Photo: Studies have found that 

roof bolting is the most dangerous 

job in underground coal mines.

the injury and the mechanism by 

which the injury occurred.

Analysis of injury narratives 

has previously been undertaken in 

underground mining. Helander and 

Krohn (1983) conducted an analysis 

of injury narratives for most hazardous underground machinery in 

hard-rock mining. They coded the 

narratives for worker activity, suggested cause of accident machine 

part involved and body part injured. 

Similarly, Helander, Krohn and Curtin (1983) coded the injury narratives 

from 600 roof bolter accident reports 

for cause, machine part and body 

part injured. It was concluded that 

roofbolting was the most dangerous 
job in underground coal mines and that rock falls accounted 

for 25 percent of roof bolting injuries. 

The additional information available in injury narratives has the potential to aid in prioritizing effective control 

measures. The purpose of this investigation is to use injury 

narratives to identify opportunities for reducing common 

injury risks associated with underground coal mining equipment. It also discusses potential risk control strategies.

Risk is understood to be a combination of the 

probability of exposure to a hazard and the potential 

consequences of that exposure. Risk reduction can 

occur through reducing the probability of the hazard 

occuring, (although this typically requires the elimination or substitution of the hazard) or by reducing 

the severity of the potential consequences through 

design or administrative controls.

Narrative example Codes

Drill steel became lodged in top, employee attempted to Bolter: drilling: caught 

put wrench on drill steel and slipped hitting up lever catching between.

index and middle fingers on right hand between wrench and 

drill steel. (Required 11 stitches).

EE was installing outside bolts next to ribline. While in drilling Bolter: drilling: struck 

procedure, a piece of top (15.24 mm (6 in.) thick, 91 mm (36 in.) by: falling rock.

long 79 mm (31 in.) wide struck backside, pushing ee into bolter

boom, injuries included contusions to back, nose (fractured) and 

mouth. Bolter: drilling: struck by: falling rock.

Injured was moving c.m. cable out of roadway. He was standing Continuous miner:

bent over reaching to his left and pulling to his right when he felt handling cable: strained 

and heard a pop in his back. EE stated he lay there for 

approx. 5 min before was able to get up. Stated he was 

still having excruciating pain.

The repairman was positioned about 7 m (20 ft) in front of the Continuous miner:

machine & instructed the miner operator to stop because the standing near: 

curtain was caught on the ripper ring. Machine operator heard caught between.

repairman say OK & assumed he was clear of the machine. 

He started tramming backwards & repairman was caught 

between rib & left ripper ring.

Employee was operating a scoop when he ran over obstruction Scoop/LHD: driving: 

in roadway and struck head on canopy of scoop. rough road.

EE was crushed between a coal rib and a rock duster being Scoop/LHD: standing pulled by scoop.

 near: caught between.

EE was operating a shuttle car and had just received a load of Shuttle car: driving:

coal from continuous miner. He trammed from face & made the ran into.

turn to go west to the feeder. Operator of second Shuttle car 

waited for EE to clear the intersection. 1st car had to back up a 

short distance to clear the left rib. Operator of 2nd car thought 

he had cleared the intersection & pulled forward striking 1st car.

Employee was operating shuttle car when rock flew up and hit Shuttle car: driving: 

him in the mouth causing a laceration to his lip and a chipped struck by.

tooth.

This is a “low coal” operation. As the injured exited the shuttle Shuttle car: egress:

car in a rolling motion of his body, he heard and felt something strained.

snap in his knee.

Employee was in a Mantrip when it hit a pothole causing Personnel transport:

employee to be thrown from his seat onto the floor on the mantrip, traveling; rough road.

injuring his back. 

Table 1

Examples of injury narratives and coding.
Method

Background data , and the narrative text field for all

injuries (N=3405) reported to MSHA (as required under

CFR 30, Part 50) as occurring at U.S. underground coa l

mines in 2004 were obtained from www.cdc.gov/niosh!

mining/data. Reportable injuries, as defined by MSHA,

includes accidents that require medical trea tment, loss

o f consciousness, tempo rary restrictions in work duties

or lost time but excludes "first aid only" injuries. These

data include mine employees and independent contractors working on the mine site.

As part of each injury report, mines are required

to provide a narra tive describing each incident wh ile

detailed informa tion is required by the regulation. In

reality, though,the narratives reported vary in the detail

provided,and rarely approach that stipulated.Analysisof

the narratives involved the first investigator reading the

full text field for each injury and coding for the activity

being undertaken at the time ofthe injury, and the causal

mechanism (Table 1).

The coding categories were not pre-structured but,

rather,evolved during the data analysis in a method similar to Glaser and Strauss's (1967) constant comparative

coding. In this method of analyzing qualitative data , the

ana lyst initially codes each incident into as many ca tegories as possible.The coding categories used are developed

throughout the analysis.The general strategy during coding is to compare each case with previous incidents in

the category to determine the category boundaries and

relationships between categories, hence "constant comparative." Frequencies of the cross-tabulated combinations of codes were calcula ted and presented graphically

to aid interpretation.

The analysis is not an o bjective, mechanistic process,

but one that draws on the researcher's developing understanding of the phenomenon of interest. The coding

process is about conceptualizing, reducing and re lating

the data obtained in qualitative form. The "grounded

theory," which results from such analysis offers insight,

e nhances underst anding and offers mea ningful opportunitiesfor action.The advantage of this technique over the

use of pre-structured standard coding protocols is that

it allows context sensitive categories to be used. This, in

turn, assists in the identification ofspecific opportunities

for action. It also allows the possibility of identifying

previously unrecognized categories.

Results

In 2004, there were 646 underground coal mines in the

U.S. These mines employed 37,445 miners and reported

3,405 injuries to MSHA. Of these injuries, 17 percent

were associated with bolting machines (593 injuries),

8 pe rcent with continuous miners (283 injuries) and 4

percent each with scooplLHD (151 injuries),shuttle cars

(134 injuries) and personnel transport (145 injuries).Figures 1 through 3 present the breakdown of these 1,306 injuries by equipment, activity being undertaken at the time

of the injury and mechanism of injury. Seventy percent

of the reported injuries involved lost

time, while the remaining 30 percent

involved periods of restricted duties or

medical expenses only.

The most common injury mechanism associated with bo lting machines

is rock falling from su pported roof

(roof that has been bolted ).This caused

208 bolting machine injuries in 2004

(33 percent of injuries associated with

bolting machines). This type of event

also accounted for 59 injuries associated with the operation of continuous

miners in 2004 (21 percent of injuries

associated with continuous miner operation). An inspection of all injury

narratives suggests th at 13 percent of

all injuries reported in 2004were caused

by rock or coal falling from supported

roof (477 injuries).

Injuries involving a part of the body

being struck by, or caught between,

during adj usti ng, drilling or bolting,

occurred with relatively high frequency.

Relatively minor injuries occurring as a

consequence of being struck by falling

drill steels, bolts or plates accounted for

many of the "struck by"cases. More serious injuries occurred were associa ted

with unintended consequences of the

operation of bolting controls causing

operators or another person to be struck

by a moving part of the bolting machine,

caught betwee n the bolting machine

and the rib, or caught in pinch points
on the machine. The control Unintended consequences of the operation of bolting controls is a common

operation was sometimes un- cause of injury in underground mines.

intentional, typically caused ~G:;~::~~::~~~~:L~ by bumping a control with a

self-rescuer or battery, or a

control being struck by a falling object. Injuries caused by

intentional control operation

may be further divided into

cases where:

• The wrong control was

operated.

• The correct control was

operated in the wrong

direction.

• Operating of the intended

control in the intended

direction while the injured

employee (either the operatoror another person)

was in a position of danger

(Table 2).

Strains associated with

bolting and handling of bolting supplies (drill steels, bolts,

plates and resin) also occurred

relatively frequently. The most

frequent injuries associated
with continuous miners are strains while handling cable. 

Handling cable accounted for 27 percent of the 283 continuous miner related injuries (76 injuries). 

Taken as a group, the most common injuries associated with LHD/scoop, shuttle car and personnel transport 

were collisions while driving or traveling (64 injuries), 

driving or traveling over a pothole or other road abnormality (85 injuries) and being struck by an object while 

driving or traveling (106 injuries). These latter injuries 

have diverse origins, including being struck by falling 

Table 2

Examples of control operation hazards.

Unintentional control operation (guarding)

• EE had just swung the drill head on the fletcher RRII roof bolter to 

drill hole for sister hook when his SCSR (Self-contained self-rescuer) 

hit the swing lever thus pinching his knee to the coal rib from the drill 

head of the bolter.

• While putting drill steel together in the process of drilling a test 

hole, a piece of rock fell striking the control lever causing drill pot to 

rise pushing drill steel into his left hand.

• As EE was installing a cable bolt he accidentally hit the control 

levers with a bolt causing the drill head to swing out against his left 

foot, causing a fracture.

Incorrect control (control layout, coding)

• The employee was roof bolting when he went to drop the mast and 

pulled the wrong lever. He set the jaws on his right hand causing a 

smashing injury to that hand.

• EE stated he was trying to unplug the head on the roof bolter. He 

placed his hand on the slide and his coworker was to activate the 

rotation lever but hit the wrong lever and dropped the head, catching 

EE’s hand.

• While he was being trained on the roof bolter, he caught his right 

middle finger in the jaws. He then pulled the wrong lever, tightening 

it against his finger. He fractured the bone at the tip of his finger. 

Incorrect direction (direction compatibility)

• Employee was bringing steel out of hole. As he was separating the 

steel he reached over to lower the head to give more room to get the 

steel out. When he engaged the head he went the wrong way, catching his finger between the two pieces of steel, causing a laceration as 

well as a broken bone. 

• Injured party had just put up his 1st bolt in the entry. When he 

started to swing the boom, he pulled the lever the wrong way, striking his right knee.

Operation while person in position of danger (guarding, interlock)

• After finishing bolting a cut, employee was attempting to hand 

reflectors in the roof bolt plate. Due to high top, he stepped up on the 

roof drill at the scissor jack of the ATRS so he could reach the top. 

As he stepped onto the frame, the other bolter operator began dropping the ATRS to prepare to move the machine. Employee’s foot was 

caught in a pinch point resulting in a fracture.

• The EE was watching the bolter operator bolt and upon leaving put 

his hand on the arms that attached to the head. At the same time the 

bolter operator raised the head, thus crushing the left pinkie finger of 

the EE. 

material from a roof, wall or thrown up from the floor, 

as well as striking objects hanging from the roof. 

Discussion

These results are consistent with previous observations (Sanders and Shaw, 1989; Helander et al., 1983) that 

roof bolting machines are the equipment most frequently 

involved in underground mining injuries (17 percent), 

and being that struck by rock falling from supported 

roof as the most common mechanism. The proportion 

of injuries associated with bolting machines 

in U.S. underground coal mines appears to 

have remained unchanged since the 1970s 

(15 percent, Jamison, 1977; 17 percent, 

Sanders and Shaw, 1989; 16 percent, Klishis 

et al.,1993). 

Similarly, the proportion of injuries associated with continuous miners (8 percent) 

is consistent with that previously reported 

for U.S. mines (7 percent, Sanders and 

Shaw,1989). The total proportion of injuries 

associated with the equipment considered 

(37 percent) is considerably higher than 

that reported recently for underground coal 

mines in New South Wales, Australia (23 percent, Burgess-Limerick and Steiner, 2006). 

The differences may be a consequence of 

different environmental conditions (higher 

roof heights in Australian mines) and differences in mining methods (in Australia, 

bolting is predominantly undertaken from 

integrated bolter-miners). Perhaps in part 

as a consequence of the higher roof heights, 

Australian mines have a higher prevalence 

of the use of screening to prevent minor rock 

fall injuries. 

The use of the frequency of reported 

injuries for the prioritization of risk control 

strategies has limitations because of the 

tendency to underestimate the importance of 

relatively rare, but high consequence events. 

Injury reports also underestimate the contribution of risk factors such as whole body 

vibration that have a long-term cumulative 

contribution to an elevated risk of injury. 

However, taking these limitations into consideration, the results of the injury narrative 

analysis suggests the following hazards as the 

highest priority for elimination or control:

• Rock falling from supported roof.

• Inadvertent or incorrect operation of 

bolting controls.

• Handling continuous miner cable.

• Collisions while driving LHD/scoop, 

shuttle cars and transport.

• Rough road while driving or traveling 

in LHD/scoop, shuttle cars and transport.

Rock falling from supported roof

Rock fall data are remarkably consistent 

with previous reports. For example, Klishis, 

et al. (1993) analyzed 2,685 bolting related 

injury narratives and found that 911 (34 per-
of this type (Robertson and Hinshaw, 2002). Indeed, 

injuries due to rock falling from supported roof were 

almost non-existent in a similar analysis of equipment 

related injury narratives from Australian underground 

coal mines where screens are routinely put in place during bolting (Burgess-Limerick and Steiner, 2006). 

The importance of preventing rock fall injuries 

cannot be overstated. Where low seam heights make 

screening with steel mesh difficult, it may be necessary 

to develop alternative means of reducing the risk of 

minor rock falls such as the use of shotcrete or other 

membrane (Pappas et al., 2002). Preventing minor rock 

falls, whether through screening or other means, could 

prevent nearly 500 injuries per year or 13 percent of all 

injuries in U.S. underground coal mines. 

However, it may take more than 

technological advances to achieve 

control of this risk. As Mark (2002) 

noted in the context of roof bolting, 

improved technology must be accompanied by changes in the perceptions regarding acceptable risks. A 

tendency to accept current risk levels 

and rely on administrative controls 

was evident from many of the injury 

narratives. For example, the following 

is typical:

“Employee was operating a continuous miner in unit 1. He was standing just outby the continuous miner 

tail and a piece of roof rock fell from 

between the roof bolts, striking his 

back. The incident caused a contusion 

to the back and a fracture to a rib. The 

employee will be instructed to always 

check the roof and rib in his work are 

and to scale down loose material.” 

The narrative betrays an underlying assumption that the injury was 

cent) involved falls of roof material (cf. 33 percent this 

report). Similarly, Bise, et al. (1993) determined that in 

1987, 57 of 319 continuous miner related injuries (18 

percent) were due to falling rock (cf. 21 percent, this 

report). 

The total number of injuries as a consequence of 

coal or rock falling from supported roof (477) is reduced 

from the 650 reported by Robertson, et al. (2003) as the 

annual average from 1995 to 2001. This suggests that 

there has been a reduction in overall injuries of this type 

in recent years. While this reduction reflects the overall 

reduction in injury rate occurring during this period, it 

is likely that the change is, in part, a consequence of the 

introduction of roof screening in some U.S. mines. This 

has been demonstrated to virtually eliminate injuries 

FIGURE 2

Injuries associated with continuous mining machines in 

U.S. underground coal mines in 2004 (283) coded for activity 

and mechanism of injury event. Line width indicates number of injuries reported.

Increased length of cables might be a contributing factor in some injuries 

associated with cable handling in underground coal mines.

FIGURE 1

Injuries associated with bolting machines in U.S. underground coal mines in 2004 (593) coded for activity and mechanism of injury event. Line width indicates number of injuries 

reported.
due to the employee’s failure to check the roof and 

remove loose material, that is, that the employee’s 

behavior is the source of the hazard, rather than the 

employer’s failure to provide a safe system of work. This 

is a cultural issue that requires change before meaningful reductions in injury risk will be achieved.

Inadvertent or incorrect operation 

of bolting controls

The hazards associated with inadvertent operation 

of controls, operation of incorrect controls, operating 

controls in an incorrect direction, or while a person is 

located in a pinch point, have long been recognized. 

Miller and McLellan (1973) commented on the “obvious need” to redesign roof bolting machines. They 

suggested that, of 759 bolting machine related injuries, 

72 involved operating the wrong control Helander et 

al. (1983) determined that 5 percent of bolting machine 

accidents were caused by control activation errors. Improvements to guarding to prevent accidental control 

operation, standardization of mining equipment controls, especially drilling and bolting controls, and the 

use of shape and length coding has been suggested on 

numerous occasions during the past 40 years. (Helander 

et al., 1983; Klishis et al., 1993; Hedling and Folley, 1972; 

Grayson et al., 1992; Helander et al., 1980; Muldoon et 

al., 1980). 

Hedling and Folley noted (in the context of continuous miner controls) that “the widespread use of 

traditional round control knobs, regardless of function being controlled, is another source of error in 

operation.” They proposed that “each control knob is 

designed to resemble (at least symbolically) the equipment it represents.” Similarly, Helander et al., (1980) 

suggested that “poor human factors principles in the 

design and placement of controls and inappropriately 

designed workstations contribute to a large percentage of the reported injuries.” In particular, a lack of 

standardization of controls was noted, with more than 

25 different control sequences being identified, differences existing even on similar machines produced by 

same manufacturer. Helander et al., also noted the lack 

of control coding, violation of direction stereotypes, a 

mixture mirror image and left/right arrangements and 

the possibility of inadvertent operation. 

Helander and Elliott authored a proposal in 1982 

for a Society of Automotive Engineers standard titled 

“Human Factors Guidelines for Roof Drills,” which 

addressed these issues. The proposed standard was 

later subsumed within a later proposed standard titled 

Human Factors Design Guidelines for Mobile Underground Mining Equipment that was defeated at a 

ballot in 1984. Klishis et al., (1993) again noted a lack 

of standardization of bolting machine controls, even 

among machines from the same manufacturer and commented on the potential for injuries due to incorrect 

control operation. 

Bolting machine controls require standardization 

to an appropriate layout (including shape and length 

coding) to reduce the probability of operation of the 

wrong control, although open questions remain regarding whether control layouts should be mirrored, and 

the relative importance of shape, location and length 

coding for the prevention of “wrong control” type erFIGURE 3

Injuries associate with load-haul-dump/scoop (151), shuttle 

car (134), and personnel transport (145) in U.S. underground 

coal mines in 2004 coded for activity and mechanism of injury 

event. Line width indicates number of injuries reported.

rors. Control standardization must also consider the 

question of directional control-response compatibility 

principles to reduce the probability of operation of 

controls in the wrong direction. Further research is 

required to determine the most appropriate layout 

and directional control-response relationships specific 

to bolting machines. Chan et al., (1985) suggested that 

“conflicting recommendations and gaps in the literature 

would need to be resolved before any standardization 

of control-response relationships for mining machines 

was possible.” This remains true.

Cable handling

Analysis of the injury narratives suggest that, in 2004, 

handling cable accounted for 76 of the 283 continuous 

miner related injuries (27 percent). That was more than 

the 11 percent noted previously (Bise et al., 1993), but 

consistent with recent Australian data in which 23 percent of continuous miner related injuries were associated with handling cable (Burgess-Limerick and Steiner, 

2006). Technological changes during the last 10 years 

have resulted in longer cuts. It may be speculated that 

increases in the length of cable being handled, combined 

with reduction in the number of miners and increases in 

the average age of miners, may, in part, account for the 

increased proportion of cable handling injuries. 

The severity of injuries associated with handling 

cable varies from relatively minor shoulder strains to 

serious back injuries. The cumulative nature of most 

musculoskeletal injuries implies that other manual tasks 

are likely to have also contributed to these injuries. 

However, there is no doubt that handling continuous 

miner cable represents a high risk of injury and this is 

consistent with biomechanical analysis of the task (Gallagher et al., 2002). Engineering controls are required to 

eliminate or reduce manual cable handling. Integration 

of cable and other services with continuous haulage 

has been suggested in the context of remote control 

(Schnakenberg, 1997).
Vehicle collisions

While vehicle collisions represent a relatively small 

proportion (15 percent) of the injuries associated with 

scoop/LHD, shuttle car and transport, the consequences 

of collisions are frequently severe and include fatalities. This figure is also double the proportion of “collision” related injuries for these vehicles found in recent 

Australian data. The probability of vehicle collisions is 

increased considerably by the restricted visibility inherent in LHD and shuttle cars. This is likely exacerbated 

by the low seam heights. 

This is not a new observation. Reports by Kingsley 

et al., (1980) and Pethick and Mason (1985) described 

the visibility difficulties associated with the design of 

free-steered vehicles. Similarly, Simpson et al., (1996) 

suggested that many underground vehicle collisions 

are at least, in part, a consequence of restricted driver 

visibility. 

The visibility restrictions that driving LHD vehicles 

is one of the few aspects of mining equipment design 

that has been the subject of formal research. The 

research has largely been restricted to documenting 

the extent of the problem and providing methods for 

assessing the lack of visibility associated with current 

designs (Eger et al., 2004). Recommendations for LHD 

redesign arising from the research include raising the sitting position where possible and cab redesign to remove 

visual obstructions. Physical separation of pedestrians 

and vehicles as far as practicable and vehicle mounted 

Although vehicle collisions are infrequent, the consequences are often severe. Rough roads can also contribute to injuries.

proximity sensors and cap lamp battery mounted emitters may also be 

beneficial in preventing potentially 

serious injuries. Examples of proximity detection systems include that 

developed by the National Institute 

for Occupational Safety and Health 

(NIOSH) (Schiffbauer, 2001).

Rough road

Injuries associated with driving 

or traveling in a vehicle that encounters a pothole or other roadway abnormality accounted for 20 percent 

of injuries associated with scoop/

LHD, shuttle car or transport. This is 

lower than the 34 percent of injuries 

associated with this mechanism in 

recent Australian data (BurgessLimerick and Steiner, 2006). And 

this may reflect the greater use of 

rail transport in U.S. mines. 

Even so, improvements in roadway standards to avoid potholes 

and other abnormalities would be 

an effective means of preventing 

injuries of this type. Provision of 

vehicle suspension and improved 

seating have the potential to reduce 

these injuries (Mayton et al., 1997, 

1999). These improvements will also 

reduce exposure to high amplitude, 

whole body vibration, which is 

associated with the development 

of back pain through cumulative 

mechanisms (McPhee, 2001).

Conclusion

The five top priority hazards associated with underground coal mining equipment have been identified and 

information about potential contributing factors and 

controls collated. Consideration of these hazards as part 

of design risk assessments conducted by manufacturers, 

and operational risk assessments conducted by mines 

sites, has the potential to prompt implementation of 

effective control measures. 

Further information and tools to assist this process 

are available elsewhere (Burgess-Limerick, 2007). 

However, as Mark (2002) observed, effective control 

measures will only be implemented when current levels 

of risk are perceived to be unacceptable. The injury narratives revealed a tendency to accept current risk levels 

and focus on individual behavior and administrative 

controls rather than directing attention to elimination 

and design. This must change before significant reductions in injury risk are likely to occur. (References 

are available from the authors.)

Acknowledgements

This research was supported in part by the Australian 

Coal Association Research Program and was undertaken while the first author was a National Academy 

of Sciences, Senior Research Associate at NIOSH 

Pittsburgh Research Laboratory.