o 5 

A pilot study of the role of visual attention locations 

and work position in underground coal mines 

By John R. Bartels, Sean Gallagher and Dean H. Ambrose 

OPERATING LARGE MOBILE EQUIPMENT such 

as a continuous miner (Photo 1) is one of the most 

dangerous jobs tha t workers perform in W1derground coal mining. When undergroW1d coal is 

mined by the room-and-pillar method, rooms are 

formed by cutting into the coal bed (seam), leaving a 

series of pillars or columns of coal to help support 

the mine roof and crea te passages for the flow of 

fresh air. Generally, a completed room is 4.9 to 6.1 m 

(approximately 16 to 20 ft) wide and the pillar is 30.5 

to 36.6 m (approximately 100 to 120 ft) wide. As mining advances, a grid-like pattern of rooms and pillars 

is formed, resulting in entries of horizontal mine 

passageways (Figure 1). 

The Continuous Mining Process 

Typically, to begin a room, the continuous miner 

engages in cutting (removal) a 3 m (9.8 ft) wide sechon of coal to a depth determined to be safe based 

on local geologic conditions and mining regulations-on average up to 6.1 m. Deeper cuts can be 

made (called extended-cut mining) with special permission from state and federal mining regulators. 

After the cut coal is loaded onto haulage vehicles, 

the operator then backs the continuous miner out of 

the partially formed room, repositions the machine, 

and reenters to begin removing an additional 3 m 

section of coal to produce a wider entry. This process 

is repeated until a section of the seam is removed, 

forming a room approximately 12.2 m (approximately 40 ft) long and 6.1 m wide. 

By law, roof support is required before continuing 

to extend the room's depth or cutting perpendicular 

to the room. Therefore, to allow other equipment to 

install roof support, the continuous miner is 

trammed (moved) to another location to begin cutting another room. Throughout the mining sequen e, 

when forming rooms or tramming to another location, the machine operator, helpers, crew boss, maintenance mechanics and other equipment operators 

are put at risk by close proximity to the continuous 

miner machine and other hazardous situations associated with mining LmdergroW1d coal. 

MSHA accident data from 2002 to 2006 indicate 

that the coal industry averages 6,407 accidents per 

year in W1derground mines. Of those total acciden ts 

per year, 21 % (1,345) involve mobile face equipment, 

which includes continuous miners, roof bolters and 

haulage vehicles for undergroW1d mines; 4% (286) 

occurred while operating continuous mining 

machines. UnfortW1ately, in relation to this study, 

MSHA accident investigation reports do not contain 

sufficient information to aid in studying interactions 

between a machine and its operator. Consequently, a 

survey conSisting of a questionnaire was used to 

gather pertinent information about operating a continuous miner in W1dergroW1d coal mines. 

In the past, a continuous mining machine was 
operated and controlled by 

an operator seated in the 

onboard machine cab. New 

remote control technology 

allows operators more flexibility to position themselves 

to better view the work environment. Unfortunately, it

has also allowed operators to 

position themselves in hazardous positions. 

Photo 1: Operating large mobile equipment such as a continuous miner is one of 

the most dangerous jobs that workers perform in underground coal mining. 

Figure 1: When underground coal is mined by the 

room-and-pillar method, rooms are formed by cutting into the coal bed, leaving a series of pillars or 

columns of coal to help support the mine roof and 

create passages for the flow of fresh air. 

Abstract: Underground 

coal mine mobile equipment is often operated 

in a restricted workspace 

with reduced visibility. 

This puts machine operators in awkward postures for tasks that 

require awareness of 

their surroundings and 

fast reactions to avoid 

hazardous situations. 

Researchers conducted a 

pilot investigation that 

developed a method to 

gather visual attention 

locations and work positions used by machine 

operators while controlling the machine. 

The use of radio remote 

control frees operators from 

the onboard cab and allows 

them to select any operating position within their line of 

sight. While cutting coal remotely, the operator typically takes a work position behind and to one side of 

the machine behind the last row of roof support. In 

high coal seams, where the machine is less of an 

obstruction, the operator trams the continuous 

miner using a remote control while walking near the 

rear of the machine. In low coal seams, the operator 

cannot see over the machine from the rear, so s/he 

trams the machine using a remote control while 

walking near the front of the machine. 

However, operators tend to step alongside a 

moving continuous miner or beyond the supported 

roof for a better view while coal cutting or tramming. Adding to this hazard is restricted work space 

with reduced visibility. The work environment in 

found in low coal seams of 15.7 cm puts continuous 

miner operators and helpers in awkward work postures for the job, with tasks requiring quick reactions 

to avoid being struck by moving equipment. 

Research has confirmed that modem mining practices and new technology have increased the risks 

involved in continuous miner machine operation. 

Bauer, Steiner and Hamrick (1994) report that the 

practice of extended-cut mining has increased operators' tendency to position themselves in hazardous 

locations. Additionally, Steiner, Turin and Hamrick 

(1994) state that an unforeseen consequence of remote 

control technology is that operators can position 

themselves in dangerous or hazardous locations 

which could result in a fatality or injury from possible 

roof falls, mine wall breakouts, pinch-points or other 

vehicle traffic. Finally, Lewis (1986) notes that low 

lighting conditions and restricted visibility found in 

many mines further complicate the tasks involved in 

operating equipment such as continuous miners. 

The mining industry uses an operator guideUne 

called red zones to help operators of remote continuous 

miners understand and avoid dangerous areas 

around the turning radius of the machine. While the 

concept of the red-zone technique, a pictorial go/nogo chart-developed by MSHA and the Virginia 

Department of Mines, Minerals and Energy (MSHA, 

2004)-has been around for several years, fatalities 

and injuries continue to occur with moving machinery 

underground. The red-zone guide only addresses 

potential hazardous situations, ignoring the issue of 

what operators need to see and consequently where to 

position themselves in order to perform their jobs. 

Human/machine interactions and behaviors 

should be considered in equipment design and work 

environment layout. After analyzing the data presented in this article, one can see that the practice of 

operators positioning themselves in a hazardous 

position in order to see visual attention locations 

(VALs) may be a major contributing factor to injuries. 

A VAL can be defined as either a discrete point 

such as center of the cutting head or a general area 

that an operator visually scans such as the mine 

rib. Previous studies by Sanders and Kelley (1981) 

have provided a baseline of VALs that identified factors· associated with cab-mounted operation of continuous miners. However, the information is not 

completely applicable to today's remote control operation. Approaches to determining operator VALs 

were also developed by Cornelius, Steiner and Turin 

(1998), who identified operator visual cues in extended-cut mining based on coal miners' experience. 

The purpose of the study described here was to 

perfect a method of gathering information on work 

positions and VALs needed by operators during the 

cutting phase and while the continuous miner trams 

to a new location. This study precedes a future in-
vestigation using the developed survey that will recommend injury prevention interventions based on 

the influence of work positions and VALs on the risk 

of potential injury. 

Study Method 

The Survey 

A pilot survey was used to collect information on 

VALs from 12 continuous miner machine operators 

with experience ranging from 2 to 30 years at seven 

mine sites. A scripted interview technique was 

selected as the most efficient method of collecting 

and consolidating this information. The pilot study 

was used not only to collect information but also to 

judge the effectiveness of the questions in extracting 

the desired data. 

The survey evolved through a series of discussions by individuals with years of mining research 

and continuous miner operator experience. Experienced operators have a wealth of knowledge, skills 

and abilities regarding machine job tasks, gained 

from years on the job. Researchers determined 

which phases of the continuous miner work 

sequence should be studied based on a combination 

of statistical information from MSHA's annual mine 

accident database, Sanders and Kelley's research 

(1981), and job task analyses for machine operators. 

The survey covered two components of the continuous miner work sequence: 1) the cutting phase 

with 15 questions and 2) the tramming phase (movement from one location to another) with 16 questions. 

Each component was field tested at seven mine operations to evaluate effectiveness of questions and 

value of the data collected. In addition, during the 

mine visits, researchers arranged to go lmderground 

after the interview to observe the operator performing his job. These observations helped the researchers 

evaluate the data collected during the interview and 

validate the responses. 

Table 1 

Example of Questions 

When you take a straight cut from where you are normally located, how 

often do you use the following as reference points? 

How often Things you look at Always Sometimes Never 

Edge of the machine on the side 

you are on 

Center line of the machine 

Back end of the boom 

Cutting head bits 

How far the boom swings 

Spray nozzles 

Haulage vehicle inby bumper 

Hauliage vehicle operator 

Floor at the face 

Roof at the face 

Right edge of drum 

Left edge of drum 

Center or other point on the drum 

Ribs on left side of miner 

Ribs on right side of miner 

Laser beam/spot 

Center line of entry 

Key Mining Terms 

Continuous miner: Mining machine designed to 

remove coal from the face and to load that coal into cars or 

conveyors. 

Cutting: Operation of making openings across a 

coal seam. 

Cutting drum: Rotating drum with carbide teeth that cuts 

the coal from the seam. 

Extended cut: Cutting an entry that is more than 20 ft 

long without stopping to support the roof. 

Face: Exposed surface of a coal or ore deposit in the 

working place where mining is proceeding. 

Floor: Bottom of a coal seam or any other mineral deposit. 

Haulage: System of hauling coal out of a mine (usually 

mobile vehicles or conveyor). 

Highllow coal: Coal seam of 48 in. or more is considered 

high; less than 48 in. is considered low. 

Pillar: Column of coal or ore left to support the overlying 

strata or hanging wall in a mine, generally resulting in a 

room-and-pillar array. 

Red zone: Area around an operating machine that should 

not be entered for safety reasons. 

Roof: Rock immediately above a coal seam. 

Roof support: System for preventing fall of roof in mines. 

Boreholes usually from 1 to 4 m (3 to 12 ft) long are drilled 

upward in the roof, and bolts of 2 to 2.5 em (~to 1 in.) or 

more in diameter are inserted into the holes and anchored at 

the top by a split cone, mechanical anchor or resin grout. 

Room: Place abutting an entry or airway where coal or 

ore has been mined. 

Room and pillar: System of mining in which typically 

flat-lying beds of coal or ore are mined in rooms separated 

by pillars of undisturbed rock left for roof support. 

Seam: Stratum or bed of coal or other mineral; generally 

applied to large deposits of coal. 

Section: Portion of the working area of a mine. 

Tram: Moving a self-propelled mobile machine from one 

place to another. 

Ventilation: Mine workings are usually subdivided to 

fonn several separate ventilating districts. Each district is 

given a specified supply of fresh air and is free from contamination by the air of other districts. 

Water spray: Wetting of a surface while cutting to reduce 

airborne dust. 

Note. Originally compiled by the U.S. Bureau of Mines. Additiollill definitions can be obtained at lllww.infomine.comidictionary. 
An operator must assimilate and process several 

VALs and machine feedback cues to safely control a 

continuous miner. The survey questions were 

designed to provide data not only on what the operator looks at and from what position, but also on 

why an operator uses certain visual cues and 

machine feedback cues to make decisions on how to 

operate the equipment and select a work location. 

For example, questions addressed possible 

obstructions such as dust, water spray, light housings 

and the glare from light sources that might block the 

operator's view of vital VALs, and the operator was 

asked what he would do about these obstructions. 

Also, a series of questions dealt with initial work 

positions, operator postures and possible deviations 

from that initial position during the work sequence 

while operating the continuous mi.ner. 

Due to the restricted work environment and conditions such as low seam height, the operator may 

not always be able to see essential VALs. Experienced operators tend to substitute other cues when 

this happens. For example, the cutting drum on the 

continuous miner will make a task-specific sound or 

vibration, indicating that the machine is cutting into 

the roof or floor outside of a coal seam. This does not 

mean that the roof and floor become invalid VALs, 

but they are blocked from view in this instance. 

Because of this, the survey included questions about 

the machine feedback cues and how the operator 

uses this information to perform the job. 

Underground mine configurations and coal 

removal plans vary at each mine operation based on 

mining preferences, seam height and local geology. 

Consequently, the cutting phase to complete a room 

can take four separate cuts, tvvo longer cuts or even 

one cut if the continuous miner (full-face miner) is 

fitted with the cutting appendage wide enough to 

accommodate the planned width of the room. The 

method of hauling and loading coal is also wideranging, involving such options as continuous 

haulage systems, shuttle cars and front-end loaders. 

Despite these variations, much of the information 

an operator requires in the way of visual cues to 

operate the continuous miner is the same. For this 

reason and to normalize the da ta, the survey used 

various illustrations that apply to a broad range of 

mining operations and mine environments as interview aids. The differences between mining configurations can be divided into three general layouts 

based on the type of haulage and width of the cut. 

Other differences include a variation in the 

sequence of cutting patterns, such as taking the first 

cut on the left rather than on the right side of the new 

entry. The set of illustrations used at a particular site 

was based on a previsit interview with mine management to determine mining methods and cutting 

sequences used at that operation. 

In particular, these illustration aids helped to 

identify the operator's work positions and the VALs 

specific to an area, a particular spot or other objects 

(people and machines) within that operation's work 

environment. 

~ 

0.) 0" 

Oil 

Tramming 

OJ 

Interview Technique 

The data were collected using a scripted interview technique following survey questions as the 

outline. The interviews were conducted at the mines 

during the shift change in aboveground settings 

such as the bath house or maintenance shop, since 

operators do not typically have enough time for 

interviews while working underground. In addition, 

through field trials of the survey, the aboveground 

locations proved to be convenient for conducting 

multiple interviews and confirmed how relaxed and 

focused operators were with their responses. 

Each interview lasted about 1 hour and was conducted by two researchers, one who recorded while 

the other conducted the interview. The interviewer 

acted as a facilitator, so the other researcher recorded the responses in detail, because many questions 

were designed to lead the operator into comprehensive discussions rather than just a one- or two-word 

answer. This two-person approach allowed ample 

time to focus the interview and concentrate on 

understanding each operator's rationale in his decision making to process a lot of informa tion for controlling the continuous miner. 

Tailored to reflect the specifics of each mine visit, a 

series of colored, 3-D illustrations was prepared as a 

visual aid depicting that mine's sequence of tasks and 

underground coal mining equipment. These illustrations aided in the interview process and recording of 

the responses. It was obvious to researchers that the 

use of visual aids helped the operators explain where 

and why they positioned themselves, and identify 

discrete points or general areas they watched while 

operating the continuous miner. 

OJ 

Figure 2: Work positions during cutting 

and tramming. 

In addition, the survey contained tables (such as 
Table 1, p. 30), Hsting locations where the operator 

might look while controlling the machine and with 

what frequency (i.e., always, sometimes, never). 

These tables made it easier for operators to formulate 

their responses by identifying VALs that they would 

use and provided them the opportunity to discuss 

probable reasons for their choices. This infonnation 

helped researchers detennine the importance of the 

operators' choice in their responses associated with 

each VAL listed in the tables. 

After completing each interview, responses were 

examined for possible adjustments to the survey. 

The first three interviews led to minor adjustments, 

such as rewording a question, changing question 

sequence, or modifying contents to clarify a table or 

an illustration. The changes were considered effective when the operators being interviewed no longer 

asked for clarification on the questions or had suggestions to make the questions clearer. These adjustments were made for clarity and flow of the 

interview and would not have changed responses 

from the three previous interviews. 

Data Analysis 

The data revealed three types of cues an operator 

uses to control the machine: visual, audible and tactile. The operator responses indicated that VALs 

were the most important and that the other cues 

were used as substitutes when visual information 

was obscured or restricted. After an interview had 

been reviewed and analyzed, it was validated by 

observing interviewed operators performing their 

jobs. This verified that they were constantly 1) monitoring multiple VALs by scanning the work area; 

2) checking machine feedback during operation; and 

3) routinely observing the location of other workers 

and equipment in close proximity of the work area. 

In addition, it was observed that operator location 

could be dynamic, changing as the situation 

required. Figure 2 (p. 31) shows the frequency with 

which operators identified specific work positions 

during both the cutting and tramming tasks. 

The VALs and the work positions that the operators considered vital were consistent from mine to 

mine. Table 2 summarizes data collected on visual 

attention locations for the cutting phase and Table 3 

presents data for the tramming phase. 

Table 2 

VAL Frequency Cutting 

When you take a straight cut from where you are normally located, how 

often do you use the fol lowing as reference points? 

How often 

Things you look at Always Sometimes Never 

Edge of the machine on the side you 8 1 3 are on 

Center line of the machine 3 5 4 

Back end of the boom 8 4 -

Cutting head bits 5 4 3 

How far the boom swings - 4 8 

Spray nozzles 1 4 7 

Haulage vehicle inby bumper 1 4 7 

Haulage vehicle operator 3 7 2 

Floor at the face 7 2 3 

Roof at the face 11 1 -

Rlight edge of drum 4 8 -

Left edge of drum 5 7 -

Center or other point on the drum 2 8 2 

Ribs on left side of miner 3 7 2 

Ribs on right side of miner 5 5 2 

Laser beam/spot 5 2 5 

Center line of entry 9 3 -

When taking a straight cut from where you indicated you normally 

position yourself, do any of these things block your view of things you 

need to see? 

How often 

Things that block your view 

Always Sometimes Never 

Glare of machine lights - 7 5 

Machine light housing - 2 10 

Spray from nozzles 2 4 6 

Steam from bits 1 1 10 

Dust 8 3 1 

Ventilation system (response reflects 

both or just one system used) 

Brattice 1 2 4 

Tubing 3 2 3 

Coal piles on machine 2 6 4 

Bolter operator on miner bolters-not - 2 6 all mines use this machine 

Do you ever turn the drum off for - 5 7 visibility 

VALs are 

defined as a general area around the machine, a specific point on the machine, or a mobile object such as 

another person or machine around the continuous 

miner machine. Some VALs are machine appendages 

associated with a direction of movement such as 

up / down, swing left, swing right or swing centered. 

Those VALs around the continuous miner that have 

movement-such as people and other machine operators-are defined as mobile to imply the possibility 

of moving in any direction. 

Many VALs are the same for both the cutting and 

tramming phases, although the reasons for their 

importance may differ. For example, in the cutting 

phase, the tail of the continuous miner is watched 

while loading the haulage vehicle with coal. In the 

tramming phase, the operator watches the machine's 

tail to avoid hitting the roof when uneven floor causes the machine to Lmdulate or when turning a comer 

to avoid striking the side of the coal seam. 

As expected, the data showed that the line of 

sight to VALs plays a major role in the operator's 

decision on where to stand during the job. Observing operators underground proved to re-
searchers that operators tried to select a work position which provided the best line of sight to VALs. 

However, other factors also seemed to influence 

the selection of a work position such as equipment 

concerns or mine layout. An example of an equipment 

concern is the need to not run over the electrical cable 

that supplies power to the continuous miner. A mine 

layout example affecting work position is the requirement that operators stand close to a source of ventilation which supplies fresh air and removes dust from 

the work area. These factors limit which work positions an operator would use at a particular mine. 

Table 3 

VAL Frequency Tramming 

When you tram the miner from where you are normally located, how often 

do you use the following as reference points? 

How often 

Things you look at 

Always Sometimes Never 

Edge of the miner on the side you are on 5 - -

Center line of the miner (paint or laser) - 1 4 

Any edge of the boom 2 3 

Cutting head bits 4 - 1 

Spray nozzles 4 - 1 

Floor of the entry 3 1 1 

Roof of the entry 4 1 -

Right edge of drum 3 2 -

Left edge of drum 2 3 -

Center or other point on the drum 3 2 -

Ribs on left side of miner 2 3 I -

Ribs on right side of miner 3 2 -

Center line of entry - 3 2 

Back end of boom 3 2 -

When you tram the miner from where you are normaHy position yourself, 

do any of these things block your view of things you need to see? 

How often 

Things that block your view 

Always Sometimes Never 

Glare of machine lights - 3 2 

Machine light housing - - 5 

Spray from nozzles - 1 4 

Dust . 1 4 

Ventilation system 

Brattice - 2 1 

Tubing - 1 2 

Coal piles on machine - 1 4 

Other machines 3 2 - Other people 2 3 -

Results 

An example of results from interview questions 

that helped to develop a list of VALs is shown in 

Tables 4 (p. 34) and 5 (p. 35). Operators were asked to 

indicate how frequently they looked at specific VALs. 

Other question...s were more subjective, allowing operators to provide additional information that the survey had not covered. This combination of questions 

allowed for a prioritized list of VALs to be generated. 

The data generated can be analyzed by various 

techniques with the goal of improving operator safety. The determination of operator work positions, for 

example, can be compared to Figure 3, which represents injury zones derived from the MSHA accident 

injury database.

Figure 3: 

Operator injury 

zones derived 

from MSHA's 

injury database. The 

zones are 

divided by the 

type of injury 

most likely to 

occur in that 

zone. 

The zones are divided by the type of 

injury most likely to occur in that zone. 

An example would be injuries in zone B, which 

would most likely be the result of a crush.ing accident by the tail boom. By comparing the frequency 

of injuries in a particular zone with the operator 

posi tion frequency, reconunenda tions can be made 

on preferred positions. 

The data also permit the use of simulation tools to 

determine which VALs are blocked from the operator's view at any work position at a desired point in 

the mining cycle. The results gathered from 12 operators were used to determine operator positions in a 

simulated environment using a digital human model 

and simulation software. VALs were represented as 

individual points for a VAL that represented a specific point on the machine, or as a matrix of points for 

VALs associated with a general area. By representing 

areas as a matrix of points, the percentage of the area 

seen or blocked from the operators' view-from any 

perspective--could be determined. The operator 

could then be placed in any of the work positions 

determined from the data (Figure 4, p. 34). 

Figure 5 (p. 34) represents the perspective view 

from the digital human's eyes of what the operator 

might see from any position. These perspective 

views allowed researchers to analyze the positions 

that the operator takes trying to see VALs while operating the machine. These views helped to reveal how 

limited an operator's field of view can be. The scanning feature of the software allows for an automatic 

determination of which VALs are seen or blocked 

from any position. This allows a numerical means of 

comparing one work position to another, which can 

then be compared to the accident injury zones. 

To demonstrate, the operator's field of view 

improves on the left cut, but so does the temptation 

to move forward for a better view and, consequently, move underneath unsupported roof-which is 

not only illegal, but also wlsafe. By comparing the 

operator's view at different positions, insight can be 

gained into the VALs the operator needs to control 
the machine safely as well as positions where the 

operator could be at greater risk. 

This i.nform.ation helped researchers to determine 

the importance of the operators' positions in their 

responses associated with each job task. Additionally, 

the i.nformation indicated the importance of the operators' choices in their responses associated with each 

of the VALs listed in the tables. Furthermore, it provided the operator the opportunity to discuss probable reasons for the choices made. 

Table 4 

Most Important VALs Cutting 

Direction of VAL Area/spot/object:f: movement 

Last row of bolts area -

Center line of entry area -

Center line of machine area -

Rib right side area -

Rib left side area -

Edge of machine right side area -

Edge of machine left side area -

Top of drum at center area up/down 

Bottom of drum at center area up/down 

Right edge of drum spot up/down 

Left edge of drum spot up/down 

Roof at right edge of drum spot -

Roof at left edge of drum spot -

Floor at right edge of drum spot -

Floor at left edge of drum spot -

Center line of machine at drum spot -

swing End of tail boom spot left/right/center 

Roof at tail boom spot -

Floor at tail boom spot -

Cut depth mark added to 

spot - machine 

Haulage machine (shuttle car, object mobileO mobile bridge) 

Operator of shuttle object mobile car/bridge/ram car 

Face boss object mobile 

:t: Area: specific area around the machine; spot: specific point on the 

machine; person: another worker around the machine. 

o Mobile VAL is located near the continuous miner machine and moving in 

any direction. 

Figure 4: The 

data gathered 

permit the use 

of simulation 

tools to determine which VALs 

are blocked from 

the operator's 

view at any 

work position at 

a desired point 

in the mining 

cycle. 

Figure 5: Operator's eye view, which allows the 

researchers to analyze the positions that the miner 

takes trying to see VALs while operating the machine. 

Discussion 

The results of this pilot study showed that the 

method of data collection and analysis successfully 

identifies the work positions and the quality of information available to a continuous miner operator to 

conh"ol the machine safely. With the help of research 

tools such as computer models and simulations to 

evaluate visual data, the results of this article reveal 

that knowing the work positions and visual needs of 

operators in performing their job has the potential to 

improve both equipment design and machine operating practices. Additionally, Mason, Rhodes and 

Best (1979) report that the use of the operators' specific locations and visual perspectives as a training 

tool could help operators make better decisions on 

safe work position. 

A 3-year study using the developed interview is 

currently undelway to provide an in-depth examination of the VALs, operator positions and machinE! 

feedback cues that operators use for controlling a 

continuous miner. A larger number of interviews (70 

to 100) are planned at mine operations throughout 

the U.s. to analyze the VALs, work positions and 

their relative importance to the machine operator. 

I~anking the VALs will allow improved evaluations of each job phase for all mining configLU'ations; 

however, a larger database is needed to do this. A 

larger database must have a better representation of 

operators and mining methods from a cross-section of 

underground mine operations in both eastern and 

western states. Additionally, the complex relationships between visual locations must be defined. For 

example, an operator on the right side of the machine 

might be able to imagine the VALs on the left side of 

the cutting drum if the right side of the drum is visi-
ble. Also, with a larger and 

more diversified database, comparing work positions and necessary VALs to injury data will 

be investigated. How these 

relationships apply in different 

situations, the operators' dependence on them, and potential control interventions 

adapted to machines to enhance 

VALs and optimize operator 

positions will be explored. 

Results indicate that the survey and underground observations were a good combination 

and technique to develop a 

database of important visual 

cues and locations an operator 

can see from a given work 

position and posture. Analysis 

techniques that determine 

which VALs an operator sees 

from a variety of positions in a 

computer simulation is shown 

to be potentially useful to the 

mining industry for design of 

work practices and section layout, and could impact equipment design or selection 

for improved worker safety 

through training. Based on the 

promising results of this study, 

an in-depth examination of 

operator cues and positioning 

is underway. 

Table 5 

Most Important VALs Tramming 

Direction of VAL Area/ spot/ object:J: movement 

Center line of entry area -

Center line of machine area -

Rib right side area -

Rib left side area -

Edge of machine right side area -

Edge of machine left side area -

Roof at center of drum area -

Top of drum at center area up/down 

Centerline of entry at 20 ft area -

Roof at 20 ft area -

Centerline at necessary area - stopping distance 

Roof at necessary stopping area - distance 

Floor at necessary stopping area - distance 

Obstacles at necessary area - stopping distance 

Right edge of drum spot up/down 

Left edge of drum spot up/down 

Roof at right edge of drum spot - I 

Roof at left edge of drum spot -

Floor at right edge of drum spot -

Floor at left edge of drum spot -

Center line of machine at 

spot - drum 

swing End of tail boom spot left/ right/center 

Roof at tail boom spot -

Floor at tail boom spot -

Cut depth mark added to 

spot - machine 

Other moving equipment object mobileO 

Mechanic object mobile 

Face boss object mobile * Area: specific area around the machine; spot: specific point on the 

machine; person: another worker around the machine. 

o Mobile VAL is located near the continuous miner machine and moving 

in any direction. 

References 

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A.W., et aJ. (2008). Virtua.l design modifications yield line-of-sight improvements for LHD operators. InternntioHal 

Journal of IndustriaT Ergol1omics, 38(2), 

202-210. 

Bauer, E., Steiner, L. & Hamrick, C. 

(1994). Extended-cut mining and worker safety in underground coal mines. 

Society for Mining Metallurgy and Exploration (preprint 95-60). 

Cornelius, K., Steiner, L. & Turin, F. 

(1998). Using coal miners' experience to 

identify effective operating cues. Proceedings of the HunU1n Factors and Ergo110mics SociehJ 4211d Annual Meeting, 

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