This study was based on data collected by the safety and health services during the past 38 years covering 668 accidents (First 10 years were 3 shift backward rotation, last 28 years were 4.4.4. with 48 hour breaks following each shift block. All are three shift rotation.

The following factors were considered:  The effects of the time of day, time on task, part of the shift block, day of the week and season of the year.

The injury risk did not seem to be higher on the night shift in terms of frequency,  but more severe accidents occured on the night than on day shifts.  More injuries were observed at the end of the shift, at the 2nd part of the shift block, and in the summer.  The accident rate was lower at weekend, especially on Sundays.

It has been found that the night shift was not as dangerous as it might have been presumed, taking into account the lowered level of human performance and accumulation of fatigue.

The sharp rise of the accident rate in the second hour of the morning shift was observed, and it could be assumed that it reflected both the organizational factor; the presence of more workers and management personnel at this time of day, and the fatigue effect due to the early beginning of the shift at 6 a.m.

We assume that delaying the shift's beginning to 7 - 7:30 a.m., could result in diminishing the worker morning fatigue and improving their well being as well as alertness and vigilance.

In both working situations, and in spite of their own specialties, the results illustrate the importance of cooperative activity.

Why do nurses plan cooperative tasks in the middle of the night? Why do the controllers consult more information relative to the other parts of the facility in the afternoon? We think this could prove the existence of activities which are interdependent and inter-individual in order to cope with the personal alertness fluctuations. In both situations, working together avoids isolation, work monotony and decreased vigilance.

The results indicate that even when workers have a specialization, voluntary cooperative efforts result in reduced isolation and increased vigilance. Workers defend cooperative work against the present tendency to reduce teamwork, especially at night, to a single person.

 What could be done at our place of work to increase vigilance and safety through teamwork on the night shift?

Research porvided by: P.K. Nag.V.G Patel National Institute of Occupational Health, Indian Council of Medical Research,This  Ahmedabad 380016, India. Oct. 1995 International Journal of Industrial Ergonomics Vol 21, Nos. 3-4, 275-281

This study examined the risk potentials and accident patterns among the monthly rotating shiftworkers and permanent nightworkers in textile industries in India.

At the beginning of the work shift, the production process raises possibilities for risks of accidents. This is particularly true in the case of morning shift.  For example, after three hours of work there is demand of speedy work.  This is considered a dangerous period and accident rate touches peak at the fourth hour of the shift.
Beyond the fifth or sixth hour, however, human fatigue is probably responsible for further risk of accidents. Compared to the morning shift, however, the rate of accidents is relatively less on the afternoon shift, with no major difference between the first and second half of the shift.  Despite that, the number of accidents on night shift is less than on other shifts, but there is a consistent rise in the percentage of accidents reaching a peak at fifth or sixth hour of work.

In general, higher percentage of accidents in the later part of the nightshift may be attributed to performance decrement, fatigue and lack of arousal associated with disturbed circadian rhythms.

Summary
The results indicated that more accidents happened on first shift between three and four hours of work. Afternoon shift did not have many accidents. third shift had the least of all.  However, on third there was a peak in accidents at the 5th and 6th hour of work.  It was reported that the main problems in accidents are concerned with the lack of organizational commitment and decision making in the issues related to occupational health and safety.

Research provided by: Ian Macdonald, Lawrence Smith, Sarah L. Lowe, Simon Folkard. U.K. 1997

This study aimed to determine whether there was a peak in accidents in the second to fourth hours within a shift and to compare the effects on accidents of the presence or absence of a break of only eight hours between shifts in a shift cycle ("quick returns") Archival accident records were obtained for a four-year period from two sister works within the same division of a heavy-industrial organization. The works had many similarities but differed in the shift systems uses. One had "quick returns" whereas the other did not. Accident frequencies were analyzed across four variables, site, shift, time on shift, and process code (process code identified the process area in which the worker operated.)

The results indicated there was a peak in accidents in the second and third hours into a shift, but provided only slight evidence for a detrimental effect of "quick returns."  

Reseasrch provided by:Carlla S. Smith, Gary S. Silberman, Teresa M. Heckert, Michelle H. Brodke, Bob E. Hayes, Marian K. Solverman, Laura K. Mattimore. USA 1997

To assess specific shift-related differences injury events and resulting injuries in a fixed-shift (plastics) plant and rotating–shift (glass) plant. To circumvent the analytical problems associated with industrial injury measurement, they used an expanded database consisting of injury self-reports (near-miss events and reported and unreported events and resulting injuries) in addition to recorded injury data.

The results indicated shift differences in both the numbers and the types of injury events and resulting injuries in the glass plant. In both plants, the self-report data yielded information beyond the recorded injury data. The authors believe that these expanded injury data can provide a useful safety-assessment too.

Details: The plastics plant had higher instances of "slipped or tripped," "hit by equipment or object," "got caught in or hit part of body on equipment or object," "moved equipment or object incorrectly or that was too heavy," or "used tools incorrectly". Workers on shift 1 reported the greatest frequency for each injury event. Workers on shifts 2 and 3 reported that they "used tools incorrectly" more frequently than did workers on shift 1

Rotating workers (glass plant) indicated injury events and resulting injuries both differed (equally) across shifts. However no individual injury event or injury was significant except the injury "broken bones" which occurred three times on the first shift versus none on the other shifts.

1) Workers who voluntarily help each other have increased vigilance on the job.

2) It is better, for safety reasons, to have only one person at a work station at a time on the night shift.

3)  Most accidents happen at the end of the first shift.

4)  Night shift has the most accidents.

5) On the third (midnight) shift, there is a peak of accidents at 3 and 4 hours into the shift.

6) A quick turn-around, (8 hours off) does not have a detrimental effect in terms of safety.

7) Accidents and injuries on all shifts are just about the same.

8) Good company records should give you the accident/injury information you need.

9) Very tired shiftworkers could have the same performance impairments as certain levels of blood alcohol concentrations.

Research provided by: From Preemployment Personality Testing for Loss Control. By John Amp, Ph.D., The St. Paul Companies. MC-505E. Printed in Professional Safety. American Society of Safety Engineers. June 1991, page 38.

 In one study, on-the-job accident histories of 157 construction workers were compared to those workers' scores on the California Psychological Inventory, a popular general-purpose personality test. Higher accident rates were found for workers with lower scores on scales titled Responsibility, Self Control, Socialization, Conformance, Good Impression, Well Being, Social Presence, and Flexibility. This pattern of scores characterizing workers with accidents could be summarized as an antisocial (rebellious) personality.

According to Hansen ( a researcher cited in Professional Safety, June 1991), people with higher accidents rates tend to be more impulsive, rebellious, hostile, and neurotic, and to have an external locus of control.

* (External locus of control indicates a belief that there are other factors beyond your control that are responsible for outcomes, including accidents. Internal locus of control reflects the belief that, in general, you are responsible for your own actions, including accidents. )