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Studies of accidents leading to minor injuries in the U.K. coal mining industry∗
Journal of Occupational Accidents, 2 (1980) 305-323 o Elsevier Scientific Publishing Company, Amsterdam
305 -
Printed
in Belgium.
STUDIES OF ACCIDENTS LEADING TO MINOR INJURIES IN THE U.K. COAL MINING INDUSTRY *
CLIVE
Safety Safety
NUSSEY
Engineering Laboratory, Research and Laboratory Executive, Red Hill, Sheffield S3 7HQ (U.K.)
(Received
November
13, 1979;
accepted
21 November
Services Division,
Health and
1979)
ABSTRACT Nussey, C., 1980. Studies of accidents leading to minor injuries industry. Journal of Occupational Accidents, 2: 305-323.
in the U.K. coal mining
The Safety Engineering Laboratory (SEL) (part of the former Safety in Mines Research Establishment, SMRE) of the Health and Safety Executive (HSE) has recently participated in two field studies of accidents among British coal miners. The studies have been carried out in cooperation with the National Coal Board (NCB) and have concentrated on accidents leading to relatively minor injuries, i.e. those involving absences for more than three working days (some 50,000 each year) and less severe injuries. The paper describes and discusses the methods employed (including the use of a questionnaire machine) to collect fairly detailed information directly from individuals who had suffered minor injuries, with a view to identifying causative factors; outlines some of the techniques that have been used to analyse the data; and reviews some of the findings.
1. IMPORTANCE
OF MINOR
INJURIES
The report on Health and Safety in Mines and Quarries for 1975 (Health and Safety Executive, 1976a) shows that, between the years 1972 and 1975, 256 men were killed and 2155 suffered “serious bodily” injury in British coal mines. Such severe injuries are reportable to the Inspectorate of Mines and Quarries. Over the same period, the report shows that there were 228,099 less severe injuries for which men were absent from work for more than three days (over-3-day injuries). Other work (Tregelles and Senneck, 1973; Proctor. 1974) suggests that injuries requiring treatment at colliery medical centres are about five times as frequent as over-3-day injuries. In terms of numbers alone these “minor” injuries (including over-3-day) are a significant problem in the mining industry; indeed apart from the aggregate pain and suffering involved they represent a considerable proportion of the *Based on a paper presented at the Seminar on Occupational Accident Research, Haikko, Finland, 13-17 November 1978. (Proceedings to be published by the Institute of Occupational Health, Finland.)
306
direct cost to the National Coal Board (NCB) of all accidents (Robens, 1972; Tregelles and Senneck, 1973). Because of the large numbers of minor injuries, it is probable that studies of the circumstances in which they occur will highlight some common problems, and some that are different from those leading to serious injuries. Insight into this latter aspect of minor injury causation can be derived from a study of the numbers (or proportions) of different types of accident at different severity levels. Such figures, derived from the report on Health and Safety in Mines and Quarries 1975, are given in Table 1. For each severity of injury (fatal, “serious bodily” and over-3-day) the table shows the proportions attributed to each type of accident. The final column in the table gives the number of reportable injuries (fatal plus serious) per 1000 over-3-day injuries, for each type of accident. The figures in this column demonstrate the remarkable differences in the propensity of each type of accident to produce serious injuries. In terms of these figures “haulage and transport” accidents have 48 times the propensity of “handling” accidents to produce serious injuries. This suggests that in the case of handling accidents, studies of minor injuries will highlight some different problems from those that cause serious injuries, but that in the case of haulage and transport accidents there may be some common problems. Because of the cumulative importance of accidents leading to minor injuries SEL, in conjunction with NCB, have conducted studies into their causation with the full involvement of Management, Unions, and the Mines Inspectorate. Two major problem areas have been studied: (i) Loss-of-balance accidents - a survey that covered all collieries within NCB Doncaster Area (i.e. about 18000 men); and (ii) Transport and handling accidents - a survey that covered six collieries TABLE
1
Distribution
of over3-day,
Type of accident
Haulage and transport (vehicles and conveyors) Machinery Struck by falling objects (includes falls of ground) Loss of balance (stumbling, falling 01 slipping) Use of tools and appliances Handling supplies, etc. Others (including disasters)
serious and fatal injuries in coal mines for 1972-1975 Percentage of all serious bodily injuries
Percentage of all fatalities
Number of fatal and serious injuries per 1000 over3-day injuries for each type of accident
8.1 4.8
37.3 8.3
36.7 8.6
48.3 18.2
23.6
27.7
24.2
12.2
24.3 9.3 17.6 12.3
14.7 3.7 1.7* 6.7
5.1 1.1 0.6* 23.6
Percentage of au over3-day injuries
6.0 3.9 1.0* 6.5
*The Mines and Quarries new accident classification. introduced in 1973, does not categorise “handling” accidents separately. These figures are based on the old classification statistics for the period 1970-1974.
307
(about 6000 men) within NCB North Derbyshire Area. (The term transport includes haulage operations and conveying.) Published statistics (e.g. see Table 1) show that these two categories taken together account for about half of the over-3-day injuries in British coal mines. 2. METHODS
USED BY SEL TO OBTAIN
INFORMATION
Apart from one table in the annual reports on Health and Safety in Mines and Quarries (e.g. Health and Safety Executive, 1976a) and similar ones published by NCB, no other information about the circumstances leading to minor injuries was (or is) routinely available to SEL. (This situation is likely to change following the introduction of proposed new regulations regarding the notification of accidents to HSE (Health and Safety Commission, 1979).) The first objective therefore was to acquire information that would further SEL’s understanding of the causes of accidents leading to minor injuries. For example in order to understand what causes people to fall, information is needed on such variables as the surfaces on which people walk, whether these are covered with a lubricating layer, etc, etc. Since accident reports made out at colliery level do not contain this amount of detail two methods have been investigated for obtaining the relevant information; a conventional questionnaire completed at interviews with the injured person and an automated device which presents questions on a screen and records answers (the questionnaire machine). 2.1 Conventional
questionnaires
As some thousands of accidents would be involved in the surveys, it was decided at the outset that none of the accidents would be physically investigated (in the sense of viewing the scene, calling on witnesses, etc.) and that reliance would be placed on statements made by the injured men themselves. The co-operation of the injured men was sought on a purely voluntary basis. It was felt that the chances of success would be low if the injured men were asked to complete questionnaires themselves. This view was subsequently reinforced by the poor response (27%) to a very simple questionnaire in which men were invited to express their opinions about an item of equipment about which there had been widespread complaints. A pilot experiment suggested that a system based on medical-room staff asking men questions and recording the answers would be unlikely to succeed. Accordingly, a system was agreed that depended on colliery Safety Officers, or a questionnaire machine (see Section 2.2), interviewing injured men. Accidents reportable to the Inspectorate of Mines and Quarries were, of course, excluded. To enable Safety Staff to select men for interview a scheme that utilized
308
standard NCB accident reports was adopted. Such reports are completed by the injured man’s immediate superior who then forwards them to the colliery Safety Officer (Friedman, 1975). It was arranged, therefore, that when one of these forms reached the safety office and the written description of the accident indicated that it was relevant to the investigation, the Safety Officer should try to arrange an interview with the injured man, regardless of whether time was lost from work or not. Arrangements were left to the discretion of individual Safety Officers; different methods were adopted at different collieries to suit local conditions. In the case of the transport and handling survey, printed notes of guidance, particularly in relation to the types of accident of interest, were provided by SEL. Each Safety Officer was supplied with a questionnaire booklet and a set of answer sheets (Appendix 1 shows an answer sheet used in the transport and handling survey) on which he was asked to record answers. The answer sheet was laid out to facilitate the recording of answers at the collieries, the coding of the information at SEL and the transference of data to punched card for computer input. The questionnaires were in three parts; Part 1 covered general information which the Safety Officer was asked to supply from details given on the standard NCB accident report from before the interview; Part 2 was designed to elicit the relevant facts from the respondent at the interview; and Part 3 gave the Safety Officer an opportunity to give his own views after the interview as to the causes of the accident and what remedial measures might be appropriate. Appendix 2 shows Part 3 of the questionnaire used in the transport and handling survey. At the interview the Safety Officer was to lend the injured person a booklet which contained an assurance (Appendix 3) that the information he gave would not be used against him by his employer; it also provided an aide memoire for some of the questions from Part 2 of the questionnaire. For each accident the Safety Officer was also asked to complete a small form giving the number of days lost, if any. (A separate form was used to avoid a delay in submitting answer sheets to SEL since the man could return to work several weeks after the interview.) 2. I. 1 Experience with the loss-of-balance questionnaire. Experience with the loss-of-balance questionnaire has already been described (Senneck, 197513). For the 23-month period of the survey the overall percentage inclusion of eligible cases was 64%, but. the response varied between collieries and with time. One colliery achieved 100% during the first six months: another had only a 13% return for a six-month period towards the end of the survey. Three collieries achieved more than an 80% response rate. Analysis of the data showed that Safety Staff completed the answer sheets reliably. Overall only 148 disallowed answers were recorded on 4303 answer sheets (the questionnaire having over 40 questionsj. Indeed the proportion of such answers for individual collieries did not correlate significantly with response, i.e. “more returns” does not imply “less reliable returns”. The main source
309
of error occurred where the questionnaire branched and all Safety Staff made mistakes in selecting appropriate follow-up questions. Although these errors did not give rise to difficulties in analysing the information it is recommended that the use of filter questions be avoided whenever possible. 2.1.2 Experience with the transport and handling questionnaire. Transport and handling accidents are more difficult to invest.igate than loss-of-balance accidents since the associated factors are usually more varied and their interrelationship more complicated. Thus most of the information regarding the circumstances and situations in which such accidents occurred was recorded in narrative form rather than preceded responses in order to achieve an interview of acceptable length. Appendix 4 shows the form the narrative questions took. Another feature introduced for this survey was the use of smallscale plans (see Fig. 1) on which Safety Staff marked the site of an accident. The questionnaire was subjected to a trial at a single colliery, with very satisfactory results. The response of the injured men was good, and each interview took between ten and fifteen minutes compared with about ten minutes for the loss-of-balance survey. One of the interesting features to emerge from the pilot trial of the questionnaire was that Safety Staff preferred an explicit, and hence more lengthy, list of possible contributory factors to a shorter one that required judgement to be exercised in selecting the appropriate code. A similar situation arises in classification schemes in which each accident has to be allocated to one, and only one, of a number of categories that are not so tightly defined as to be mutually exclusive. For example, suppose a man fell down while lifting a derailed tub back onto the track; this could be shown as involving haulage and transport, or manhandling, or loss of balance, if these were the categories available. The choice of category used would depend on the judgement of the person performing the classification. Thus in designing the survey, hybrid codes were used to analyse details of 2444 accidents since it was necessary to identify all accidents that were in any way associated with haulage and transport systems or handling supplies. For example, an accident in which a man tripped over a haulage rope was classified as LOB/HT rather than either loss of balance or haulage and transport. This considerably increased the number of accidents to be considered in the transport and handling group beyond that indicated by published statistics. About half of the accidents were found to be in this group when accidents involving loss-ofbalance were included and about a third if they were excluded (Health and Safety Executive, 1976b). 2.2 Questionnaire
machines
Three possible disadvantages associated with the use of conventional questionnaires in the way outlined above are: (i) Details of accidents not notified on standard report forms (i.e. those
310
.\ \
\ \
‘1
\
HIGH
‘1 ‘\
PIT
HAZEL BOTTOM
\
HIGH HAZEL
SEAM
T
Fig. 1. Example
of a colliery
plan. (Actual
plan printed
on A3-size
paper.)
311
trivial injuries recorded only at medical treatment centres) are not captured; (ii) Arranging and conducting interviews may be time-consuming for Safety Staff; and (iii) In view of 2.1 above, questionnaires of a highly branching nature (e.g. a general purpose accident questionnaire) would be unlikely to succeed. To overcome these disadvantages SEL developed a questionnaire machine which presents questions on a screen for the respondent to answer by speaking into a microphone or by pressing numbered buttons. Proctor (1977) has given a detailed description of the machine and discussed user acceptability, information quality, and accuracy. 2.2.1 Experience with the questionnaire machine. Questionnaire machines have been used at one large colliery in the Doncaster Area of NCB and at two small collieries in the North Derbyshire Area. Initially the machine was used in the medical treatment centres at two of the collieries and the experience gained has been published by Proctor (1974,1977) and Proctor and Cutts (1976). It was agreed by NCB Management, Unions, the Mines Inspectorate and SEL that men would be asked by the medical staff to participate in this type of project on a voluntary basis in their own time after treatment of their injuries (usually at the end of a shift); there was no suggestion that men who had sustained severe injuries (or injuries that would make it difficult for them to use the machine) should be asked to take part. An undertaking of confidentiality similar to that shown in Appendix 3 was displayed at the beginning of the questionnaire. As part of the trials the medical staff at the collieries were requested to keep records of the men who were asked to use the machine but who declined to do so for some reason. It has been calculated that at the first colliery 45% of those asked to use the machine agreed to do so, while the corresponding figure for the second colliery was over 80%. The number of men who actually took part largely depended on the level of enthusiasm maintained by the medical staff. At both collieries the numbers of men asked to participate fell during the trials but the proportion of those who agreed to take part stayed roughly constant at 45% and 80% respectively. In addition machines have been used at two collieries participating in the transport and handling survey. In this study the machine was in the charge of Safety Staff and located in a room adjacent to the safety office. One disadvantage of the technique is that Safety Staff do not get the useful pointers to accident prevention that they would if they conducted the interviews themselves. It was decided therefore that Part 2 of the answer sheet (Appendix 1) would be completed at SEL for each respondent and returned to the safety office for the completion of Part 3 (causes and remedies). (Since the decoding unit for the questionnaire machine separates the verbal messages from the coded responses an audio typist was able to type out the narratives.)
312 3. FINDINGS
AND DATA
3.1 Loss-of-balance
ANALYSIS
survey -follow-up
study of remedial measures
The findings from the study of loss-of-balance accidents are dealt with in some detail by Tregelles and Senneck (1973), Senneck (1975b) and Senneck and Nussey (1973). This study, which involved about 18,000 men at eleven collieries, underlined the difficulties that are likely to confront researchers conducting studies in real situations where changes in environment and procedures cannot be controlled. An example of the importance of taking such factors into account is provided by the part of the survey concerned with monitoring the effectiveness of boots fitted with tungsten-carbide tipped studs as a means of reducing the risk of slipping (Senneck and Nussey, 1973). Interim data analysis had shown that studded footwear was having an effect and the following extract was published in SMRE’s Annual Report for 1971 (Safety in Mines Research Establishment, 1972): When the numbers of accidents classed as “stumbling, falling or slipping” that occurred in 1970 were compared with those that occurred in 1969, it was found that the figures for the Doncaster Area had fallen by 18% more than the figures for the rest of the country. A difference as great as this would occur by chance less than one in a thousand times. There has been no corresponding change in the proportions of other accidents. Figures for 1971 for the rest of the country are not yet available, but the level in the Doncaster Area has remained low and correlates well with the number of men known to have studded boots.
When the data for certain other areas of the country were available a “Cusum” analysis (Woodward and Goldsmith, 1964) showed that other areas had also shown a reduction in the proportion of accidents attributed to loss-of-balance at the same time, but not to the same extent. It transpired that NCB had introduced a new sick-pay scheme at the time when the number of studded boots was becoming significant in Doncaster Area and that this tended to reduce the percentage of over-3-day accidents attributed to loss-of-balance. The effects of such external influences on the over-3-day accident rate have been discussed by Senneck (1975a). The final analysis took account of all reported loss-of-balance accidents regardless of whether or not time was lost and made use of the matched pairs technique; men being matched by job (because to some extent this determines the amount of activity involved) and colliery (because environmental conditions vary widely between collieries). Only men who had remained at the colliery throughout the survey were considered and members of the control group were randomly selected. Comparison of the accident experience of some 3461 matched pairs of men who between them had suffered almost 5000 loss-of-balance accidents showed that, overall tungsten-carbide studs fitted into new boots effected a 10% reduction in loss-of-balance accidents - more than sufficient to cover the cost of studding -but despite the considerable effort in collecting and
313
collating details of accidents and the writing of computer programmes to analyse the data this finding was not statistically significant. Comprehensive details of this analysis and the effects of the outside influences have already been published (Senneck and Nussey, 1973). Evidence acquired from the loss-of-balance questionnaire showed that in conditions where studs are likely to be effective, e.g. on hard surfaces covered by a thin lubricating layer, they reduce the number of slipping accidents by 47% (there are less than 3 chances in one hundred of such a difference arising be chance alone). It would seem, however, that such conditions were not sufficiently common for the studs to have a marked effect on the overall loss-of-balance accident rate. The work also made it clear that partially worn boots were not suitable for studding.
8.2 Use of supplementary
information
to support accident
data
An important aspect of data analysis is the use of supplementary information to enable meaningful data comparisons to be made (e.g. observed and expected frequencies) or for the calculation of accident rates. For example in the transport and handling survey (Health and Safety Executive, 1978a) details of standard NCB reports of minor accidents have been collected at SEL in order to assess the response to the survey to ensure that the data analyses are not affected by any selection bias, and to assess the injury potential of various jobs and operations. Almost half of the information collected relates to one large colliery employing 1400 men, where the survey ran for over two years. At this colliery the supplementary data show that haulage workers (i.e. those associated with vehicular transport underground), coal face workers and rippers sustain, on average, about one minor injury each year and one over-3-day injury every three years, that is, they are injured about twice as frequently as other underground workers and four times as frequently as surface workers. By way of another example, NCB method-study data for haulage teams at this colliery have been used to estimate the amount of time these men spend in performing various tasks, so that the likelihood of suffering minor injury whilst performing a given task can be determined. This analysis showed that although haulage workers suffer most injuries while loading, unloading or rerailing vehicles, the highest risk at this colliery (measured in terms of time of exposure) occurred when men were lockering vehicles, i.e. inserting a steel bar between the spokes of a vehicle wheel in order to park the vehicle or slow it down. The operations with the next highest risk of minor injury were clipping and unclipping vehicles on haulage ropes, loading or unloading vehicles and re-railing vehicles. 3.3 Data analysis -general
considerations
With regard to the more general aspect of data analysis there is no single
314
method of obtaining “the answer” and indeed there is unlikely to be a single “answer” to any particular type of accident. Because much of the information that has been collected by the questionnaires is qualitative rather than quantitative, the technique most widely used by SEL has been to classify the data by means of suitable coding techniques and then to cross-tabulate the incidence of accidents according to two or more variables. This process is interactive in that one set of tables suggests new hypotheses; a useful starting point has been to tabulate each variable by colliery to gain insight into significant factors and how they vary between collieries. Thus even in the absence of background exposure information, useful information can still be extracted since a careful examination of tables showing the frequency of occurrence can often suggest further questions that may be asked of the data. In some cases, it will be necessary to refer back to the narrative accounts of accidents to provide further understanding of the patterns that emerge from the tabulated data or to cope with ad hoc analyses that cannot be conducted within the framework of the chosen coding scheme. A full text searching document retrieval program (Price et al., 1974) is proving useful for these types of analysis. 3.4 Some findings
from the transport and handling
survey
Both surveys provided far more detailed and comparable information about accidents than was available from standard NCB accident report forms. In particular, the survey of transport and handling accidents is enabling the sequence of events leading up to the minor injuries to be identified. For example, the standard reports on injuries associated with re-railing vehicles seldom show why vehicles became derailed in the first place. The survey at the large colliery mentioned previously, where haulage is by rope systems, shows that about half the derailments were due to track faults, a quarter to situations that required vehicles to be deliberately moved off the track, and 12% were due to damaged vehicles. Again, only 2 out of the 18 situations examined, in which rope-hauled vehicles became (or might have become) jammed on road-side supports or equipment, etc., could be identified from the standard report. The sequence of events immediately preceding each injury or incident is triggered by what are essentially the main contributory causes of accidents. Of particular interest are the “first” events in such sequences and analysis of the 715 transport and handling accidents reported to SEL showed that over a third of these could be classified as system or mechanical malfunctions. Almost another third of such events for the total number of accidents reported were classified as loss-of-balance, and of these accidents 42% were associated with wet conditions and 32% with the transport system, for instance stumbling because of an unevenly ballasted rail track or tripping over a haulage rope. The “first” events classified as system or mechanical malfunctions have
315
been further broken down and the largest categories are as follows (the figures being expressed as percentages of the 715 accidents): vehicle derailments, 12%; haulage ropes either coming off pulleys, deflecting, holding fast or moving unexpectedly, 5%; situations where a vehicle was, or may have been, caught on road-side supports or equipment, etc., owing to lack of clearance, 4%; and vehicles moving out of close control or not stopping as expected, 4%. All these events were associated with rope haulage and resulted in minor injuries; however, similar events cause serious and fatal injuries each year in British coal mines (Health and Safety Executive, 1978b). In view of this, and the fact that the difference between an injury and a near miss is often a matter of chance, it should be possible to use information on “first” events as identified from reports of minor accidents and near misses to pinpoint blackspots, i.e. localities or situations where there are likely to be serious injuries unless preventive action is taken. Such action, being based on local information, may be more effective in reducing the number of serious injuries than prevention strategies based on national statistics. 3.4.1. Improved accident reporting procedures as an aid to accident prevention. Discussions with colliery Safety Staff indicated that they found the extra information useful for taking accident prevention measures. For example, at one of the collieries that took part in the survey, Safety Staff marked the locations of accidents on small-scale colliery plans with coloured pins to represent the five main reasons for transport and handling accidents identified by SEL. This procedure showed up a particular underground transfer point of the transport system as an accident black spot within the first three months of the survey. Action was taken and there was only one further accident at this location during the following six months. Safety Staff at this colliery estimate that remedial action has been taken in about half the cases where injured men have been interviewed. It seems reasonable to suppose that the more detailed completion of accident reports on minor injuries or near misses with the potential to produce serious injury would help Safety Staff in accident-prevention work at local levels. Such information would also enable plans showing the locations of accidents to be maintained, and if the detailed reports were filed by location the information needed to assist in the remedy of local accident blackspots would be readily available. At the colliery where plans have been used to show locations of accidents, and at other collieries that have been supplied with plans prepared by SEL showing accident locations by activity and suggested remedies, the Safety Staff have found such plans to be a useful means of communicating details of accident situations to Management and Safety Committees. The information could also be used to monitor the effectiveness of any changes made. (Following the conclusion of the survey some of the collieries in the area concerned are now utilising standard accident reports to enable them to easily maintain plans showing the locations of accidents for the identification of blackspots.)
316
The work has also indicated that the additional information can be obtained without large additional resources. Standard accident reports are normally completed by officials and it is estimated that, on average, each official completes an accident report about once a month. Experience has shown that, for the detailed survey, each interview takes 10 to 20 minutes including the time to write down the information on the questionnaire. It is not, of course, suggested that more detailed accident reports and data on near misses can replace management or engineering judgements, but the reports and data should provide insight into the appropriate solutions in much the same way as the findings of the very thorough investigations of serious and fatal injuries conducted by the Mines and Quarries Inspectorate can often be applied to prevent similar accidents occurring elsewhere within the industry. 3.4.2. Suggested remedies. In the course of the survey the injured men and the colliery Safety Staff were asked to suggest ways of preventing similar accidents from recurring and, in general, the views of men and Safety Staff were in good agreement. The Safety Staff made up to three suggestions for each accident; the ones analysed here are the first suggestions made since these showed the best agreement with those of injured persons and were concerned more often with physical than with human solutions. In the case of accidents attributed to system or mechanical malfunctions (representing more than a third of the total number of accidents), almost half of the suggestions related to better maintenance or better design of hardware, or to improvements in the surroundings, e.g. a better lay-out or more space; and a quarter related to the provision of additional equipment or to the use of available equipment such as lifting tackle. When the accidents attributed to loss of balance were directly associated with the transport system, almost two thirds of the suggestions were to improve the maintenance of the track and the surface underfoot, to improve the surroundings or to clean and tidy up. Where loss-of-balance accidents were directly associated with other factors, almost two thirds of the suggestions were to clean up water or mud, or to tidy up equipment etc. Over a quarter of the suggestions relating to all accidents were for men to be more careful, to avoid unsafe positions or to follow codes of practice. This, together with other remedies relating to the use of more experienced labour, improved supervision, etc., supports the assessment of accident causes made by colliery Safety Staff who considered that lack of reasonable care by someone, or unsafe methods or actions played a part in over a third of the accidents reported to SEL. Interim findings from the survey have already been presented by Inspectorate and SEL personnel to Safety Committees at the collieries involved with a view to stimulating remedial action. Some of the specific suggestions to reduce accidents, made at the meetings, were to raise and maintain the track standards of supplies haulage systems to those of manriding systems; to provide more training and close personal supervision for newly recruited haulage workers;
317
to keep the work place clean and tidy, particularly the 200 m of the mine roadway adjacent to coal faces; to improve the planning of new units and procedures by paying more attention to safety features and by involving representatives of the men who would be affected; and to hold more group discussions among the work-force on safety matters. The full findings from this survey are to be published (Nussey and Thompson, 1980). CONCLUSIONS
The work has made clear the following points: (1) British miners are prepared to participate in an interviewing system of the type described here provided that they are satisfied that there will be no unpleasant repercussions for them. (2) Most Safety Staff can organise a system of interviewing and can run it successfully for quite prolonged periods. (3) In the British coal mining industry, at least, such an interviewing system can provide much more detailed information about accidents leading to minor injury than is available from standard sources and is of use in furthering the understanding of the factors associated with such accidents. (4) Given management support, the information can be used to initiate remedial action or start investigations into particular problem areas. ACKNOWLEDGEMENT
The author wishes to thank the many members of NCB, Unions, the Mines Inspectorate and SEL who have co-operated and contributed advice and direct effort to the surveys. In particular he would like to acknowledge the support and encouragement given by the late C.R. Senneck during the greater part of this work. 0 Crown copyright reserved. REFERENCES Friedman, E., 1975. The Coal Board’s accident statistics, Paper E4, Proceedings of e Symposium on the Collection Analysis and Interpretation of Accident Data, Sheffield, 9-12 July, 1973. Health and Safety Commission, 1979. Consultative Document: Proposals for Notification of Accidents, Dangerous Occurrences, and Ill Health Regulations and Guidance Notes, HMSO, London. Health and Safety Executive, 1976a. Health and Safety: Mines and Quarries 1975. HMSO, London. Health and Safety Executive, 1976b. Health and Safety Research 1975. HMSO, London. Health and Safety Executive, 1978a. Health and Safety Research 1977. HMSO, London. Health and Safety Executive, 1978b. Health and Safety: Mines and Quarries 1977. HMSO, London. Nussey, C. and Thompson, H., to be published.
318 Price, N.H., Bye, C. and Niblett, B., 1974. One-line searching of Council of Europe conventions and agreements: A study in bilingual document retrieval. Inf. Storage Retr., 10: 145-154. Proctor, T.D., 1974. Progress report on the operation of the SMRE questionnaire machine at a small colliery. SMRE Technical Paper Pll. Proctor, T.D., 1977. A questionnaire machine for collecting accident data. J. Occup. Accidents, 1: 113-l 22. Proctor, T.D. and Cutts, N.J., 1976. A novel method of collecting information. Occup. Health, 28: 302-307. Robens, Lord, 1972. Report of the Committee on Safety and Health at Work, HMSO Cmnd 5034. HMSO, London. Safety in Mines Research Establishment, 1972. Safety in Mines Research 1971: Fiftieth Annual Report 1972. HMSO, London. Senneck, C.R., 1975a. Over-3-day absences and safety. Appl. Ergonomics, 6(3): 147153. Senneck, C.R., 197513. Experimental use of a paper questionnaire. Paper C5, Proceedings of a Symposium on the Collection, Analysis and Interpretation of Accident Data, Sheffield, 9-12 July 1973. Senneck, CR. and Nussey, C., 1973. Experience in NCB Doncaster Area with boots fitted with tungsten-carbide tipped studs. SMRE Technical Paper P4. Tregelles, P.G. and Senneck, C.R., 1973. A new approach to accident investigation in the Doncaster Area: An interim report. Mining Engineer, 150 (March): 291-327. Woodward, R.H. and Goldsmith, P.L., 1964. Cumulative Sum Techniques. ICI Monograph No. 3. Oliver and Boyd, Edinburgh.
319 APPENDIX
NCBISMRE
HAULAGE AND HANDLING
ANSWER
85
SHEET
86
Tsme 01accide”,
1
: PART 1 (SAFETY
ACCIDENT
OFFICER
SURVEY
-FROM
ARI)
Job 0”da” PART 2 (INTERVIEWER)
12
I-12 19
20
23,
24,
27
26
AlrI A,,
AlI\
,“,,,a15
I-12
PART 3 (SAFETY
Oale SMRE
OFFICER)
A,ii”l A2[25,
26,
Sayrhat
Flee
say “hat
Coded
say *a,
Punched
A2rl SMRE
USE ONLY
USE ONLY
320
APPENDIX
2
the
To be completed by the Safety Officer after the interview, answers written on the answer sheet.
Al.
PART 3
taking account of
What factors do you think probably helped to cause the accident? (Choose UP to three answers - one in each pair of boxes marked Al) Defective or signal
deslgned tools/equ ipment/suppl i&clothing/safety
or poorly
I ing device
I
__.~. __.....____..... ____..... ___..., _____ ~__ _____. _____ _._..___...._..._............._..... 0 1
Defective
or inadequately
Defective
or poorly designed
vehicles
Defective
or poorly
surroundings
installed
designed
rail track
..__ __......___......_.. .. ..
. .......~_.. 0
2
... ...._..... _....._......... . tti0
3
(clearances,
heat, water etc) .__ 16141
Failure to use available tooIsiequipmentlsuppties/ctothing/safety or signal Ling deviice __ ____.____. ___..___,.___._.._._... __._...__..... _____.._____________................................... 16151 Failure
of mechanical/electrical/safety
tnadequate
instruction/supervision
Inadequate
training
or signal .~~. .. .
t ing device
__~.....~~...
0 6 LLJ
.~ . ~~. .. ......._.................. _._._ . ...... .
_.________.____ ____.___________________ _.______..._.___..__..........................................
Lack of suitable tools/equipment/supplies/clothing/safety or signalllng ........................................................................................................................... device Lack of suitable
0
9
.........................................................................................
1
0
......................................................................................................
1
1
...........................................................
1
2
..........................................................
1 III
3
vehicles
Lack of experience Lack of reasonable
care by injured
person
Lack of reasonable
care by someone else
Misuse
of tools/equipment/supplies/clothing/safety
Misuse
of vehicles
Signal
device
......................................................................................................
misunderstood
Untidiness
or signalling
................................................................................................
q 1
4
1
5
1 m
6
1 7 .......................................................................... I
or poor housekeeping
Unsafe method of work not actively
discouraged by supervlsors ................................................................................................................
(egdeputies) Unsafe
action
by injured
person
Unsafe
action
by someone else
1
8
1
9
2
0
2 ccl
1
.............................................................................. ...............................................................................
...........................................................................................
B
Some other known
cause
No known cause
,___._____.____._.._............................................................... _.........._........._.
321 APPENDIX
2 cant
AZ. What do you think could be done to prevent
a similar accident happening again? (Choose up to three answers - one in each pair of boxes marked A2. appropriajezritten clarification alongside the coded boxes).
Clean or tidy
up:
Provision
Water _.__._..__...__ _________._._.__ _____ __ _____ __. Mud _____.._.________._._......._.... __..._ _____ a... Coal ________. _.,_..._____ _.________.... _.___.__.__ Stone or dirt _._____ ___,______ _.____._ ____ ____. Tool(s) ____.___________.. ____________.___.. ____._ Usable material ______________. ___._ _______ Scrap ___..__. _____ __.___ ___.____....__... ____.___... Equipment Something
(incl else
Better maintenance/repairs
of:
__._....
Locker/Stang/Scotch __.____. ____._.__._____..__. .._.._..._._._.._.__....... _____ __.___._.._.__ _ Loadbinder tool ______ __._ _....___. __.... __. Hand tool/Power Lifting equipment . ..____ ___.._ _.________.____.__._.___ clothing _____._______._ . ... __.._ ._._ ____. Protective Vehicle/Haulage rope/Conveyor ..._._.. _______ ___.____ __ Signalling or safety device Equipment/mechanical aid __......_._._....... Something else - -say what ._.___ .___.._.. _...
on:
Make the surroundings:
cables/hoses)..
- say what --
Where
____._..___._____.____ _____. . ..-..._.-..-.. -.-_Rail track _ ______________________.._____._..~.Less noisy _________________.~...-....*.-..-..~---. Toot (include locker & stang) ___ Better I ighted _.._______.______._.__________I______ Lifting equipment . .._______ _..._____ ___... Hotter or cooler .._______&__________________.._..._~-------..Vehicles__...___ ___._______._.___... _. .._._..... Less dusty ___._._----. __._-......... Less humid _______.__.______.____ Haulage rope _.._._...___._____ _____ __._.. __.. ___.____..__ _..-_... _____.----.-.. . ..--.--------Mot-e humid ______ _... Conveyor/Bunker/Chutes _._____._._.__.___..-..--- __.-...---.--.More spacious Signalling or safety device ..._. _.. la id out _______ ._._.._____. . . . . . . . .._.... ..---.-Better Surface underfoot (incl steps) -.-_-..-_I-_.___=_W-‘. Something else say what Something else - say what _______... --
Use of available:
Less
Locker/Stang/Scotch ___ _.._ ___..__ _._. Loadbinder ._.....____________ ______ _.__ _._._.____ Hand tools/Power tools _.___ _____ _._. Lifting equipment _._..__________ _.______.. Protective clothing __._.__ __.__ _.._._.... Vehicle/Haulage rope/Conveyor Signalling or safety device _______ Equipment/mechanical aid ___.______ Something else - say what ._.______. --
____ ___._______ _______________ Getting off the shift Getting on/off rranrider or cage _______.. ___ .______.__ _. In carrying out the job _____.______ To finish job so another can start ____ To get the job moving again _....__._..._... To get to the baths ___.___ ____ ___.__ ____.____ _____., .____ ____ _.___________.__ ____. To get to the job ____..__ ______._ __.._____ .._._ To avoid a hazard _.__..._ Some other reason - -say what ___________.__
Better design/construction
Other remedies:
of:
Locker/Stang/Scotch __.__._ __._., Loadbinder ._____.___ __.___________._...__.. Hand tools/Power tools __.._ __.__ __.
Lifting equipment __..______._.____.__.. Protective clothing _____._______. ____. Vehicle/Haulage rope/Conveyor Signall ing or safety device ______ Equipment/mechanical aid __. Something else - say what __.... -Nothing
think
Please add a written it would help.
haste:
.. .._____._....._____~~..~~~~.... Better supervision __._ ___. Use more men on the job ______._______ Use more experienced men ___________________ Avoid awkward or unsafe positions ___ Make better use of hands or body ____ Follow recommended codes of practice Pay more attention to signals Do job at different time or place ______._. Something else could be done - -I_ say what
could he done
clarification
- 80
on the back
of the answer
sheet
if you
322
APPENDIX
3 I
PAGE
NCB/SMRE
HAULAGE
INJURED
AND HANDLING
ACCIDENT
PERSONk
1
SURVEY
BOOKLET
We all want to stop accidents!
You can help by arlswering
Your answers
will
and on no account
a few simple questions.
be treated will
in strict
confidence
they be used against
you
by your employer
The information will be used by scientists into the cause of accidents.
Please help by answering
as carefully
looking
as you can.
323
APPENDIX
4
The next three questions are particularly NOTE TO THE INTERVIEWER please write down all the points he mentions and avoid the temptation too much. Don’t put words into his mouth but, if necessary,
important; to abbreviate
ask him questions to clarify
or fill out his statement.
10.
“Turn
to page 10.”
,....
“What
activity
were
you engaged in when you had
your accident?” Get the t&asJ he was deployed Get his activity
to that shift
(not occupation)
Get him to name any tools, Get him to name anything
in space marked
10,
appliances,
etc. that he was using.
that he was working
naming the objects,
11. “Turn to page 11.” . . . . . “Please describe Please step by step what happened next. pa in your accident.” Find out and write
in the space marked
how the accident
started
on.
YET.
etc.
how your accident name anything
that
11:
next,
ending
with
hurt him
(naming everything, including defects of objects, environment etc. that played a part).
Do not write about his activity describing his accident.
12.
at length
unless
in space marked
12.
roadway,
it is essential
“What do you think could be done to prevent an accident
Write suggestions
started and played a
and
step by step what happened ---_ how he was hurt and w&
19’s gate conveyor
at the time.
00 NOT LET HIM DESCRIBE HIS ACCIDENT
Write answer
eg repairing
for
like yours happening again?”
Do not give him ideas.
305 -
Printed
in Belgium.
STUDIES OF ACCIDENTS LEADING TO MINOR INJURIES IN THE U.K. COAL MINING INDUSTRY *
CLIVE
Safety Safety
NUSSEY
Engineering Laboratory, Research and Laboratory Executive, Red Hill, Sheffield S3 7HQ (U.K.)
(Received
November
13, 1979;
accepted
21 November
Services Division,
Health and
1979)
ABSTRACT Nussey, C., 1980. Studies of accidents leading to minor injuries industry. Journal of Occupational Accidents, 2: 305-323.
in the U.K. coal mining
The Safety Engineering Laboratory (SEL) (part of the former Safety in Mines Research Establishment, SMRE) of the Health and Safety Executive (HSE) has recently participated in two field studies of accidents among British coal miners. The studies have been carried out in cooperation with the National Coal Board (NCB) and have concentrated on accidents leading to relatively minor injuries, i.e. those involving absences for more than three working days (some 50,000 each year) and less severe injuries. The paper describes and discusses the methods employed (including the use of a questionnaire machine) to collect fairly detailed information directly from individuals who had suffered minor injuries, with a view to identifying causative factors; outlines some of the techniques that have been used to analyse the data; and reviews some of the findings.
1. IMPORTANCE
OF MINOR
INJURIES
The report on Health and Safety in Mines and Quarries for 1975 (Health and Safety Executive, 1976a) shows that, between the years 1972 and 1975, 256 men were killed and 2155 suffered “serious bodily” injury in British coal mines. Such severe injuries are reportable to the Inspectorate of Mines and Quarries. Over the same period, the report shows that there were 228,099 less severe injuries for which men were absent from work for more than three days (over-3-day injuries). Other work (Tregelles and Senneck, 1973; Proctor. 1974) suggests that injuries requiring treatment at colliery medical centres are about five times as frequent as over-3-day injuries. In terms of numbers alone these “minor” injuries (including over-3-day) are a significant problem in the mining industry; indeed apart from the aggregate pain and suffering involved they represent a considerable proportion of the *Based on a paper presented at the Seminar on Occupational Accident Research, Haikko, Finland, 13-17 November 1978. (Proceedings to be published by the Institute of Occupational Health, Finland.)
306
direct cost to the National Coal Board (NCB) of all accidents (Robens, 1972; Tregelles and Senneck, 1973). Because of the large numbers of minor injuries, it is probable that studies of the circumstances in which they occur will highlight some common problems, and some that are different from those leading to serious injuries. Insight into this latter aspect of minor injury causation can be derived from a study of the numbers (or proportions) of different types of accident at different severity levels. Such figures, derived from the report on Health and Safety in Mines and Quarries 1975, are given in Table 1. For each severity of injury (fatal, “serious bodily” and over-3-day) the table shows the proportions attributed to each type of accident. The final column in the table gives the number of reportable injuries (fatal plus serious) per 1000 over-3-day injuries, for each type of accident. The figures in this column demonstrate the remarkable differences in the propensity of each type of accident to produce serious injuries. In terms of these figures “haulage and transport” accidents have 48 times the propensity of “handling” accidents to produce serious injuries. This suggests that in the case of handling accidents, studies of minor injuries will highlight some different problems from those that cause serious injuries, but that in the case of haulage and transport accidents there may be some common problems. Because of the cumulative importance of accidents leading to minor injuries SEL, in conjunction with NCB, have conducted studies into their causation with the full involvement of Management, Unions, and the Mines Inspectorate. Two major problem areas have been studied: (i) Loss-of-balance accidents - a survey that covered all collieries within NCB Doncaster Area (i.e. about 18000 men); and (ii) Transport and handling accidents - a survey that covered six collieries TABLE
1
Distribution
of over3-day,
Type of accident
Haulage and transport (vehicles and conveyors) Machinery Struck by falling objects (includes falls of ground) Loss of balance (stumbling, falling 01 slipping) Use of tools and appliances Handling supplies, etc. Others (including disasters)
serious and fatal injuries in coal mines for 1972-1975 Percentage of all serious bodily injuries
Percentage of all fatalities
Number of fatal and serious injuries per 1000 over3-day injuries for each type of accident
8.1 4.8
37.3 8.3
36.7 8.6
48.3 18.2
23.6
27.7
24.2
12.2
24.3 9.3 17.6 12.3
14.7 3.7 1.7* 6.7
5.1 1.1 0.6* 23.6
Percentage of au over3-day injuries
6.0 3.9 1.0* 6.5
*The Mines and Quarries new accident classification. introduced in 1973, does not categorise “handling” accidents separately. These figures are based on the old classification statistics for the period 1970-1974.
307
(about 6000 men) within NCB North Derbyshire Area. (The term transport includes haulage operations and conveying.) Published statistics (e.g. see Table 1) show that these two categories taken together account for about half of the over-3-day injuries in British coal mines. 2. METHODS
USED BY SEL TO OBTAIN
INFORMATION
Apart from one table in the annual reports on Health and Safety in Mines and Quarries (e.g. Health and Safety Executive, 1976a) and similar ones published by NCB, no other information about the circumstances leading to minor injuries was (or is) routinely available to SEL. (This situation is likely to change following the introduction of proposed new regulations regarding the notification of accidents to HSE (Health and Safety Commission, 1979).) The first objective therefore was to acquire information that would further SEL’s understanding of the causes of accidents leading to minor injuries. For example in order to understand what causes people to fall, information is needed on such variables as the surfaces on which people walk, whether these are covered with a lubricating layer, etc, etc. Since accident reports made out at colliery level do not contain this amount of detail two methods have been investigated for obtaining the relevant information; a conventional questionnaire completed at interviews with the injured person and an automated device which presents questions on a screen and records answers (the questionnaire machine). 2.1 Conventional
questionnaires
As some thousands of accidents would be involved in the surveys, it was decided at the outset that none of the accidents would be physically investigated (in the sense of viewing the scene, calling on witnesses, etc.) and that reliance would be placed on statements made by the injured men themselves. The co-operation of the injured men was sought on a purely voluntary basis. It was felt that the chances of success would be low if the injured men were asked to complete questionnaires themselves. This view was subsequently reinforced by the poor response (27%) to a very simple questionnaire in which men were invited to express their opinions about an item of equipment about which there had been widespread complaints. A pilot experiment suggested that a system based on medical-room staff asking men questions and recording the answers would be unlikely to succeed. Accordingly, a system was agreed that depended on colliery Safety Officers, or a questionnaire machine (see Section 2.2), interviewing injured men. Accidents reportable to the Inspectorate of Mines and Quarries were, of course, excluded. To enable Safety Staff to select men for interview a scheme that utilized
308
standard NCB accident reports was adopted. Such reports are completed by the injured man’s immediate superior who then forwards them to the colliery Safety Officer (Friedman, 1975). It was arranged, therefore, that when one of these forms reached the safety office and the written description of the accident indicated that it was relevant to the investigation, the Safety Officer should try to arrange an interview with the injured man, regardless of whether time was lost from work or not. Arrangements were left to the discretion of individual Safety Officers; different methods were adopted at different collieries to suit local conditions. In the case of the transport and handling survey, printed notes of guidance, particularly in relation to the types of accident of interest, were provided by SEL. Each Safety Officer was supplied with a questionnaire booklet and a set of answer sheets (Appendix 1 shows an answer sheet used in the transport and handling survey) on which he was asked to record answers. The answer sheet was laid out to facilitate the recording of answers at the collieries, the coding of the information at SEL and the transference of data to punched card for computer input. The questionnaires were in three parts; Part 1 covered general information which the Safety Officer was asked to supply from details given on the standard NCB accident report from before the interview; Part 2 was designed to elicit the relevant facts from the respondent at the interview; and Part 3 gave the Safety Officer an opportunity to give his own views after the interview as to the causes of the accident and what remedial measures might be appropriate. Appendix 2 shows Part 3 of the questionnaire used in the transport and handling survey. At the interview the Safety Officer was to lend the injured person a booklet which contained an assurance (Appendix 3) that the information he gave would not be used against him by his employer; it also provided an aide memoire for some of the questions from Part 2 of the questionnaire. For each accident the Safety Officer was also asked to complete a small form giving the number of days lost, if any. (A separate form was used to avoid a delay in submitting answer sheets to SEL since the man could return to work several weeks after the interview.) 2. I. 1 Experience with the loss-of-balance questionnaire. Experience with the loss-of-balance questionnaire has already been described (Senneck, 197513). For the 23-month period of the survey the overall percentage inclusion of eligible cases was 64%, but. the response varied between collieries and with time. One colliery achieved 100% during the first six months: another had only a 13% return for a six-month period towards the end of the survey. Three collieries achieved more than an 80% response rate. Analysis of the data showed that Safety Staff completed the answer sheets reliably. Overall only 148 disallowed answers were recorded on 4303 answer sheets (the questionnaire having over 40 questionsj. Indeed the proportion of such answers for individual collieries did not correlate significantly with response, i.e. “more returns” does not imply “less reliable returns”. The main source
309
of error occurred where the questionnaire branched and all Safety Staff made mistakes in selecting appropriate follow-up questions. Although these errors did not give rise to difficulties in analysing the information it is recommended that the use of filter questions be avoided whenever possible. 2.1.2 Experience with the transport and handling questionnaire. Transport and handling accidents are more difficult to invest.igate than loss-of-balance accidents since the associated factors are usually more varied and their interrelationship more complicated. Thus most of the information regarding the circumstances and situations in which such accidents occurred was recorded in narrative form rather than preceded responses in order to achieve an interview of acceptable length. Appendix 4 shows the form the narrative questions took. Another feature introduced for this survey was the use of smallscale plans (see Fig. 1) on which Safety Staff marked the site of an accident. The questionnaire was subjected to a trial at a single colliery, with very satisfactory results. The response of the injured men was good, and each interview took between ten and fifteen minutes compared with about ten minutes for the loss-of-balance survey. One of the interesting features to emerge from the pilot trial of the questionnaire was that Safety Staff preferred an explicit, and hence more lengthy, list of possible contributory factors to a shorter one that required judgement to be exercised in selecting the appropriate code. A similar situation arises in classification schemes in which each accident has to be allocated to one, and only one, of a number of categories that are not so tightly defined as to be mutually exclusive. For example, suppose a man fell down while lifting a derailed tub back onto the track; this could be shown as involving haulage and transport, or manhandling, or loss of balance, if these were the categories available. The choice of category used would depend on the judgement of the person performing the classification. Thus in designing the survey, hybrid codes were used to analyse details of 2444 accidents since it was necessary to identify all accidents that were in any way associated with haulage and transport systems or handling supplies. For example, an accident in which a man tripped over a haulage rope was classified as LOB/HT rather than either loss of balance or haulage and transport. This considerably increased the number of accidents to be considered in the transport and handling group beyond that indicated by published statistics. About half of the accidents were found to be in this group when accidents involving loss-ofbalance were included and about a third if they were excluded (Health and Safety Executive, 1976b). 2.2 Questionnaire
machines
Three possible disadvantages associated with the use of conventional questionnaires in the way outlined above are: (i) Details of accidents not notified on standard report forms (i.e. those
310
.\ \
\ \
‘1
\
HIGH
‘1 ‘\
PIT
HAZEL BOTTOM
\
HIGH HAZEL
SEAM
T
Fig. 1. Example
of a colliery
plan. (Actual
plan printed
on A3-size
paper.)
311
trivial injuries recorded only at medical treatment centres) are not captured; (ii) Arranging and conducting interviews may be time-consuming for Safety Staff; and (iii) In view of 2.1 above, questionnaires of a highly branching nature (e.g. a general purpose accident questionnaire) would be unlikely to succeed. To overcome these disadvantages SEL developed a questionnaire machine which presents questions on a screen for the respondent to answer by speaking into a microphone or by pressing numbered buttons. Proctor (1977) has given a detailed description of the machine and discussed user acceptability, information quality, and accuracy. 2.2.1 Experience with the questionnaire machine. Questionnaire machines have been used at one large colliery in the Doncaster Area of NCB and at two small collieries in the North Derbyshire Area. Initially the machine was used in the medical treatment centres at two of the collieries and the experience gained has been published by Proctor (1974,1977) and Proctor and Cutts (1976). It was agreed by NCB Management, Unions, the Mines Inspectorate and SEL that men would be asked by the medical staff to participate in this type of project on a voluntary basis in their own time after treatment of their injuries (usually at the end of a shift); there was no suggestion that men who had sustained severe injuries (or injuries that would make it difficult for them to use the machine) should be asked to take part. An undertaking of confidentiality similar to that shown in Appendix 3 was displayed at the beginning of the questionnaire. As part of the trials the medical staff at the collieries were requested to keep records of the men who were asked to use the machine but who declined to do so for some reason. It has been calculated that at the first colliery 45% of those asked to use the machine agreed to do so, while the corresponding figure for the second colliery was over 80%. The number of men who actually took part largely depended on the level of enthusiasm maintained by the medical staff. At both collieries the numbers of men asked to participate fell during the trials but the proportion of those who agreed to take part stayed roughly constant at 45% and 80% respectively. In addition machines have been used at two collieries participating in the transport and handling survey. In this study the machine was in the charge of Safety Staff and located in a room adjacent to the safety office. One disadvantage of the technique is that Safety Staff do not get the useful pointers to accident prevention that they would if they conducted the interviews themselves. It was decided therefore that Part 2 of the answer sheet (Appendix 1) would be completed at SEL for each respondent and returned to the safety office for the completion of Part 3 (causes and remedies). (Since the decoding unit for the questionnaire machine separates the verbal messages from the coded responses an audio typist was able to type out the narratives.)
312 3. FINDINGS
AND DATA
3.1 Loss-of-balance
ANALYSIS
survey -follow-up
study of remedial measures
The findings from the study of loss-of-balance accidents are dealt with in some detail by Tregelles and Senneck (1973), Senneck (1975b) and Senneck and Nussey (1973). This study, which involved about 18,000 men at eleven collieries, underlined the difficulties that are likely to confront researchers conducting studies in real situations where changes in environment and procedures cannot be controlled. An example of the importance of taking such factors into account is provided by the part of the survey concerned with monitoring the effectiveness of boots fitted with tungsten-carbide tipped studs as a means of reducing the risk of slipping (Senneck and Nussey, 1973). Interim data analysis had shown that studded footwear was having an effect and the following extract was published in SMRE’s Annual Report for 1971 (Safety in Mines Research Establishment, 1972): When the numbers of accidents classed as “stumbling, falling or slipping” that occurred in 1970 were compared with those that occurred in 1969, it was found that the figures for the Doncaster Area had fallen by 18% more than the figures for the rest of the country. A difference as great as this would occur by chance less than one in a thousand times. There has been no corresponding change in the proportions of other accidents. Figures for 1971 for the rest of the country are not yet available, but the level in the Doncaster Area has remained low and correlates well with the number of men known to have studded boots.
When the data for certain other areas of the country were available a “Cusum” analysis (Woodward and Goldsmith, 1964) showed that other areas had also shown a reduction in the proportion of accidents attributed to loss-of-balance at the same time, but not to the same extent. It transpired that NCB had introduced a new sick-pay scheme at the time when the number of studded boots was becoming significant in Doncaster Area and that this tended to reduce the percentage of over-3-day accidents attributed to loss-of-balance. The effects of such external influences on the over-3-day accident rate have been discussed by Senneck (1975a). The final analysis took account of all reported loss-of-balance accidents regardless of whether or not time was lost and made use of the matched pairs technique; men being matched by job (because to some extent this determines the amount of activity involved) and colliery (because environmental conditions vary widely between collieries). Only men who had remained at the colliery throughout the survey were considered and members of the control group were randomly selected. Comparison of the accident experience of some 3461 matched pairs of men who between them had suffered almost 5000 loss-of-balance accidents showed that, overall tungsten-carbide studs fitted into new boots effected a 10% reduction in loss-of-balance accidents - more than sufficient to cover the cost of studding -but despite the considerable effort in collecting and
313
collating details of accidents and the writing of computer programmes to analyse the data this finding was not statistically significant. Comprehensive details of this analysis and the effects of the outside influences have already been published (Senneck and Nussey, 1973). Evidence acquired from the loss-of-balance questionnaire showed that in conditions where studs are likely to be effective, e.g. on hard surfaces covered by a thin lubricating layer, they reduce the number of slipping accidents by 47% (there are less than 3 chances in one hundred of such a difference arising be chance alone). It would seem, however, that such conditions were not sufficiently common for the studs to have a marked effect on the overall loss-of-balance accident rate. The work also made it clear that partially worn boots were not suitable for studding.
8.2 Use of supplementary
information
to support accident
data
An important aspect of data analysis is the use of supplementary information to enable meaningful data comparisons to be made (e.g. observed and expected frequencies) or for the calculation of accident rates. For example in the transport and handling survey (Health and Safety Executive, 1978a) details of standard NCB reports of minor accidents have been collected at SEL in order to assess the response to the survey to ensure that the data analyses are not affected by any selection bias, and to assess the injury potential of various jobs and operations. Almost half of the information collected relates to one large colliery employing 1400 men, where the survey ran for over two years. At this colliery the supplementary data show that haulage workers (i.e. those associated with vehicular transport underground), coal face workers and rippers sustain, on average, about one minor injury each year and one over-3-day injury every three years, that is, they are injured about twice as frequently as other underground workers and four times as frequently as surface workers. By way of another example, NCB method-study data for haulage teams at this colliery have been used to estimate the amount of time these men spend in performing various tasks, so that the likelihood of suffering minor injury whilst performing a given task can be determined. This analysis showed that although haulage workers suffer most injuries while loading, unloading or rerailing vehicles, the highest risk at this colliery (measured in terms of time of exposure) occurred when men were lockering vehicles, i.e. inserting a steel bar between the spokes of a vehicle wheel in order to park the vehicle or slow it down. The operations with the next highest risk of minor injury were clipping and unclipping vehicles on haulage ropes, loading or unloading vehicles and re-railing vehicles. 3.3 Data analysis -general
considerations
With regard to the more general aspect of data analysis there is no single
314
method of obtaining “the answer” and indeed there is unlikely to be a single “answer” to any particular type of accident. Because much of the information that has been collected by the questionnaires is qualitative rather than quantitative, the technique most widely used by SEL has been to classify the data by means of suitable coding techniques and then to cross-tabulate the incidence of accidents according to two or more variables. This process is interactive in that one set of tables suggests new hypotheses; a useful starting point has been to tabulate each variable by colliery to gain insight into significant factors and how they vary between collieries. Thus even in the absence of background exposure information, useful information can still be extracted since a careful examination of tables showing the frequency of occurrence can often suggest further questions that may be asked of the data. In some cases, it will be necessary to refer back to the narrative accounts of accidents to provide further understanding of the patterns that emerge from the tabulated data or to cope with ad hoc analyses that cannot be conducted within the framework of the chosen coding scheme. A full text searching document retrieval program (Price et al., 1974) is proving useful for these types of analysis. 3.4 Some findings
from the transport and handling
survey
Both surveys provided far more detailed and comparable information about accidents than was available from standard NCB accident report forms. In particular, the survey of transport and handling accidents is enabling the sequence of events leading up to the minor injuries to be identified. For example, the standard reports on injuries associated with re-railing vehicles seldom show why vehicles became derailed in the first place. The survey at the large colliery mentioned previously, where haulage is by rope systems, shows that about half the derailments were due to track faults, a quarter to situations that required vehicles to be deliberately moved off the track, and 12% were due to damaged vehicles. Again, only 2 out of the 18 situations examined, in which rope-hauled vehicles became (or might have become) jammed on road-side supports or equipment, etc., could be identified from the standard report. The sequence of events immediately preceding each injury or incident is triggered by what are essentially the main contributory causes of accidents. Of particular interest are the “first” events in such sequences and analysis of the 715 transport and handling accidents reported to SEL showed that over a third of these could be classified as system or mechanical malfunctions. Almost another third of such events for the total number of accidents reported were classified as loss-of-balance, and of these accidents 42% were associated with wet conditions and 32% with the transport system, for instance stumbling because of an unevenly ballasted rail track or tripping over a haulage rope. The “first” events classified as system or mechanical malfunctions have
315
been further broken down and the largest categories are as follows (the figures being expressed as percentages of the 715 accidents): vehicle derailments, 12%; haulage ropes either coming off pulleys, deflecting, holding fast or moving unexpectedly, 5%; situations where a vehicle was, or may have been, caught on road-side supports or equipment, etc., owing to lack of clearance, 4%; and vehicles moving out of close control or not stopping as expected, 4%. All these events were associated with rope haulage and resulted in minor injuries; however, similar events cause serious and fatal injuries each year in British coal mines (Health and Safety Executive, 1978b). In view of this, and the fact that the difference between an injury and a near miss is often a matter of chance, it should be possible to use information on “first” events as identified from reports of minor accidents and near misses to pinpoint blackspots, i.e. localities or situations where there are likely to be serious injuries unless preventive action is taken. Such action, being based on local information, may be more effective in reducing the number of serious injuries than prevention strategies based on national statistics. 3.4.1. Improved accident reporting procedures as an aid to accident prevention. Discussions with colliery Safety Staff indicated that they found the extra information useful for taking accident prevention measures. For example, at one of the collieries that took part in the survey, Safety Staff marked the locations of accidents on small-scale colliery plans with coloured pins to represent the five main reasons for transport and handling accidents identified by SEL. This procedure showed up a particular underground transfer point of the transport system as an accident black spot within the first three months of the survey. Action was taken and there was only one further accident at this location during the following six months. Safety Staff at this colliery estimate that remedial action has been taken in about half the cases where injured men have been interviewed. It seems reasonable to suppose that the more detailed completion of accident reports on minor injuries or near misses with the potential to produce serious injury would help Safety Staff in accident-prevention work at local levels. Such information would also enable plans showing the locations of accidents to be maintained, and if the detailed reports were filed by location the information needed to assist in the remedy of local accident blackspots would be readily available. At the colliery where plans have been used to show locations of accidents, and at other collieries that have been supplied with plans prepared by SEL showing accident locations by activity and suggested remedies, the Safety Staff have found such plans to be a useful means of communicating details of accident situations to Management and Safety Committees. The information could also be used to monitor the effectiveness of any changes made. (Following the conclusion of the survey some of the collieries in the area concerned are now utilising standard accident reports to enable them to easily maintain plans showing the locations of accidents for the identification of blackspots.)
316
The work has also indicated that the additional information can be obtained without large additional resources. Standard accident reports are normally completed by officials and it is estimated that, on average, each official completes an accident report about once a month. Experience has shown that, for the detailed survey, each interview takes 10 to 20 minutes including the time to write down the information on the questionnaire. It is not, of course, suggested that more detailed accident reports and data on near misses can replace management or engineering judgements, but the reports and data should provide insight into the appropriate solutions in much the same way as the findings of the very thorough investigations of serious and fatal injuries conducted by the Mines and Quarries Inspectorate can often be applied to prevent similar accidents occurring elsewhere within the industry. 3.4.2. Suggested remedies. In the course of the survey the injured men and the colliery Safety Staff were asked to suggest ways of preventing similar accidents from recurring and, in general, the views of men and Safety Staff were in good agreement. The Safety Staff made up to three suggestions for each accident; the ones analysed here are the first suggestions made since these showed the best agreement with those of injured persons and were concerned more often with physical than with human solutions. In the case of accidents attributed to system or mechanical malfunctions (representing more than a third of the total number of accidents), almost half of the suggestions related to better maintenance or better design of hardware, or to improvements in the surroundings, e.g. a better lay-out or more space; and a quarter related to the provision of additional equipment or to the use of available equipment such as lifting tackle. When the accidents attributed to loss of balance were directly associated with the transport system, almost two thirds of the suggestions were to improve the maintenance of the track and the surface underfoot, to improve the surroundings or to clean and tidy up. Where loss-of-balance accidents were directly associated with other factors, almost two thirds of the suggestions were to clean up water or mud, or to tidy up equipment etc. Over a quarter of the suggestions relating to all accidents were for men to be more careful, to avoid unsafe positions or to follow codes of practice. This, together with other remedies relating to the use of more experienced labour, improved supervision, etc., supports the assessment of accident causes made by colliery Safety Staff who considered that lack of reasonable care by someone, or unsafe methods or actions played a part in over a third of the accidents reported to SEL. Interim findings from the survey have already been presented by Inspectorate and SEL personnel to Safety Committees at the collieries involved with a view to stimulating remedial action. Some of the specific suggestions to reduce accidents, made at the meetings, were to raise and maintain the track standards of supplies haulage systems to those of manriding systems; to provide more training and close personal supervision for newly recruited haulage workers;
317
to keep the work place clean and tidy, particularly the 200 m of the mine roadway adjacent to coal faces; to improve the planning of new units and procedures by paying more attention to safety features and by involving representatives of the men who would be affected; and to hold more group discussions among the work-force on safety matters. The full findings from this survey are to be published (Nussey and Thompson, 1980). CONCLUSIONS
The work has made clear the following points: (1) British miners are prepared to participate in an interviewing system of the type described here provided that they are satisfied that there will be no unpleasant repercussions for them. (2) Most Safety Staff can organise a system of interviewing and can run it successfully for quite prolonged periods. (3) In the British coal mining industry, at least, such an interviewing system can provide much more detailed information about accidents leading to minor injury than is available from standard sources and is of use in furthering the understanding of the factors associated with such accidents. (4) Given management support, the information can be used to initiate remedial action or start investigations into particular problem areas. ACKNOWLEDGEMENT
The author wishes to thank the many members of NCB, Unions, the Mines Inspectorate and SEL who have co-operated and contributed advice and direct effort to the surveys. In particular he would like to acknowledge the support and encouragement given by the late C.R. Senneck during the greater part of this work. 0 Crown copyright reserved. REFERENCES Friedman, E., 1975. The Coal Board’s accident statistics, Paper E4, Proceedings of e Symposium on the Collection Analysis and Interpretation of Accident Data, Sheffield, 9-12 July, 1973. Health and Safety Commission, 1979. Consultative Document: Proposals for Notification of Accidents, Dangerous Occurrences, and Ill Health Regulations and Guidance Notes, HMSO, London. Health and Safety Executive, 1976a. Health and Safety: Mines and Quarries 1975. HMSO, London. Health and Safety Executive, 1976b. Health and Safety Research 1975. HMSO, London. Health and Safety Executive, 1978a. Health and Safety Research 1977. HMSO, London. Health and Safety Executive, 1978b. Health and Safety: Mines and Quarries 1977. HMSO, London. Nussey, C. and Thompson, H., to be published.
318 Price, N.H., Bye, C. and Niblett, B., 1974. One-line searching of Council of Europe conventions and agreements: A study in bilingual document retrieval. Inf. Storage Retr., 10: 145-154. Proctor, T.D., 1974. Progress report on the operation of the SMRE questionnaire machine at a small colliery. SMRE Technical Paper Pll. Proctor, T.D., 1977. A questionnaire machine for collecting accident data. J. Occup. Accidents, 1: 113-l 22. Proctor, T.D. and Cutts, N.J., 1976. A novel method of collecting information. Occup. Health, 28: 302-307. Robens, Lord, 1972. Report of the Committee on Safety and Health at Work, HMSO Cmnd 5034. HMSO, London. Safety in Mines Research Establishment, 1972. Safety in Mines Research 1971: Fiftieth Annual Report 1972. HMSO, London. Senneck, C.R., 1975a. Over-3-day absences and safety. Appl. Ergonomics, 6(3): 147153. Senneck, C.R., 197513. Experimental use of a paper questionnaire. Paper C5, Proceedings of a Symposium on the Collection, Analysis and Interpretation of Accident Data, Sheffield, 9-12 July 1973. Senneck, CR. and Nussey, C., 1973. Experience in NCB Doncaster Area with boots fitted with tungsten-carbide tipped studs. SMRE Technical Paper P4. Tregelles, P.G. and Senneck, C.R., 1973. A new approach to accident investigation in the Doncaster Area: An interim report. Mining Engineer, 150 (March): 291-327. Woodward, R.H. and Goldsmith, P.L., 1964. Cumulative Sum Techniques. ICI Monograph No. 3. Oliver and Boyd, Edinburgh.
319 APPENDIX
NCBISMRE
HAULAGE AND HANDLING
ANSWER
85
SHEET
86
Tsme 01accide”,
1
: PART 1 (SAFETY
ACCIDENT
OFFICER
SURVEY
-FROM
ARI)
Job 0”da” PART 2 (INTERVIEWER)
12
I-12 19
20
23,
24,
27
26
AlrI A,,
AlI\
,“,,,a15
I-12
PART 3 (SAFETY
Oale SMRE
OFFICER)
A,ii”l A2[25,
26,
Sayrhat
Flee
say “hat
Coded
say *a,
Punched
A2rl SMRE
USE ONLY
USE ONLY
320
APPENDIX
2
the
To be completed by the Safety Officer after the interview, answers written on the answer sheet.
Al.
PART 3
taking account of
What factors do you think probably helped to cause the accident? (Choose UP to three answers - one in each pair of boxes marked Al) Defective or signal
deslgned tools/equ ipment/suppl i&clothing/safety
or poorly
I ing device
I
__.~. __.....____..... ____..... ___..., _____ ~__ _____. _____ _._..___...._..._............._..... 0 1
Defective
or inadequately
Defective
or poorly designed
vehicles
Defective
or poorly
surroundings
installed
designed
rail track
..__ __......___......_.. .. ..
. .......~_.. 0
2
... ...._..... _....._......... . tti0
3
(clearances,
heat, water etc) .__ 16141
Failure to use available tooIsiequipmentlsuppties/ctothing/safety or signal Ling deviice __ ____.____. ___..___,.___._.._._... __._...__..... _____.._____________................................... 16151 Failure
of mechanical/electrical/safety
tnadequate
instruction/supervision
Inadequate
training
or signal .~~. .. .
t ing device
__~.....~~...
0 6 LLJ
.~ . ~~. .. ......._.................. _._._ . ...... .
_.________.____ ____.___________________ _.______..._.___..__..........................................
Lack of suitable tools/equipment/supplies/clothing/safety or signalllng ........................................................................................................................... device Lack of suitable
0
9
.........................................................................................
1
0
......................................................................................................
1
1
...........................................................
1
2
..........................................................
1 III
3
vehicles
Lack of experience Lack of reasonable
care by injured
person
Lack of reasonable
care by someone else
Misuse
of tools/equipment/supplies/clothing/safety
Misuse
of vehicles
Signal
device
......................................................................................................
misunderstood
Untidiness
or signalling
................................................................................................
q 1
4
1
5
1 m
6
1 7 .......................................................................... I
or poor housekeeping
Unsafe method of work not actively
discouraged by supervlsors ................................................................................................................
(egdeputies) Unsafe
action
by injured
person
Unsafe
action
by someone else
1
8
1
9
2
0
2 ccl
1
.............................................................................. ...............................................................................
...........................................................................................
B
Some other known
cause
No known cause
,___._____.____._.._............................................................... _.........._........._.
321 APPENDIX
2 cant
AZ. What do you think could be done to prevent
a similar accident happening again? (Choose up to three answers - one in each pair of boxes marked A2. appropriajezritten clarification alongside the coded boxes).
Clean or tidy
up:
Provision
Water _.__._..__...__ _________._._.__ _____ __ _____ __. Mud _____.._.________._._......._.... __..._ _____ a... Coal ________. _.,_..._____ _.________.... _.___.__.__ Stone or dirt _._____ ___,______ _.____._ ____ ____. Tool(s) ____.___________.. ____________.___.. ____._ Usable material ______________. ___._ _______ Scrap ___..__. _____ __.___ ___.____....__... ____.___... Equipment Something
(incl else
Better maintenance/repairs
of:
__._....
Locker/Stang/Scotch __.____. ____._.__._____..__. .._.._..._._._.._.__....... _____ __.___._.._.__ _ Loadbinder tool ______ __._ _....___. __.... __. Hand tool/Power Lifting equipment . ..____ ___.._ _.________.____.__._.___ clothing _____._______._ . ... __.._ ._._ ____. Protective Vehicle/Haulage rope/Conveyor ..._._.. _______ ___.____ __ Signalling or safety device Equipment/mechanical aid __......_._._....... Something else - -say what ._.___ .___.._.. _...
on:
Make the surroundings:
cables/hoses)..
- say what --
Where
____._..___._____.____ _____. . ..-..._.-..-.. -.-_Rail track _ ______________________.._____._..~.Less noisy _________________.~...-....*.-..-..~---. Toot (include locker & stang) ___ Better I ighted _.._______.______._.__________I______ Lifting equipment . .._______ _..._____ ___... Hotter or cooler .._______&__________________.._..._~-------..Vehicles__...___ ___._______._.___... _. .._._..... Less dusty ___._._----. __._-......... Less humid _______.__.______.____ Haulage rope _.._._...___._____ _____ __._.. __.. ___.____..__ _..-_... _____.----.-.. . ..--.--------Mot-e humid ______ _... Conveyor/Bunker/Chutes _._____._._.__.___..-..--- __.-...---.--.More spacious Signalling or safety device ..._. _.. la id out _______ ._._.._____. . . . . . . . .._.... ..---.-Better Surface underfoot (incl steps) -.-_-..-_I-_.___=_W-‘. Something else say what Something else - say what _______... --
Use of available:
Less
Locker/Stang/Scotch ___ _.._ ___..__ _._. Loadbinder ._.....____________ ______ _.__ _._._.____ Hand tools/Power tools _.___ _____ _._. Lifting equipment _._..__________ _.______.. Protective clothing __._.__ __.__ _.._._.... Vehicle/Haulage rope/Conveyor Signalling or safety device _______ Equipment/mechanical aid ___.______ Something else - say what ._.______. --
____ ___._______ _______________ Getting off the shift Getting on/off rranrider or cage _______.. ___ .______.__ _. In carrying out the job _____.______ To finish job so another can start ____ To get the job moving again _....__._..._... To get to the baths ___.___ ____ ___.__ ____.____ _____., .____ ____ _.___________.__ ____. To get to the job ____..__ ______._ __.._____ .._._ To avoid a hazard _.__..._ Some other reason - -say what ___________.__
Better design/construction
Other remedies:
of:
Locker/Stang/Scotch __.__._ __._., Loadbinder ._____.___ __.___________._...__.. Hand tools/Power tools __.._ __.__ __.
Lifting equipment __..______._.____.__.. Protective clothing _____._______. ____. Vehicle/Haulage rope/Conveyor Signall ing or safety device ______ Equipment/mechanical aid __. Something else - say what __.... -Nothing
think
Please add a written it would help.
haste:
.. .._____._....._____~~..~~~~.... Better supervision __._ ___. Use more men on the job ______._______ Use more experienced men ___________________ Avoid awkward or unsafe positions ___ Make better use of hands or body ____ Follow recommended codes of practice Pay more attention to signals Do job at different time or place ______._. Something else could be done - -I_ say what
could he done
clarification
- 80
on the back
of the answer
sheet
if you
322
APPENDIX
3 I
PAGE
NCB/SMRE
HAULAGE
INJURED
AND HANDLING
ACCIDENT
PERSONk
1
SURVEY
BOOKLET
We all want to stop accidents!
You can help by arlswering
Your answers
will
and on no account
a few simple questions.
be treated will
in strict
confidence
they be used against
you
by your employer
The information will be used by scientists into the cause of accidents.
Please help by answering
as carefully
looking
as you can.
323
APPENDIX
4
The next three questions are particularly NOTE TO THE INTERVIEWER please write down all the points he mentions and avoid the temptation too much. Don’t put words into his mouth but, if necessary,
important; to abbreviate
ask him questions to clarify
or fill out his statement.
10.
“Turn
to page 10.”
,....
“What
activity
were
you engaged in when you had
your accident?” Get the t&asJ he was deployed Get his activity
to that shift
(not occupation)
Get him to name any tools, Get him to name anything
in space marked
10,
appliances,
etc. that he was using.
that he was working
naming the objects,
11. “Turn to page 11.” . . . . . “Please describe Please step by step what happened next. pa in your accident.” Find out and write
in the space marked
how the accident
started
on.
YET.
etc.
how your accident name anything
that
11:
next,
ending
with
hurt him
(naming everything, including defects of objects, environment etc. that played a part).
Do not write about his activity describing his accident.
12.
at length
unless
in space marked
12.
roadway,
it is essential
“What do you think could be done to prevent an accident
Write suggestions
started and played a
and
step by step what happened ---_ how he was hurt and w&
19’s gate conveyor
at the time.
00 NOT LET HIM DESCRIBE HIS ACCIDENT
Write answer
eg repairing
for
like yours happening again?”
Do not give him ideas.