submission - Independent Pilots Association

,1989 )argr.res that. up to 24 hou¡s without slecp, crrcad¡an influenc¡s probabl¡ have greater
cÌTects tha¡¡ time since awake.
ln Japan. 8J..1 percent of d¡o*siness-related near accidens in elect¡ic motor locomotive dnr6¡5
rKogi & Ohtå" 1975) occur at night. Othcr landma¡k srudies ovcr the past scveral decadcs
bave docunæntcd the increasc in accidcns and crror making. Klein et al. (1970) argue that thei¡
resca¡ch uitlr simulators proyes that night flighs are a gr€åtcr risk ùan day fìights. Thei¡ rcscarch
fot¡nd 75- to 100-pcrccnt rrìcan perforrnancc efticicncy dccrcments i¡ simulator flighs during the
carly rnoruing bours, rcgardless of extcroal fætor s¡ch as darkncss or increasing night tra-ff¡c or
possible *'e¿ther conditions.
Task perforrnâncc in a varicry of nigbtiù6 has bcen comparcd with pcrformancc of tbcir dayrtnrc
co.¡nrcrparts. and rcsults consisæntly show dc¡erior¿ion of pcrfonnance on the night shift.
Browne ( 1949) srudied tclephonc opcraor:s' responsc tirnc in answering incoming callc in relation
ro rhe bour of the day and found tbc lmges nesponsc ti¡rrcs occr¡rred bctwccn 0300 and 0400
bours. Bjcrær et al. (1955) exami¡cd t¡ìs company hourly ledger computations of gas produccd
and gas uscd over an l8-year perid and found that rccording error werc highest at 0300 hor¡rs
rirh a smallcr sccondary pcak at l50O bot¡rs. Hildcbrandt et d. (1971). investigating automatic
u:ain braking and acoustical warni¡g signal alarrns sct-ofrs, also for,¡¡d rwo peaks u 0300 and
1500 hor¡rs in thesc safery-rclatcd eveots. Simila¡ ñnding have been rcported in ur¡ck accidcnts
fHa¡ris, 197'l¡ and in Ai¡ Forcc aircrañ æcidcnts (Rjbak et al., l9t3). Othcr accident analyscs of
unrc of day and hours of work show ¡hat borh ci¡cadian rhyttun and hor.¡¡s of dury play a
srgnificant role in the occurrence of accidents (Folka¡d, 1997:l¡n¡c et al., 1997). tn addition. the
incidence of accrdental injury nearly doubles dunng tàe night shrft compared to morning shjfr.
rrhrle tlrc rveriry of injr.ry i¡creascs 23 pcrccnt (Sm¡th et al., 1994). Night nurses make nearly
r*ice the pauent medication errors as da)'nurses and expcrience nearlv tlr¡e¿ tinrcs the auto
ac,-idents corrmutine to and from *'ork (Gold et al.. 1993).
\Ìerstedr rl988l revie*'ed the effecs of slecpiness from ni_eht shift *ork and found rhat the
¡.'tentiaJl¡ hazardous siruatron resulting from i¡creascd sleepiness dunng night shrft is reaj and
underesrrmared. Akerstedt (19t8) also rcports that fatigue rn shrft *orkers is highcr rhan in dav
*orkers. h.rghesr in night workers, folloned by morning workers Over¿ll, sleepiness among rught
norken s estrmaled to be around t0 to 90 percent. Rotì et al. (1991) i¡dicaæ that rates for
'¡orkers ialling aslecp on tle job whrJe on night shift have bcen reported to be as high as 20
Pcrce nt.
\ight operations are physiolopcally different than day operaùons due to ci¡cadlan trough and
sleep loss. This cames a higber pbysiologrcal cost and imposes greater nsks of accidents. One of
ûre most established safety issues is working in the circadian trougb be rueen 0200 and 0600.
During this period workers experience considerable sleepiness, slouer responsc times, i¡cre¿scd
errors and accidens (Mitler, l99l:Pack, 1994). Nlany recent accidenr from various
ransponåtion modes hare been ass,rciated *'ith tlus cúcadian trough (Lauber & Ka¡ten, 1988).
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