CHAPTER ONE – INTRODUCTION



Statistical Analysis on Factors in Reducing Construction Site Accident Frequency Rate in Hong Kong

W F Poon

Labour Department, The Government of the Hong Kong Special Administrative Region

and

Gary C.H. Ma

Industrial Centre, Hong Kong Polytechnic University

and

Dr. John K.L. Ho

Department of Manufacturing Engineering and Engineering Management,

City University of Hong Kong

Abstract

A set of Factories & Industrial Undertaking (Safety Management) Regulations is going through the legislation process and will soon be introduced to Hong Kong. The new Regulations will require employers to implement 14 safety elements in a safety management system. This paper describes the investigation on the effectiveness of the 14 elements, if the elements are applied to reduce construction site accident rate in Hong Kong.

The investigation was carried out by two parts. The first part of the statistical analysis was utilised the independent sample t-test to evaluate the relationship between the means of accident frequency rate and the corresponding safety element. The second part of analysis applied the multiple linear regression models to examine the combined effect of the safety elements in reduce site accident frequency rate. The findings and the recommendations are drawn at the end of the paper.

Key words: safety legislation, statistical analysis, site accident frequency rate

Introduction

The number of construction related accidents in Hong Kong remained at a very high level. Although, the construction industry employed less than 8% of the total industrial workforce, it had consistently accounted for more than one third of all industrial accidents over the last ten years. The situation was unacceptable.

The Hong Kong government, at its 1995 consultation paper, suggested changing from the traditional enforcement approach to a safety management system approach in tackling workplace safety and health issues.

A 14-elements safety management system framework is proposed under the drafted Factories & Industrial Undertaking (Safety Management) Regulations. The 14 elements are:

1. A safety policy which states the commitment of the enterprise to safety and health at work

2. A structure to assure implementation of the commitment to safety and health at work

3. Training to equipment personnel with knowledge to work safely and without risk to health

4. In-house safety rules to provide instruction for achieving safety management objectives

5. A programme of inspection to identify hazardous conditions and for the rectification of any such conditions at regular intervals or as appropriate

6. A programme to identify hazardous exposure or the risk of such exposure to the workers and to provide suitable personal protective equipment as a last resort where engineering control methods are not feasible

7. Investigation of accidents or incidents to find out the cause of any accident or incident and to develop prompt arrangement to prevent recurrence

8. Emergency preparedness to develop, communicate and execute plans prescribing the effective management of emergency situations

9. Evaluation, selection and control of sub-contractors to ensure that sub-contractors are fully aware of their safety obligations and are in fact meeting them

10. Safety committees to identify, recommend and keep under review measures to improve the safety and health at work

11. Evaluation of job related hazards or potential hazards and development of safety procedures

12. Promotion, development and maintenance of safety and health awareness in a workplace

13. A programme for accident control and elimination of hazards before exposing workers to any adverse work environment

14. A programme to protect workers from occupational health and hazards

The 14 elements safety management system is new to Hong Kong construction industry. This research investigated the effectiveness of these 14 elements in reducing the site accident frequency rate through questionnaire survey.

Questionnaire Survey

Literature reviewed have indicated that factors affecting site accident frequency rate were:

• Company characteristics;

• Safety management process elements; and

• Human behavioural factor towards safety.

For the development of the questionnaire, emphasis was made only on the company characteristics and safety management process elements. Human behavioural factor that mainly reflecting personal altitude towards safety was excluded because of the irrelevant to the research objective. The survey questionnaire, embedded with 14 elements of the safety management system framework, was divided into two parts:

• The first part of the questionnaire was structured to collect background information of the construction companies. Information, such as types of construction companies, nature of work conducted, size of employees, workers’ turnover rate and percentage of subcontracting, would be collected.

• The second part of this questionnaire was devised to collect information about the methods used by the construction companies and their respective site accident rate.

200 construction companies listed in the Hong Kong Construction Association Ltd. were randomly selected for the questionnaire survey. 62 companies completed and returned the questionnaire. The result of the questionnaire survey was tabulated in Table 1.

Table 1: Results of questionnaire survey

| | |Average accident |

| | |frequency rate per 1000 |

| | |workers |

| | | |

|Survey questions |Response | |

|Small company size (20 or few employees) |9 |246.59 |

|Medium company size (21-99 employees) |25 |235.95 |

|Large company size (100 or more employees) |28 |90.07 |

|0 – 20 % of subcontracting work |13 |48.48 |

|21 – 40 of subcontracting work |11 |103.64 |

|41 – 60 of subcontracting work |9 |187.22 |

|61 – 80 of subcontracting work |19 |207.69 |

|81 –100 of subcontracting work |10 |323.87 |

|Front line management responsible and accountable for safety |20 |303.01 |

|Middle management responsible and accountable for safety |24 |155.21 |

|Top management responsible and accountable for safety |18 |47.49 |

|With company safety policy in place |54 |157.10 |

|Without company safety policy |8 |269.58 |

|No safety organisation |20 |299.10 |

|Having a safety organisation but without clear responsibility |23 |148.63 |

|Having a safety organisation with clear responsibility |19 |65.25 |

|No safety committee |16 |298.81 |

|Ad hoc committee after accident |25 |184.47 |

|With a standing safety committee |21 |59.38 |

|No safety audit will be conducted |33 |241.21 |

|Audit in every 6 months |22 |106.75 |

|Audit in every year |7 |47.40 |

|Without any emergency preparedness programme at all |35 |228.85 |

|With an emergency preparedness programme |27 |97.42 |

|Without any health assurance programme |55 |178.00 |

|With health assurance programme in place |7 |121.44 |

|Without accident investigation programme at all |29 |275.32 |

|With accident investigation programme in place |33 |80.48 |

|No job hazard analysis programme in place |54 |190.69 |

|Job hazard analysis involved with general checklist only |7 |47.32 |

|Job hazard analysis with a comprehensive programme |1 |11.56 |

|No safety orientation at all |28 |272.07 |

|Safety orientation with handouts only |20 |122.32 |

|Safety orientation with a comprehensive course |14 |41.13 |

|Without personal protection programme at all |47 |207.84 |

|With personal protection programme in place |15 |58.13 |

|Without any process control programme at all |57 |181.50 |

|With process control programme in place |5 |58.88 |

|No safety promotional programme at all |26 |270.57 |

|Safety promotional programme attended by the line management |27 |120.20 |

|Safety promotional programme attended by the top management |9 |39.98 |

|Without any accident reporting programme |3 |383.94 |

|With accident reporting programme in place |59 |160.82 |

|Without any selection of subcontractors programme |61 |172.96 |

|With selection of subcontractors programme in place |1 |89.37 |

|Without any in-house safety rules |39 |201.29 |

|With in-house safety rules |23 |121.30 |

Table 1: Summary of survey results (continue)

| | |Average accident |

| | |frequency rate per 1000 |

| | |workers |

| | | |

|Survey questions |Response | |

|General inspection programme without any report and follow-up action |24 |273.93 |

|Goal setting inspection programme without any report and follow-up action |3 |131.74 |

|General inspection programme with report and follow-up action |19 |155.59 |

|Goal setting inspection programme with report and follow-up action |16 |44.65 |

|No safety training at all |26 |277.75 |

|Safety training for some supervisors |9 |164.53 |

|Safety training for all supervisors |5 |126.44 |

|Regular safety training to all members of the project team |11 |81.91 |

|Special training provided in addition to regular training |11 |36.78 |

These data were taken for statistical analysis to identify the essential elements that would contribute to the reduction of the accident frequency rate.

Statistical Analysis Methods

The selections of statistical analysis methods were based on the nature of the collected data and the expected outcomes of the analysed result.

Independent Sample t-test

Due to the nature of the collected data, independent sample t-test was adopted because of its capabilities to analyse the ordinal data (i.e. the data have a rank or order all categories according to some criterions). Independent sample t-test examines the significance in difference in the means of dependent variable for independent variables.

Multiple Linear Regression Model

Multiple linear regression model evaluates the combined effect of a set of independent variables in affecting the dependent variable. The concept of multiple linear regression analysis is identical to that of a simple regression analysis except that two or more independent variables are used simultaneous to explain the dependent variable. The regression model is in the following form:

AFR = Constant + B1X1 + B2X2 + …+ BnXn (Equation 1)

Where Bn is the partial regression coefficient for Xn; and Xn is the independent variables determine the outcome of the dependent variables.

Stepwise Regression

Due to the practical difficulty to describe numerous variables to include into the regression model, stepwise regression techniques are used to remove the insignificant variables. The technique of the stepwise regression is capable to look into different combinations of independent variables in affecting the dependent variable. The selection criteria are based on the partial regression coefficients, the coefficients of R2 and the value of the Adjusted R2. The value of the adjusted R2 is the percentage of variation of the dependent variable that can be explained by these significant independent variables.

The computer software “SPSS” was adopted to solve the complicated equations.

Results of the Statistical Analysis

The first part of the statistical analysis involved the independent sample t-test, which was used to compute the relationship between the means of accident frequency rate and the corresponding safety elements implemented. A 95% confidence level was set as the criteria for the analysis. It meant that if the calculated P-value was less than 0.05, then the difference between groups under tested was statistically significant. For the safety element with its entire test groups were found to have P-value less than 0.05, then the element was found significantly correlation with the accident frequency rate rate.

The test results and remarks on the elements' significance with the accident frequency rate were summarised in Table 2.

Table 2: Summary of Independent T-test result

| |Significance in the | |Means of accident |Correlation with |

| |Lavene’s test for the | |frequency rate |accident frequency |

| |equality of variance |P-value | |rate |

|Tested Item | | | | |

|Company size: | | | |Insignificant |

|small Vs medium |0.330 |0.784 |Not different | |

|medium Vs large |0.185 |0.000 |Different | |

|large Vs small |0.073 |0.000 |Different | |

|Subcontracting work: | | | |Insignificant |

|0% - 20% Vs 21% - 40% |0.111 |0.002 |Different | |

|21% - 40% Vs 41% - 60% |0.132 |0.005 |Different | |

|41% - 60% Vs 61% - 80% |0.585 |0.552 |Not different | |

|61% - 80% Vs 81% - 100% |0.753 |0.003 |Different | |

|81% - 100% Vs 0% to 20% |0.007 |0.000 |Different | |

|Management involvement: | | | |Significant |

|front line management Vs middle management |0.06 |0.000 |Different | |

|middle management Vs top management | | | | |

|top management Vs front line management |0.004 |0.000 |Different | |

| |0.000 |0.000 |Different | |

|Safety policy: | | | |Significant |

|safety policy Vs no safety policy |0.039 |0.001 |Different | |

|Safety organisation: | | | |Significant |

|without clear allocation of responsibility Vs without any |0.074 |0.000 |Different | |

|safety organisation at all. | | | | |

|responsibility clearly defined Vs responsibility was not |0.511 |0.000 |Different | |

|defined. | | | | |

|responsibility clearly defined Vs without any safety |0.028 |0.000 |Different | |

|organisation at all. | | | | |

|Safety Committee | | | |Significant |

|ad hoc safety committee after accident Vs no safety |0.729 |0.000 |Different | |

|committee | | | | |

|ad hoc safety committee after accident Vs permanent safety |0.002 |0.000 |Different | |

|committee | | | | |

|permanent safety committee Vs no safety committee |0.001 |0.000 |Different | |

Table 2: Summary of Independent T-test result (continue)

| |Significance in the | |Means of accident |Correlation with |

| |Lavene’s test for the | |frequency rate |accident frequency |

| |equality of variance |P-value | |rate |

|Tested Item | | | | |

|Safety audit: | | | |Significant |

|safety audit every year Vs no safety audit |0.012 |0.000 |Different | |

|safety audit every year Vs safety audit every six months | | | | |

| |0.247 |0.025 |Different | |

|Emergency preparedness programme: | | | |Significant |

|emergency preparedness Vs no emergency preparedness |0.035 |0.000 |Different | |

|Health assurance programme: | | | |Insignificant |

|health assurance Vs no health assurance |0.398 |0.224 |Not different | |

|Accident investigation programme: | | | |Significant |

|accident investigation Vs no accident investigation |0.003 |0.000 |Different | |

|Job hazard analysis: | | | |Insignificant |

|job hazard analysis with general checklist Vs no job hazard|0.001 |0.000 |Different | |

|analysis | | | | |

|job hazard analysis with general checklist Vs comprehensive| | | | |

|job hazard analysis programme | |0.035 |Different | |

|comprehensive job hazard analysis programme Vs no job | | | | |

|hazard analysis | | | | |

| | |0.116 |Not different | |

|Safety orientation programme: | | | |Significant |

|safety orientation (with handout only) Vs no safety |0.005 |0.000 |Different | |

|orientation | | | | |

|safety orientation (with handout only) Vs safety |0.022 |0.000 |Different | |

|orientation (comprehensive course) | | | | |

|safety orientation programme (comprehensive course) Vs no | | | | |

|safety orientation |0.001 |0.000 |Different | |

|Personal protection programme: | | | |Insignificant |

|personal protection Vs no personal protection |0.000 |0.000 |Not different | |

|Process control programme: | | | |Significant |

|process control Vs no process control |0.006 |0.000 |Different | |

|Safety promotional programme: | | | |Significant |

|safety promotion attended by line management Vs no safety |0.173 |0.000 |Different | |

|promotion | | | | |

|safety promotion attended by the line management Vs safety |0.017 |0.000 |Different | |

|promotion attended by top management | | | | |

|safety promotional attended by top management Vs no safety | | | | |

|promotion |0.001 |0.000 |Different | |

|Accident reporting programme: | | | |Significant |

|accident reporting Vs no accident reporting |0.097 |0.001 |Different | |

|Selection of subcontractors programme: | | | |Insignificant |

|selection of subcontractors Vs no selection of | |0.476 |Not different | |

|subcontractors | | | | |

|In-house safety rules: | | | |Significant |

|in-house safety rules Vs no in-house safety rules |0.182 |0.007 |Different | |

Table 2: Summary of Independent T-test result (continue)

| |Significance in the | |Means of accident |Correlation with |

| |Lavene’s test for the | |frequency rate |accident frequency |

| |equality of variance |P-value | |rate |

|Tested Item | | | | |

|Safety inspection: | | | |Insignificant |

|general inspection with no report and no follow up Vs goal |0.074 |0.009 |Different | |

|setting inspection with no report and no follow up | | | | |

|general inspection with report and follow up action taken | | | | |

|Vs goal setting inspection with no report and no follow up |0.151 |0.619 |Not different | |

|general inspection with report and follow up action taken | | | | |

|Vs goal setting inspection with report and follow up taken | | | | |

|general inspection with no report and no follow up action |0.002 |0.000 |Different | |

|taken Vs goal setting inspection with report and follow up | | | | |

|taken | | | | |

| |0.000 |0.000 |Different | |

|Safety training programme: | | | |Insignificant |

|safety training for some supervisors Vs no safety training |0.688 |0.001 |Different | |

|safety training for some supervisors Vs safety training for| | | | |

|all supervisors |0.152 |0.316 |Not different | |

|safety training for all supervisors Vs safety training for | | | | |

|the whole project team |0.419 |0.023 |Different | |

|regular safety training for the whole project team Vs | | | | |

|special training in addition to regular training |0.039 |0.002 |Different | |

|special training in addition to regular training Vs no | | | | |

|safety training. | | | | |

| |0.001 |0.000 |Different | |

The second part of the statistical analysis used the same questionnaire survey results to undergo another statistical analysis with the multiple linear regression models to evaluate the combined effect of the safety elements in reducing site accident frequency rate. Stepwise regression was firstly adopted to remove the insignificant variable.

After processing of the stepwise regression analysis, five elements, namely:

1) accident/incident investigation programme,

2) safety inspection programme (general inspection programme with report and follow up action taken),

3) accident/incident reporting programme,

4) safety orientation programme (with handout only) and

5) safety orientation programme (with comprehensive course),

were found to have the combined effects in reducing the site accident frequency rate (Table 3 referred). The R-value calculated for the combination of all these 5 elements was 0.923. Thus the adjusted R2-value was 0.84 with a standard error of the estimate equalled to 46.1328.

Table 3: Stepwise Regression to Entered/Removed Variables

|Model |Variables Entered |Stepwise Criteria |

|1 |Accident/Incident Investigation Programme |Probability-of-F-to-enter = 0.100 |

|2 |Safety Inspection Programme (General inspection programme with|Probability-of-F-to-enter = 0.100 |

|3 |Accident/Incident Reporting Programme |Probability-of-F-to-enter = 0.100 |

Table 3: Stepwise Regression to Entered/Removed Variables (Continue)

|Model |Variables Entered |Stepwise Criteria |

|4 |Safety Orientation Programme (with handout only) |Probability-of-F-to-enter = 0.100 |

|5 |Safety Orientation Programme (with comprehensive course) |Probability-of-F-to-enter = 0.100 |

These five elements were further undertaken the multiple linear regression analysis in respect of the accident frequency rate as the dependent variable. The coefficients calculated (see Table 4) were applied to Equation 1 and gave rise to a new formula:

Accident frequency rate = 383.943 – 81.342 A/IIP – 80.163 SINSPD3 – 112.379 A/IRP – 76.098 SORIEND1 – 74.652 SORIEND2

Table 4: Results of the Coefficients

| |Unstandardized |Standardized |Order of the |Collinearity Statistics |

|Model |Coefficients |Coefficients |contribution to | |

| | | |reduce AFR | |

| |Bn |Beta coefficient | |Tolerance |VIF |

| |(Partial regression coefficient) | | | | |

|(Constant) |383.943 | | | | |

|A/IIP | | | | | |

|SINSPD3 | | | | | |

|A/IRP | | | | | |

|SORIEND1 | | | | | |

|SORIEND2 | | | | | |

| |-81.342 |-0.355 |1 |0.215 |4.642 |

| |-80.163 |-0.307 |2 |0.237 |4.125 |

| |-112.379 |-0.211 |3 |0.933 |1.072 |

| |-76.098 |-0.311 |4 |0.267 |3.740 |

| |-74.652 |-0.273 |5 |0.249 |4.014 |

Where A/IIP denotes Accident/Incident Investigation Programme

SINSPD3 denotes Safety Inspection Programme (General inspection programme with report and follow up action taken)

A/IRP denotes Accident/Incident Reporting Programme

SORIEND1 denotes Safety Orientation Programme (with handout only)

SORIEND2 denotes Safety Orientation Programme (with comprehensive course)

Interpretation of the results

Independent sample t-test

The T-test results indicated that the elements had significant correlation with the site accident rate were:

1) safety policy,

2) safety organisation,

3) safety audit,

4) safety committee,

5) emergency preparedness,

6) in-house safety rule,

7) safety orientation,

8) safety promotional programme,

9) accident reporting programme,

10) accident investigation programme,

11) personal protection programme,

12) process control programme and

13) management involvement

Apart from the factor of "management involved on safety", the identified safety elements were also embraced in the drafted safety management framework.

Stepwise Regression

The adjusted R2 is 0.840 which means 84% of the variation of the accident frequency rate could be explained by the five process elements in the regression model.

Discussion

The independent sample t-test identified elements that have individual influence on the site accident rate. However, in the real environment safety elements are not isolated but are affecting each other. Thus the multiple linear regress model was used to identify the combination of safety element that would have most effects on the site accident rate. This argument was later proven correct as the safety inspection program that was excluded by the t-test came second on the most combined contribution factors list.

In the following context, explanations were given on how and why these 5 factors have significant relationship with the site accident frequency rate in the Hong Kong construction industry.

Relationship between accident/incident reporting & investigation programme and the site accident frequency rate

Accident/incident reporting & investigation programme was found to be the most significant contributor to reduce site accident frequency rate. It provides useful information to prevent similar accident in recurring. The information gathered from accident/incident investigations are also useful and effective mechanism to formulate the corrective actions. However, as the information could only be gathered after an accident had actually happened or had learned experience from others, it is only re-active indicator to reflect site safety performance.

Relationship between safety inspection programme and the site accident frequency rate

Safety inspection programme has been identified as the second most effective contributor on reduction of site accident frequency rate and this result is consistency with many previous research works. The advantage of safety inspection is to expose potential hazard in the work site before an accident happens, thus, it is regarded as a pro-active site safety performance indicator.

However, the effectiveness of safety inspection to combat site accident frequency rate is very much relying on the comprehensiveness of the inspection programme and the competency of the personnel carrying out the inspection. In this connection, consideration and emphasis have been made on the setting of questionnaire. According to the research finding, general safety inspection programme with report and follow up action is the most effective tool to reduce site accident rate.

Relationship between safety orientation programme with the site accident frequency rate

Safety orientation programme is particular important to those new workers working in a construction site.

Commissioner of Labour (1993) stated that new workers are the most vulnerable to site accidents. It is because new workers are not familiar with site environment and the potential hazard as well. Hence, there is a need to organise orientation for this high causality group. From the research finding, it is observed that the effect of safety orientation programme (with handout only) is better than the programme with comprehensive course. This indicates that no matter how comprehensive the programme is, it can only improve site accident frequency rate to a limited extent. As the majority of the new workers to a construction site are coming from low level of education group, it is difficult to break in with various information to their mind in a relatively short period of time. On the contrary, simple diagrams or pictures in showing the site working environment and potential hazard may be more impressive than any other comprehensive course in such a short duration of time.

In additional to the five significant factors, there are also several interesting observations from the returned survey questionnaires.

Relationship between management involvement in safety and the site accident frequency rate

The survey result indicates that management involvement in safety is significantly correlated with the site accident frequency rate. Furthermore, the average site accident frequency rate is exceptionally good when the top management is directly responsible and accountable for safety in the work site. This result is expected because top management commitment is the necessary condition for the success of any safety programme. According to much literature, it reveals that many accidents are the result of management failure. Hinze and Raboud (1988) found that all successful safety management programmes must be supported by top management. Hence, management commitment and support are essential to bring accident rates down.

Relationship between employees’ size of company and the site accident frequency rate

The survey shows that larger companies have generally better average site accident frequency rate than that of the smaller companies. Although, it cannot prove the significant correlation between them, it is generally believed that larger companies may have better capability of combating site accident frequency rate. Possibly, larger companies may have sufficient resources to implement more structured and formalised safety programmes in enhancing safety in the work sites.

Relationship between the level of subcontracting work and the site accident frequency rate.

According to the survey the average site accident frequency rate is directly related with the level of subcontracting work. Lai (1987) attributes the high site casualty rates to the use of labour-only subcontractors.

In Hong Kong the subcontracted labour is highly mobile. This high mobility of subcontracted labour, makes the worker less familiar with the site environment and the potential hazard, is a constituting factor to the high accident rate. Furthermore, due to the financial incapability, many small subcontractors are unable to implement comprehensive safety programmes. As such, it is hard to uphold their safety awareness. Besides, the subcontracted labour is rewarded according to the number of pieces of work that have been completed, therefore, the workers often make light of safe working practices in the pursuit of productivity.

In addition, due to the deficiency of the existing safety regulations, the principle contractor is held liable under the majority of the existing construction sites safety regulations. This is reflected by the number of prosecution made to subcontracted labour is relatively much smaller than the one to the principle contractor. This information has given a wrong message to the subcontracted group that site safety is not their responsibility. As such, this subcontracted labour may make light their legal liability and not co-operated with the principle contractors. This is the reason why this subcontracted labour is difficult to be controlled and hence constituted for the high casualty rate in the Hong Kong construction industry.

Conclusion

The new safety management regulation is an effective tool to reduce the site accident rate in the construction industry. This paper has statistically proved that 12 out the 14 elements of the proposed safety management system framework were effective tool to reduce the site accident frequency rate.

The research further identifies accident reporting programme is the third contributor in reducing accident rate, but this element has not been included in the proposed safety management system framework. It is recommended that the government to consider this element in the final version of the safety management system.

Since not all the safety process elements stipulated in the new regulations have significant correlation with reduction of accident frequency rate, the government is urged to enforce the new safety management regulation in stages so that it will not become a heavy burden to the industry.

References

Hinze, J.,and Raboud, P.,(1988) Safety on large building construction projects, Journal of Construction Engineering and Management, ASCE, 114(2), pp.286-293.

Hong Kong Government (1993) Commissioner for Labour Annual Report, Government Printer, Hong Kong.

Labour Department (1999) A Guide to Safety Management, Hong Kong

LAI Man-yi (1987) A Review of the Subcontracting Systems in the Hong Kong Construction Industry, MSc thesis, The University of Hong Kong, Hong Kong.

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