deviations between the planned passage and the actual progress, and is supposed to anticipate the intended track and the ship's path by observation of surroundings and ship imuovements. The expected deviation between track

and path is minimized at the lowest level by heading and speed adjustments. At that level, the helmsman performs a compensating tracking task with the conupass as a display and the ship's wheel as a controller.

Historically, functions were allocated to equipment when engineers could produce a cost-effective replacement for a human operation. This led to the philosophy that those functions should be allocated to suitable equipment for

which the human operator has poor capabilities. The application of these rules reached its limits a number of years ago in cockpit design of aircraft, because

of a disharmony in the task structure. Wiener and Curry (1980) stated: '. autonuation is not a question of whether a fuiuctioiì can be automated, hut whether it should be due to various human factor issues.'. And 'It is highly

questionable whether total system is always enhanced by allocating functions

to automatic devices rather than human operators . .

Ship bridge layout design seems to have reached these limits too! In shipping,

automation has been fully applied to the lowest control level and partly to the other levels. Nautical and mechanical engineering officers are condemned io perform routine tasks for a large part of due watch period, and to detect and

diagnose failure for only brief periods ut time. Consequently, when .illocating

fuiuctions between personnel and machines, the designer needs to indicate effects

of low and high task load demands on the officers' behaviour and to provide

solutions to maintain safety standards. At low task load conditions, the offIcers' readiness to react and the maintaining of skills are critical issues, which can be compensated by both adding meaningful oilier tasks arid extensive simulator

trainiiig. High task load conditions iìight overload the operators in terms of

time, mental effort and stress. The present study is focused on high workload

conditions in coastal and congested areas. For these conditions, one of the

relevaiut questions is whether one ship handler (the Officer of the Watch) can cope with the mental workload, maintaining system performance at the actual average practice level.

The functions to be fulfilled on a bridge, conceived as ami operational centre, are navigation, commtinication, propulsion, course control, electricity supply and ship's condition monitoring. Concerning the allocation process. functions

were decomposed to such a detailed level that performance by personnel or

equipmeiit could be allocated unambiguously. Each decomposed fimiuction vas analysed (Scliutid et al., 1981) with regard to information source and information processing, control criteria and actions, statistics of accidents (Drager, l98) amid human factors data (Salvendy, 1987).

As shown in Table 7.1, the results of the allocation emphasized the Officer of the Watch's role as a look-out, decision maker and supervisor of autonuatons. whereas control functions are limited to set-point adjustment. At the planning level the officer eau be assisted by computers for optimizing due route with regard to mnininial fuel usage, but decisioii support systems are noi yet applicable and have to await further development. At the iiiternucdiare level the computer can support monitoring functions. For instance, the Automiìatcd Radar Plotting Aid

(ARPA) is superior in detecting and tracking targets on the radar display. However, the identification of targets needs the human eye. At the control level the adaptive autopilot can replace the lielnìsmaiu.

I,î/I« - / ,'ilIHIilI} t) i /iIticfl&i :IL(n?, J)IO(eSS /r IumIm iio,-khjil o;,Iit,o,:s u

The expansion of automatically controlled functions and the availability of

electro-optical computer-controlled displays make the design of workst.itions tor single-handed operation Ii.isiblc. In Figure 7. 1 the iimock-up ofa future bridge

l.sigii cOncept is shown.

mrea.s.. 1, it,r'usiteI flftttfit)ll .!, HIlHUiI /iI,it,)l,5

Activities Perceptioiì Functions

lu furnì ation processing rvlotor conun)I Pl.mnniiig A M A M M tVloimitoriiim. A M A M Exccu tri mg A A A

liç'tise 7. I ¡zci:ire Ithe ??It)k-Idp of ijutiire I1rjle I1y1ut u'ith a Seth -Iluotnahie (JtIF(

tihI i,ii LI:spIa)'s JETE ?hI&)l??(OiIJ!1 ?htt'U.,'alU),I liti! (ILUIHI H

In Figure 7.2 a sketch ot the navigation display is presented. The threelevels

ot information concerning planning, monitoring and executing activities are

presented in different colours to enhance ovcrvicw and detailed information at

one glance (Baty and Watkins, 1979). The

planning information contains

geographical. wave, wind and intended track data. The monitoring information

SPEED REVS

Ii'miit' 7.2 .'\,iI'Siitli'Ii !isjtla1 utili iituii'iiitetIIIIIE)Ihlilttillil íillliiiiIIiiÇ' ¡IhiuI,Ii?I1l, i?utlhuutiIiilii_,I titi!

I.\II IITfltt liiII/tl II!i (Illil, IiISI 01 lll!0Ii?Iiit0lI ilii.!Ilt (0 Ii /'li, lift Ill lil/eutu

liu.

consists of the ship's position and movement status, such as heading, change

of heading, under keel clearance and its change, a ground related velocity vector and echoes of ships, with velocity vectors calculated by the ARPA automaton. Information at the lowest level shows the rudder deflection and shaft revolutions

stat u s.

7.1.3

Ship handler's control behaviour

In order to postulate hypotheses on the interaction ofbndge layout with human

control behaviour, the notion is introducedthat the ship handler's activities in controlling a ship in narrow or inland fairways is niainly based on feedback and to a minor extent on preprogrammed control (Schuffel, 1986). Feedback

is effective for accurate control when references for correctness of performance

(perceptual memory) have been developed (see Figure 7.3). The perceptual memory contains the relationship between desired outcome, past and actual

system outcomes and expected ship movements in the environment asperceived

by the ship handler. In tracking tasks withrelatively ample time and space for correcting control actions, perceptual memoryis dominant. The ship handler

carries out inaccurate motor memory-based rudder deflections. After watching the resulting ship's movements, the expected ship movements are compared with

the actual movements. The role of the motor memory is to produce small adjustive movements which are subsequently controlled by the perceptual

memory through comnparmg expected and actual outcomes. In earlypractice, learning depends fully on knowledge of results (KR), because this provides the only means through which the subjects are informed about deviations between intended track and travelled path. With practice the perceptual memory is built

up and the need for KR

decreases. KR is conceived as externally provided

information about the ultimately realized and desired outcome, and is

distin-guished from feedback generated during performance by system responses in

the environment (Schmidt, 1982). 20-ISO '5 loo ta- ₈₆ post r udder dei t cc t tons mo or memory -1 r udder del tectiori spec iticatiofl

Iititii - I fuis liiii,i llItsti,tH. ¡luit

I S] ((((Oil, fl /ii5/Jii J/I( j(,il(H'

ii

,i/

124 Workplace design (inicio) S/mips brid,ge ¡ayote lesi'ut 125

!I)

50

0- O

2iO 3i10 3k 310 3i0

60 ROT 80 80 ¿0 30 20 10 0 lO 20 30 ¿0 50 ni t tot co nd it tons desired outcome

posi and percep - POSI

actual tuoi ship

outcomes memory movements

i

ex p ecl ed

ship

move me r,t s

jiililti !i/jeiftiitt 0!itt!tìtttt0lt0 titi! 5/ijj) iiitt'u(tt'hIi j(,II iii,IH,',( iii Iiit(i,(l ,iilili(filii' liii!ihyirt'iI ,ii(uiie.

In tracking tasks with little tinìe and space for corrective control actions,

preprograrmiling of control actions becomes more important. However, em-pirica! evidence indicates that the specification of rudder detlections as a function

of minal conditions and desired outcome (ship's desired future position or orientation) is inadequate (Schuffel. 1986). The travelled path will, therefore, deviate from the intended track. From this theoretical notion, two hypotheses

are inferred with regard to the previously mentioned automatic equipment for

the conduct of vessels.

In section 7.2, the hypothesis is tested whether feedback control is enhanced by clear presentation of references for correctness of performance. Supporting

feedback control will decrease mental workload and allows the addition of platform monitoring functions to the navigation function.

In section 7.3, the hypothesis is tested whether preprogrammed control is improved by automatic path prediction. Supporting preprogrammed control

might enhance manoeuvring accuracy in congested arcas, which is particularly

relevant where time and space for correcting control actions are lacking. The possible impact of supporting feedback control and preprogrammed

control on the safety of shipping by means oían automated wheelhouse concept

is estimated in section 7.4.

7.2

Mental workload

7.2.1

Method

The addition of platform monitoring functions to the navigation function refers to the question of whether one ship handler can cope with the mental workload.

The tasks to be performed by the operator to fulfil these functions impose a

mental load on the operator. Mennil load is defined here as the degree to which a task appeals to active processing ofinformation, that is, the number of conscious

cognitive operations per unit of time.

The mental load of a primary task can be measured by using a standardized

second task that requires continuous active information processing. The

procedure is as follows: after trainiiig, the performance on the second task is

measured separately; next, the second task has to be executed while navigating. The resulting performance reduction on the second task reflects the mental load

of the navigation task.

To investigate the effects of automatic equipment on the mental workload of the Officer of the Watch and on the accuracy of navigation, performance

of single-handed operation in an automated ship's bridge, the so-called 'Bridge '90' lias been tested against ari average conventional bridge with two- and

one-person control (Boer and Schuffel, l985a,b; Boer et al., 1986).

The mental load of the navigation task is expected to be larger in the

one-officer-operated conventional bridge compared to a two-one-officer-operated con-ventional bridge and a one-officer-operated automated bridge. The main reason is that the design

of

Bridge '90 has been aimed at technical nitomatit in of routine

tasks (e.g. position estiniation) and optinuzing information presentation by

integrating relevant parameters on a navigation manoeuvring display (see Figure

7.2). Hence, as much attention as possible is free for planning and decision

making as well as for a proper execution

of

additional tasks. In the conventional bridge, two officers are considered by maritime authorities to be quite capable ofexecuting navigation and additional tasks. For one officer, however, it is

believed that too much time is lost by sampling necessary information and too

much attention is consumed by routine tasks to allow a proper execution of

additional tasks.

In three simulator experiments, a total of32 representative watch officers had

to follow predetermined tracks in a coastal area with a 40 000 ton container vessel. The visibility range was 5 km, there was moderate traffic density and

normal current and wind conditions. Deviations from the predetermined track

were calculated as root mean squared error to indicate accuracy ofcontrol. A

continous aurally-presented memory task (CMT) was used to determine the

mental workload that the navigation task imposed on the Officer of the Watch. Subjects were asked to memorize four consonants in randomly presented letters

of alphabet during 7 min. The sum of the absolute number of deviations as a

percentage of the total number of target consonants was calculated to indicate

workload. Three main conditions were investigated:

A conventional bridge with an Officer of the Watch charged with conning functions, assisted by a tracking officer (condition A).

A conventional bridge with single-handed vvatch (condition 13). Bridge '9() with single-handed watch (condition C).

7.2.2 Results

Navigation accuracy

In Figure 7.4, percentages of the time (averaged over tracks and subjects) that the ship travelled within intervals of 100 m from the intended track are given for the three conditions. In Table 7.2, the results oft-tests are presented. From

Figure 7.4 and Table 7.2 it becomes clear that navigation accuracy differs

significantly among the three conditions. Navigation performance is superior in Bridge '90. Path width remains within 400 ¡n for 95o/ of the time. In contrast, two-officer operation iii the conventional bridge results in a comparable path

width of 800 m, and one-officer operation even in 1200 ni.

.íeuta! load

In Figure 7.5, mean error percentages of the CMT of the control and

experimental conditions are presented. Table 7.3 contains the results of a non-parametric statistical analysis of the results. No significant differences can he found between the mental load of the navigation task mn the two-officer-operated conventional bridge as compared to Bridge '90. Perhaps even more surprising is tlì.it fur these coiiditioiis (A lun C). only a slight. nid not sigmiiticaiit. nlc'ijtiOii

14'orkplaí'e desi,, (micro) 60 E Condition A B 100 80 20 o

distance tram track 1ml

I:j,t,t.t.7.4 ,Îea,, percentages oft/u' trate/lcd tigne 1/tat tite s/tip remained u'ithin interi'aIs tf 100 n: haul 1/Il'track.B '90 (¡p), Brjtlt,'e' '91) n'lt/I sin1e-ha,ulej watch cant B (2p) co,l:entiona! ltrid'e

flit/I n, oc'r f the wale/i 1z,td a tntcki,i i.[ficer cotti'B (¡p), cotu'l'utnttIIl bridge tOit!:

siti'/c-Il,Illhii Hat/I. UD( 8n1Qi: 8" 8 0890 IlpI cona812p1 lUll cocaBlipi

InvestIgated condItions

Ftl'llrl' 7.5 _{Coutltlllolis nemory task error perceutaes in till' iontwi} Ilid i?lI','5tii'I(,'j

.S,'e I'tt,'llrl' 7,4/or ,,leag,in _{f key.}

r,hI 2 _{Results of t-tests nl jIlt/I l'uit!: lhflerences lnlI'tu' till' t/lfl'l' i)lllhtic,tts: A, 101u'l'ittt011ltl}

ilt'lIll,'l' Illt/I tIlo officers; H ottl'etltu'nt/ I'TilIl,'l' tl'it/t l'lll' o/fict't; C, Bl'ilI'e '90 uit!: ilttC officer

¡1< Ol P°zUOl

-

P<0,Ol

S/tip 's bridge layout des(n 129

Tabh'7.3 Results of tlon-parametric slltlStlÛll tests for till' (OtltllIl1011S ltu'tlloty 105k peltntlall(e Ill till' ¡lll'l'StII,',lIl'il (OlIdIt101tS (lIs., 111)1 Slcllt/Iñlllt)

('otldItlilI Control A B C

Control - u.s. P<OOl u.s.

A - - P<OOl u.s.

B - .- - P<OOl

C

from the control condition can be observed, This reflects that the mental load of the navigation task is quite low. In contrast, the mental load of the navigation task in the one-officer-operated conventional bridge (B) is significantly higher

as compared to the control, A and C condition. This difference suggests the presence of attention-demanding task components (notably position estimation). 7.2.3 Discussion

7.3

Pat/i prediction

7.3.1

Method

Enhancing human control of slow responding systems by means of prediction is vcll known (e.g. Bernotat and Widlok, 1965; Kelley, 1976). Applications of path prediction in the maritime field, however, arc hardly available, presumably ftr reasons of inadequate quality of predictions and deficiencies in proving oper-.ltmoIial advantages. The predictor presented here (Passenier, 1988) uses as inputs

ship's position .1:1(1 lfcading. and provides for a selected rudder deflection the

Observed differences in navigation performance and mental load of the

navigation task can directly be attributed to bridge design on the one hand and the number of officers on the other hand. As mentioned before, the two-officer-operated conventional bridge served as standard against which other conditions were tested. As far as Bridge '90 is concerned, it may be observed that due to accurately and continuously presented position feedback, navigation performance is superior as compared to the other conditions. As a consequence, navigation

accuracy is improved.

The more accurate navigation in Bridge '90 does not seem to increase the

mental load ofthe navigation task (Table 7.3 comparison A vs. C). Apparently, the greater frequency at which actual position is monitored, as well as decisions ou control actions resulting from these observations, hardly require attention.

This conclusion is supported by the fict that CMT error percentage in Bridge '90 does not differ from the error percentage in the control condition.

lii this section, the feedback control element ofhuman control behaviour and

its support was elaborated. The text section will focus attention on the

)lldIllill5. preprogrammed control clement.

A B C contrat B YO lip) cony B 12p) I'll" cony B 'lp) 60 30 20-o Ql

r

130 Workplace desq:i (micro)

ship's future path. A special feature is the self-tuning characteristic for

compen-sating disturbances due to wind, waves and water depth.

For testing thc effectiveness of this path predictor, a simulator experiment

was conducted in which the need for preprogrammed control actions was varied by means of the magnitude of course changes (Van Breda and Schuffel, 1988). Twelve representative subjects, Officers of the Watch in active service, controlled

three times a 40 000 ton container vessel along six predetermined tracks,

containing five course changes (15. 30, 45, 75, 105°) in random sequence. The

intended track was shown on the navigation display, depicting also the ship's heading, turn rate, speed and rudder def'ection. l)eviations 1mm the intended track were calculated as root mean squared error.

Three main conditions were investigated:

path prediction (PP), showing the ship's future path,

ground velocity vector (GV), showing the ship's movements and position relative to the sea-bottom and the intended track,

parallel indexing (Pl), showing the intended track.

With PP, the Officer of the Watch is pursuing the intended track. The predicted

path is a continuously visible curve changing with trial (rudder) input. The Officer of the Watch can fully anticipate the ship's path. In combination with

the presented intended track, this provides an adequate way for muimmizing future

error (see Figure 7.6).

heading 60 60 40 330 rate 37de9/min 270 NORTH UP RELATIVE MODE RklCflflLn 300 60

-,

.., , 40 60 80 30 speed tOs) 240 i ₁₂₀ 210 ¶50 rudder dey) p Jfl (lID Q 1í 70 30 B R

Fitp,re 7.6 Pat/i predictwti, depicted by solid lint, nit/i actual he,di,p,,' (40°;Jmne lotted line) nil

¡ntet,detl track (das/ud line) partly parallelnit,' predicted pat/i (sie also Fiuru' 7.2).

With GV (Pew, 1966), the Officer of the Watch can anticipate the ship's movements by extrapolation of the velocity vector. In conabination with the

presented track, diere is a moderate condition for niinimiziiìt future error (see

Figure 7,7, heading , , 80 60 rate 37deg/min 270 300 260 NORTH UP RELATIVE MODE RANGE 20 NM r udder dey) p iíi

Ship 's hridi,'e it yolli desitti 13 1

40 330 210 40 B) 80 30 60 120 speed lits) 90 15 10

Fi,tre 7. 7 Gniitt,d velocity vector, depicted b y a solitI lit,,' WI t?! actual headin, (40°; fitte lotted li, e) and in tended track (das/led line) (set' 01511 Fi'ure 7.2).

With PI, principally the intended track is pursued. Compass and turn-rate

indicator provide nsinimal means to anticipate ship's movement and future errors

between track and path (see Figure 7.8).

7.3.2 Results

lu Figure 7.9, the deviation from the iiìtcnded track, calculated as the route nican squared error is shown. The path prediction condition shows significant accurate

Fit,'ii,'e ThS' Pata/II iiIlexItIi, /r i'.vjieritt:t'titil pIItp(se2 sntiphhui'd ro a pursuit ttutkiut,' task UIl/I

i 11111 //ui(' 14(1 ¡hit' littid ¡titi attI i,iletilel riak' (i/il/leI ltne (sie i/so l-i'uie 7.2)

'i 240 i

___

NORTH UP RELATIVE MODE RANGE 20 NM B DEG R NM rudder

dey) p _io ' 20 jIlt

íbt'

'o i'i 's

'5 10 DEG NM 20 20 B R DEG NM

performance (F = 65 '6; df 2,22; P< 0.01). The inaccuracy of manocuvring with the GV and the PI method particularly occurs at large course changes as was expected. Under these conditions, the control behaviour is supported effectively by prediction.

7.3.3 Discussion

The results show improved control accuracy when using PP. Especially when performing track keeping tasks with large course changes, there is a reduction in deviation from the intended route of about 70%. PP supports preprogrammed control which appears to be most effective at large course changes. However, results (Figure 7.9) suggest that a path predictor is even more effective than the

use of a ground vector or a reference track at small course changes.

In the following section, the possible impact of supporting control behaviour

on the safety of shipping is estimated.

200 loo -

.PI

GV 0 PP

:7

in an activity-fuiìction matrix. In this exploratory study, three experts (an

ergonomist, a nautical officer and a psychologist) estimated on the base of fault-tree analysis, whether the automated wheelhouse concept would haveaffected the occurrence of the events. lt was expected that differences between the number

of

events related to accidents with conventional ship bridges and to supposed

accidents with the advanced automated bridge, would reveal advantages and disadvantages of the function allocation process and the inferred automated

wheelhouse concept. 7.4.2 Results

The results showed that 276 events were involved in the 100 shipping accidents. This number of events consisted of 209 events related to human errors, 24 related to hardware errors. 9 related to procedural errors and 34 related to environmental errors. The automated wheelhouse concept would have reduced the amountof

276 events to 88; a reduction

of

68%!

Regarding the reduction of the number of events related to human error only,

Table 7.4 provides an overview. The 209 human error-related events were reduced by the automated bridge with the number of 162 to a remuant of 47

events.

7.4.3 Discussion

The results showed that the automated wheelhouse concept night be highly effective to reduce human errors. Hardware and procedural errors might be

affected to a lesser degree. Environmental factors, including communication amid information exchange between ship and shore seem to be hardly affected. This

emphasized that the effectiveness of the automated wheelhouse concept is, of course, also dependent on the organization of the shipping company and the

ullaritime authority.

The djstrjl)uti(,n of the events over activities and functions shows that iii p.irtieulir errors could be prevented in the performance of the information

Til'it' 7.4 Riilin 110,, 0/1/ic ,i,i,,i/ir o/hin,,,,, error-re/arid ii'i'iit cO?iCtpl

liii, io fi,, aiiioinaied I'IieeihouIt'

Ac tiviti i: s Perception Information

processing

Functions inforniation

storage

t landliiig Rest Total

Vovj,.c ph.uiiiing 27 2 O O 30

Voac execution 19 65 4 O O 88

(1)nuhlli ii lcauon 4 o o O 6

Monuirnig tasks 0 28 9 O 38

Total J.) ₂₄ IS O I 162

I 32 t t'oikplace desit'n (iiiicro) Sii ip /rsdge la >'oi it li,sii,,, I 33

15 30 ¿.5 75 105

course change I

Fimire 7.9 7/ic dejiano,, /'e!iiic?i ¡in k nid pii/i o i fnuli,i f ii/irmiiltIoIt prescim(itsoii nid

cours,' cIm1n'e, ii'criii'd oler siui;jeco nid ieplieiiuio. l'i, pani/lei iiide.vniçp C I , i,'ri'u,,,d veloci!>' 't'eroi; ¡)J), juli predi 1,0,,.

7.4

Possible reduction f shipping accidents

7.4.1

Method

The causes of 100 Netherlands shipping accidents (1982-5) vere analysed vidi regard to the i.jucstioii whether an automated wheelhouse concept could have prevented these accidents (Schulfcl. 1987). Events necessarily coiiirihiititrs ti)

processing functions. With regard to the simulator experiment _{results, these}

improvements are interpreted as the improvements of navigational performance supported by the semi-automatic chart table, the integrated ARPA-manoeuvring display and the availability of navigational and auxiliary systems information

at one position (see also section 7.1.2).

7.5

C'onclusions and Recoin inendatio,

is

In the first place, it has to be emphasized that tue_{investigations concerned a} feasibility study, primarily concentrated on human performance. The results

support the idea that supervisory control in landfall condition is feasible in_terms of navigational performance and mental workload of the Officer of the Watch. In the second place, however, it is obvious that a number of other important

items have not been addressed. On the one hand, the effects of_monotonous watch conditions on the operators' alertness and the effects of the change in the task structurefrom active manual control_{to passive monitoring activities}

on the operators' skill and interest in the job, need

_{more research. On the}

other hand, the progress of technological development and the reliability uf automatons and human beings is assumed on the basis _{ofsimilar developments}

in aviation. Although the suggested technology is not extremely advanced,

applications of clectro-optical computer-controlled displays and the related chain

of sensors, as well as data preprocessing and data transmission is not widely

spread in the maritime field. Currently undertaken projects, such as the

develop-merit of the electronic chart, indicate that progress may be expected here.

7.6

Evaluation

It is speculated that the annual number of_{accidents will decrease dramatically} when the automated bridge concept is put into practice. The costs of studies and the investments due to new equipment are negligible (presumably I % of the design costs), in comparison with the_{estimated prevention of injury, loss} of life and the saving of environment and _capital.

A second weighing concerns the interpretation of experimental results. As shown, the idea of 'back-to-back' experimentation _{was used in a trackiiig task} paradigm (Gopher and Sanders, 1984). Results from simulator experiments,

approximating real-life conditions, \vere combined with laboratory experiments, based on theoretical considerations. Particularly, the theoretical notions and the laboratory experinients enabled the prediction and interpretation of the effects

of system elements on performance. The

_{converging evidence from both}

approaches bridged the gap between the _{more theoretical experiments and the}

realism of the simulator, allowing generalization and the specific application of

the experimental findings.

References

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