Discomfort Glare Comparison for
 

Various LED Cap Lamps
 John J. Sammarco, Senior Member, IEEE, Alan G. Mayton, Timothy Lutz, and Sean Gallagher

Manuscript received June 11, 2010; accepted November 9, 2010. Date of

publication March 10, 2011; date of current version May 18, 2011. Paper

2010-MIC-212, presented at the 2010 Industry Applications Society Annual

Meeting, Houston, TX, October 3–7, and approved for publication in the

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Mining Industry

Committee of the IEEE Industry Applications Society. The mention of any

company or product does not constitute endorsement by the NIOSH. The

findings and conclusions in this paper are those of the authors and do not

necessarily represent the views of NIOSH.

The authors are with the National Institute for Occupational Safety and

Health, Pittsburgh, PA 15236 USA (e-mail: Jsammarco@cdc.gov; anm9@

cdc.gov; tcl9@cdc.gov; sfg9@cdc.gov).

Color versions of one or more of the figures in this paper are available online

at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2011.2126016

Abstract—Researchers at the National Institute for Occupational Safety and Health (NIOSH) are investigating different lighting technologies with the objective of improving mine safety. This 

paper presents the results from an ongoing study that compares 

discomfort glare for different light-emitting diode (LED) cap 

lamps using the de Boer glare rating scale. The cap lamps tested 

included two commercially-available LED cap lamps and one 

NIOSH prototype LED cap lamp tested at three different illumination levels. Prior research indicated that the NIOSH prototype enabled much better visual performance as compared to other LED 

cap lamps. It uses three LEDs that produce multiple illumination 

areas in comparison to commercially-available cap lamps that use 

one LED and projects a narrow spot pattern. Across subjects and 

cap lamp test conditions, measured illuminances (averaged at both 

eyes) varied from 0.62 to 3.73 lx, whereas the de Boer glare ratings 

varied from 4.86 to 7.71. An analysis of variance based on 15 subjects indicated a significant difference in the discomfort glare due 

to cap lamps (F4,52 = 18.01, p < 0.001). Post hoc tests indicate 

that one of the commercially available cap lamps exhibited lower 

discomfort scores, with no statistically significant differences detected between the others. Thus, the NIOSH prototype cap lamp 

does not cause excessive discomfort glare yet enables better visual 

performance. 

Index Terms—Machine lighting, mine illumination, mine safety, 

visual performance. 

I. INTRODUCTION

T HE Illuminating Engineering Society of North America

cites the working face of an underground coal mine as

the most difficult environment in the world to illuminate [1].

Lighting is critical to miners; they depend heavily on visual

cues to spot falls of ground, slip, trip, and fall (STF) hazards,

and pinning and striking hazards from moving mining machinery [2]. An underground mine is a dynamic environment

that includes dust, confined spaces, low reflective surfaces, low

visual contrasts, and glare. Mine illumination typically consists

of a low background light level but a relative high intensity

light spot from a miner’s cap lamp or machine-mounted lighting. This illumination presents high contrast that can lead to

discomfort glare and decreased visibility.

Glare can be defined as the sensation from an uncomfortably

or painfully bright light within a person’s visual field. Glare

occurs from too much light and extremes that produce too broad

a range of light levels compared to those which the eyes are

adapted. The effects of glare on workers include discomfort

glare (annoying or painful sensation), disability glare (reduction

of visibility), recovery or readaptation (visual performance

returning to initial state), and photobiological (optical radiation

effects on living systems). To assess visual performance, one

must consider distinct parameters associated with the glare produced, the environment, and the observer. The factors of glare

that affect visual performance include illuminance at the eye,

angle of the glare source, luminance and size, spectral power

distribution (SPD), and the duration of glare source exposure.

Additionally, visual performance is impacted by environmental

and observer parameters, which include ambient conditions,

complexity of the lighting environment, difficulty of location

with light sources and observers, age, and visual health [3], [4].

Glare studies have been done in the past with underground

coal miners [5], [6]. From a study of discomfort glare with underground coal miners, Guth [6] noted that results indicate that

miners are less sensitive to discomfort glare than office workers.

The evaluation procedure used had been developed for interior

lighting conditions [7]. Concerning disability glare, Crouch

[5] reported in a joint study by Bituminous Coal Research,

Inc., and the Illuminating Engineering Research Institute that

78% of the miners interviewed complained or questioned the

lighting systems relative to discomfort and disability glare,

veiling reflections, and afterimages. From the study results, he

estimated that miners working within the existing illuminated

coal mining face environments could experience as much as a

40% or more loss of visibility. Trotter [8] listed ten methods to

reduce glare. Most of these methods resulted in decreasing the

illuminance at the observer’s eye or increasing the background

luminance with respect to the task luminance.

A number of nonmining studies have investigated glare.

Most studied glare relative to various aspects of automobile

headlamps while driving. For instance, Van Derlofske et al. [9]

and Bullough et al. [10], [11] concluded that the light source

spectrum, as measured by the SPD, played a significant role in

causing discomfort glare but did not play a significant role for

disability glare. Two studies [12], [13] investigated glare recovery according to age. Scheiber [13] noted that the recovery time

for older compared to younger subjects increased by a factor of

three. Bullough et al. [14] reported developing a simple model

using light source photometric characteristics for predicting
discomfort glare from outdoor lighting installations. Using the

model, the authors demonstrated the effect of these photometric

quantities—light source illuminance, surround illuminance,

and ambient illuminance—on subjective assessments of discomfort glare. Moreover, Lulla and Bennett [15] investigated

the range effects associated with discomfort glare. Results of

the study, among other findings, showed that the range of glare

source luminance had a definite effect on the “between comfort

and discomfort levels” of 40 human test subjects. Regarding

the research use of the de Boer subjective rating scale in

evaluating discomfort glare, it is not without its difficulties

and shortcomings. Gellatly and Weintraub [16] studied the de

Boer rating scale [17] for effectiveness in rating discomfort

glare and possible improvements. They suggested that the

scale is not optimal for rating discomfort glare and suggested

improvements. Similarly, Bullough et al. [14] cited that “the de

Boer scale, like all subjective rating research, is prone to difficulties.” They also speak of shortcomings in using the model

described by Schmidt-Clausen and Bindels [18] that was developed for predicting de Boer ratings of discomfort glare from

motor vehicle lighting. Prediction of discomfort glare would

be useful given that the empirical determination of glare requires significant resources involving human subject tests.

Researchers at the National Institute for Occupational Safety

and Health (NIOSH) are investigating different lighting technologies with the objective of improving mine safety by improving visual performance and reducing glare. The scope

is machine-mounted, auxiliary, and cap lamp luminaires for

underground coal and metal/nonmetal mining. Three situations

indicate the need for new research addressing cap lamp glare

in the mining industry and motivate NIOSH research. First, a

miner’s cap lamp is typically the primary and most important

source of light [19]. However, cap lamps are often a source of

discomfort or disability glare which can impact both safety and

task performance. Second, as stated earlier, age is a factor for

glare. This is important to consider because of the aging U.S.

coal mine workforce that has an average age of about 43 years.

Lastly, light-emitting diodes (LEDs) are being used in new cap

lamp designs. LEDs are an emerging technology for mine illumination, and there has been some prior research that addresses

the safety of LEDs with respect to glare. NIOSH researchers

conducted a comparative study of glare from incandescent and

LED cap lamps, as perceived by 30 human subjects [20]. In

this research, the color of light was the primary factor, and

the lighting distribution (beam patterns) was relatively equal

among all cap lamps, given that a diffusion filter was used

to provide homogenous illumination levels and distributions.

The results indicated no statistically significant difference in

discomfort glare among the incandescent and LED cap lamps.

However, an analysis of variance (ANOVA) for disability glare

indicated that the LED cap lamps were superior for the older

subjects. NIOSH researchers also conducted an empirical study

of discomfort glare, as perceived by 36 human subjects, from

machine-mounted area lighting. The lighting technologies were

incandescent, fluorescent, and LED [21]. The results indicated

that the fluorescent machine lights generally were associated

with higher levels of discomfort glare, and lighting conditions

that used LED machine lights were associated with the least

amount of discomfort glare. Currently, NIOSH research of LED

cap lamps is addressing how the cap lamp beam distribution

affects visual performance with respect to detecting tripping

hazards on the floor and detecting peripheral motion, which is

important for avoiding pinning/striking accidents from moving

machinery [22]. However, the effects on discomfort glare are

unknown given various beam distributions.

Therefore, the primary objective of this paper was to determine if LED-based cap lamps with various beam distributions

have an impact on discomfort glare. A secondary objective was

to compare empirical discomfort glare data to results obtained

from predictive models for discomfort glare.

II. METHODS

A. Experimental Design

A randomized complete block (RCB) design (RCBD) was

employed where subjects were treated as blocks and the treatment variable consisted of five glare sources: LED cap lamp 1,

LED cap lamp 2, and a NIOSH prototype LED cap lamp 3

set at three power levels a (high), b (medium), and c (low).

The RCBD randomization was applied only to treatments (glare

sources) within blocks. The dependent variable was subjective

discomfort glare rating. The glare sources were treated as a

within-subjects variable with each subject rating the discomfort

glare based on the de Boer scale. The de Boer scale is a ninepoint subjective scale including qualifiers at the odd points (see

Fig. 1). An RCB ANOVA was used to assess differences in

de Boer ratings between glare sources. A companion analysis

was performed using the Friedman nonparametric two-way

ANOVA to assess the statistical significance between mean

ranks of the glare sources. Glare ratings were factor A and

subject factor B in the Friedman ANOVA on ranks. Post hoc

multiple comparison tests for the Friedman ANOVA followed

procedures provided by Siegal and Castellan [23].

Fig. 1. De Boer scale for rating discomfort glare.

B. Glare Sources

Three LED cap lamps were used. Each cap lamp was brand

new and powered at levels for a fully charged battery. Each cap
lamp used LEDs that were categorized by the manufacturer as

“cool white.” Cap lamps 1 and 2 used a single phosphor-white

LED as the primary light source, along with an optical reflector

to direct the light to a circular spot ranging from about 6◦ to 8◦

as depicted by Fig. 2. Both were approved by the Mine Safety

and Health Administration (MSHA). The third cap lamp was a

laboratory prototype that was developed by NIOSH and tested

at three different power levels. This prototype uses multiple

phosphor-white LEDs as the primary light source along with

secondary optics to direct the light to specific hazardous areas

in the mine as depicted by Fig. 3. The intent is to provide

more illumination in order for miners to better detect STF

hazards located on the mine floor and detect moving machinery

hazards associated with pinning/striking accidents. The NIOSH

prototype LED cap lamp meets the photometric requirements

specified by MSHA [24]. Each cap lamp had beam spots of

varying size and intensity; therefore, the average illuminances

at the subjects’ eyes were as follows: 0.76 lx for cap lamp 1,

2.72 lx for cap lamp 2, 3.42 lx for cap lamp 3 (a), 2.74 lx for

cap lamp 3 (b), and 2.07 lx for cap lamp 3 (c).

Fig. 2. Simulation of the circular beam spot of about 6◦ to 8◦ from cap

lamps 1 and 2. The human model represents the 50th percentile male.

Fig. 3. Simulation of the multiple beam angles from the NIOSH prototype

cap lamp 3. The human model represents the 50th percentile male.

For each cap lamp, the electrical and photometric data are

listed in Table I. Each cap lamp was energized from a regulated

power supply to eliminate voltage fluctuations as a cap lamp

battery discharged. The power supply voltages for the different

TABLE I
 

CAP LAMP ELECTRICAL AND PHOTOMETRIC DATA
 

Electrical Characteristics Photometric characteristics

Cap 

lamp

Supply 

voltage 

(Vdc)

Supply 

current 

(milliamps

Supply 

power 

(watts)

Peak 

wavelength 

(nm)

Correlated 

color temp. 

(K)

1 4.00 760 3.04 452 8039

2 3.95 530 2.09 456 6603

3(a) 2.99 585 1.75 448 6304

3(b) 2.96 450 1.33 448 6356

3(c) 2.75 320 0.88 448 6402

glare source cap lamps were set according to the specifications

for the particular make and model of the cap lamp. These

voltages are representative of fully charged batteries.

Note that Figs. 2 and 3 depict the primary beam angle

which is the angle on each side of the beam axis where the

luminous intensity is 50% of the maximum luminous intensity.

The remaining 50% is dispersed about the periphery of the

beam angle.

C. Subjects

NIOSH personnel at the Bruceton, PA, location were recruited to be subjects. None of the subjects were specifically

involved with this cap lamp research, and most of the subjects

were not familiar with miner cap lamps, or they had used

them infrequently. Only the subjects that passed vision tests

for distance visual acuity, contrast sensitivity, and peripheral

vision were accepted for the study. Subjects that had radial

keratotomy, monocular vision, glaucoma, or macular degeneration were excluded. Subjects were not excluded for color vision

deficiency.

Miners were not used as subjects because of potential expectancy biases that could confound empirical data. Miners

could immediately determine that the bluish-white light from

the LED cap lamps and the lighting distributions from the

NIOSH prototype LED cap lamp were very different from the

yellowish light of an incandescent cap lamp; thus, a negative

bias could exist because the light color and distribution are not

what they are accustomed to, or a positive bias could exist if the

person perceives something new as better.

Fifteen subjects participated: 13 males and two females.

While gender was not a variable in this study, the percentage

distribution for gender was representative of the U.S. miner

population. The average subject age was 54 years. This is

somewhat older than the average U.S. coal miner’s age of

43 years [25].

Subjects signed an informed consent form and were instructed about their right to withdraw freely from the research

at any time without penalty. The protocol was approved by the

NIOSH Human Subject Review Board.

D. Predictive Methods for Calculating de Boer Ratings

Two quantitative methods were used to predict de Boer

ratings of discomfort glare for comparison with the actual de
Boer subjective ratings. The first method included the SchmidtClausen and Bindels equation shown hereinafter as (1) [18]

W = 5.0 − 2.0LOG [Ei/(0.003)

] × (1 + SQRT(LA/0.04))(θ)

0.46 (1)

where

W mean de Boer rating;

Ei illuminance directed at the observer’s eye (in lux);

LA adaptation luminance (cd/m2);

θ angle between the glare source and the observer’s line

of sight.

The second method of predicting utilizes the following (2) and

(3) from [14]:

DG = a log(Ec + Es) + b log(Ec/Es) − c log(Ea) (2)

where

DG discomfort glare;

Ec light source illuminance (in lux);

Es surround illuminance (in lux);

Ea ambient illuminance (in lux).

Coefficients a, b, and c were set at 1.0, 0.6, and 0.5, respectively.

The values of b and c resulted from the best fit of the data

from all of the experiments to the model equation and were

determined through iterative trial and error [14].

The surround illuminance Es was determined by constructing a small baffle of ∼1.6 cm in diameter that slid along a small

cantilever-shaped piece of 15 AWG insulated copper wire. It

was secured to the casing of the sensor measuring surface of

an illuminance meter. The baffle allowed a shadow to be cast

on the sensor so that surround illuminance could be measured

(three for each eye for a total of six measurements). Similarly,

ambient illuminance Ea was measured without the baffle at the

subject’s eyes with the subject incandescent cap lamp providing

illumination.

Once the DG factor was determined, it was inserted into (3)

whereby predicted de Boer ratings were computed

DB = 6.6 − 6.4 log DG. (3)

III. EXPERIMENTAL LAYOUT AND APPARATUS

A. MIL

Testing was conducted at the Mine Illumination Laboratory

(MIL) at the Bruceton, PA, location of NIOSH. The MIL

is a simulated underground coal mine environment that has

various test equipment, data acquisition and control systems,

and networked computers. The interior is 488 cm (192 in) wide

by 213 cm (84 in) high and is coated with a rough-textured

material that has a dark color and a uniform spectral reflectivity

of about 5% for the visible spectrum, which is typical for coal.

B. Observation Station

Each subject was positioned at a fixed known coordinate

with respect to the glare source and de Boer chart, and each

subject’s head position was fixed so that their point of view

was the same regardless of their body size and so that each

subject was tested at an eye height of 165.1 cm (see Fig. 4).

This eye height, with reference to the floor, was based on the

50th percentile standing male [26]. Thus, this eliminated data

confounding from variations in the subjects’ position, point of

view, and eye height. This positioning was enabled by the use

of an observation station designed and constructed by NIOSH

personnel (see Fig. 5). The seat height was designed to accommodate testing of subjects ranging from the 5th percentile

female to the 95th percentile male.

Fig. 4. Plan view of the experimental layout.

Fig. 5. Side view of the experimental layout. Subjects were seated on the

observation station.

C. Experimental Layout

The experimental layout (see Figs. 4 and 5) was arranged to

place the test subject in the observation station facing the test

cap lamps to simulate glare from a coworker’s cap lamp. The

cap lamps were located 312.4 cm (123 in) away from the test

subject at −11◦ off axis from the de Boer chart (see Fig. 1) directly in front of the test subject. The cap lamp glare source was

placed at the eye height of the test subject that was 165.1 cm

(65 in) above the floor. For consistent alignment of each glare

source during testing, a small laser was fastened to the top of the

miner’s hard hat to which each test cap lamp was mounted. The
TABLE II

AVERAGE DE BOER CHART LUMINANCE FOR EACH OF

THE LED CAP LAMP CONDITIONS

Cap lamp Supply power 

(watts)

Average chart 

luminance 

(cd/m2)

None (ambient) 0 0.25

1 3.04 0.30

2 2.09 0.35

3(a) 1.75 0.43

3(b) 1.33 0.40

3(c) 0.88 0.36

laser was directed at a 3.2-cm-diameter chrome magnet (0.5 cm

inner diameter) suspended 7 cm down from the MIL roof just

to the left of the subject (in the direction of the de Boer chart).

D. de Boer Chart Luminance

Luminance in the vertical plane was measured at the de Boer

chart (see Fig. 1) for each LED cap lamp in conjunction with

the ambient lighting provided by the incandescent cap lamp

worn by the subject. The de Boer chart was measured 38.10 cm

(15 in) high by 33.02 cm (13 in) wide and was placed 312.4 cm

(123 in) from the subject (see Fig. 4). Measurements were

made on the de Boer chart at three locations (top, middle, and

bottom). Table II lists the average ambient luminance at the

chart without any glare sources and the average luminance at

the chart for each cap lamp glare source.

E. Procedures

Each subject sat in a darkened environment for 15 min. to

allow the retina to adapt to the dark environment. Next, the

subject was seated on the observation station, and adjustments

were made such that the eye height was 165.1 cm (65 in) from

the floor. While seated, the subject wore a miner’s hard hat with

an incandescent cap lamp illuminated at a power level equal to

that of a fully charged battery.

Prior to the start of the glare experiments, researchers gave

an overview of the experiment to the subjects explaining the

test procedures. In addition, the cap lamps, the glare sources,

and the illuminance meters were switched on and given time

to stabilize (warm up). The subjects were directed to focus

their eyes on the de Boer chart at all times while seated on

the observation station. The vertical illuminance at each of the

subject’s eyes was measured and recorded for the cap lamp

under test. Finally, while sitting in the observation station,

the subjects were asked to think about the discomfort ratings

relative to the designated cap lamp. Subjects subsequently gave

a numerical rating from 1 to 9 for the de Boer chart. The

subject’s response to discomfort glare was manually recorded

once the subject verbalized the rating.

IV. RESULTS

Fig. 6 provides a summary of the mean de Boer ratings

relative to the mean illuminance at the subjects’ eyes (average

of both eyes). Here, the actual subjective ratings are compared with the two quantitative methods for predicting de Boer

ratings. The highest predictive ratings for all five LED cap

lamp conditions were obtained using the simple model from

Fig. 6. De Boer discomfort glare assessments by 15 test subjects compared to

two different predicted de Boer ratings.

Bullough et al. [14], whereas the values predicted using the

Schmidt-Clausen and Bindels equation yielded, in nearly every

case, the lowest de Boer ratings. The average illuminance (both

eyes) for five LED cap lamp glare source conditions is also

depicted. Interestingly, cap lamp 1 deviated from the other test

cap lamps in that it had the worst predicted mean de Boer rating

of about 3.5 (slightly better than disturbing) using the SchmidtClausen and Bindels equation, although the illuminance at the

eyes was lowest.

Considering the results statistically, the RCB ANOVA found

a significant difference in de Boer ratings with different glare

sources (F4,54= 20.15, p < 0.0001). Post hoc tests show that de

Boer ratings were not significantly different for any cap lamps

other than cap lamp 1, which resulted in lower discomfort glare.

Results of the Friedman ANOVA indicated a significant

influence of the glare source on the de Boer ratings (Fr =

32.137, p < 0.001). Table III provides the mean ranks for de

Boer ratings for each of the cap lamps used in this paper and

the result of post hoc multiple comparison tests. The critical

value for comparison of mean ranks was 0.936.

TABLE III
 

RESULTS OF ANOVA POST HOC TESTS FOR RCB AND FRIEDMAN
 

NONPARAMETRIC ANOVA ON RANKS. CONDITIONS
 

CONTAINING THE SAME LETTER ARE NOT SIGNIFICANTLY
 

DIFFERENT FROM ONE ANOTHER
 

RBC ANOVA Friedman 

ANOVA

Cap lamp

Mean de 

Boer 

rating

Sidak post

hoc test

Mean 

Rank

Friedman

post hoc

test

Cap lamp 3a 4.93 A 2.07 A

Cap lamp 2 4.87 A 2.27 A

Cap lamp 3b 5.27 A 2.67 A B

Cap lamp 3c 5.47 A 3.23 B

Cap lamp 1 7.67 B 4.77 C

Results of the multiple comparison procedures (see Table III)

indicated three groups of means that were not significantly

different from one another. Cap lamp 1 had the highest mean

rank (indicating the best de Boer discomfort glare rating) and

was significantly different from all other cap lamps. Cap lamps

3a and 3b were not significantly different from one another,

and cap lamp 2 was not significantly different from cap lamps

3b and 3c.
V. DISCUSSION

A. Subjective de Boer Ratings

The results of the de Boer rating comparisons among the

LED cap lamps indicate that cap lamp 1 had significantly

less discomfort glare than the other cap lamps. While glare is

an important consideration, one must also consider the visual

performance afforded by the cap lamps. The tradeoff for having

less discomfort glare from cap lamp 1 is that this cap lamp

is associated with poorer visual performance with respect to

the detection of tripping hazards on the floor and the detection

of peripheral motion, which is important for avoiding pinning/

striking accidents from moving machinery [25]. On the other

hand, the NIOSH cap lamp 3b afforded the best visual performance, and this cap lamp provided an acceptable level of

discomfort glare. Furthermore, it is interesting to note that cap

lamp 3a gave the highest mean illuminance (3.42 lx) at the eye,

mean luminance level (0.43 cd/m2 + 0.08) at the de Boer chart,

and the largest source luminance of 14 000 cd/m2 yet did not

show a mean de Boer rating worse than “just acceptable −5.”

Cap lamp 1 had the least discomfort glare, mostly likely

because it had the least illuminance at the subjects’ eyes. Generally, discomfort glare increases as the illuminance increases.

Cap lamp 1, attached to the hard hat of the glare source

mounting fixture, pointed down to the floor more than the other

cap lamps; hence, less light was directed to the subjects’ eyes.

One limitation of this paper was that age was not included as

a factor. Prior NIOSH research indicated that this is a significant

factor [20], [21] for visual performance and glare. This research

indicated that glare increases with age. Based on this prior

research, it would be expected that younger subjects would

perceive discomfort glare as less troubling compared to the

glare rating presented in this paper.

B. Predictive Glare Ratings

Considering the de Boer ratings from the human test subjects

and the two predictive methods, there is not much variation

between the de Boer rating methods except for cap lamp 1. The

Schmidt-Clausen and Bindels method gave the lowest (worst)

glare rating of the entire cap lamps tested, which is odd since

cap lamp 1 produced the lowest mean illuminance at the eyes,

which should result in the best de Boer glare rating. Contrasting

the Schmidt-Clausen and Bindels method with the Bullough

[14] method shows the latter method as more in agreement with

the subjective glare rating for cap lamp 1. This may suggest

that multiple illuminances (i.e., from light source, surround,

and ambient condition) are better photometric quantities to

use in conjunction with a simple model to predict discomfort

glare, and it may suggest that the Schmidt-Clausen and Bindels

method has shortcomings for low levels of eye illuminance.

In addition, the range effect mentioned earlier is worth

discussing briefly. The range effect is a tendency for a subject to

use as much of the rating scale as possible relative to the experimental conditions. The range effect may provide an explanation

when comparing the subjective glare rating for cap lamp 1

(de Boer rating of 7.5) with cap lamp 3a (de Boer rating of 4.9).

In this case, the average eye illuminances were 0.76 lx (lowest

of all cap lamps tested) and 3.42 lx (highest of all cap lamps

tested) for cap lamps 1 and 3a, respectively. This large range

of illuminance may have the effect of an artificially higher de

Boer rating for cap lamp 1 given the wide range of illuminance

afforded between cap lamps 1 and 3a.

C. Concluding Remarks

The discomfort glare results indicate that the multibeam

pattern (see Fig. 3) of cap lamp 3b does not pose unacceptable

discomfort glare. NIOSH research has inferred that cap lamp

3b enabled the best visual performance among LED cap lamps

that included cap lamps 1 and 2 described by the research of this

paper. Results show that the cap lamp 3b improved the ability

to perceive objects in the visual field by improving detection

times by as much as 79.5% in peripheral motion detection as

well as a 194.1% detection time improvement for floor trip

objects [22]. Thus, it appears that cap lamp 3b would enable the

best visual performance without the tradeoff of unacceptable

discomfort glare. This research provides important data for

improving the design of future cap lamps and has the potential

to positively affect the safety of employees in the underground

mining industry.

Second, the Schmidt-Clausen and Bindels glare prediction

model seems to have limited usefulness given that it erroneously predicted cap lamp 1 had the worst discomfort glare.

Empirically, cap lamp 1 had the best discomfort glare. The predictive discomfort glare model by Bullough appears to be more

useful given that it more closely matched the empirical data.

Lastly, the research presented in this paper was conducted

in a simulated mine with human subjects that were not miners.

Our next logical and planned step is to conduct a field comparative evaluation of the NIOSH LED cap lamp in a coal mine,

using miners as the test subjects.

ACKNOWLEDGMENT

The studies described in this paper were conducted with

assistance from J. Srednicki, J. Carr, T. Matty, and T. Minoski.

The vision testing was conducted by M. A. Rossi, R.N., and all

employees of the National Institute for Occupational Safety and

Health (NIOSH) at the Bruceton, PA, location.

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John J. Sammarco (SM’91) received the B.S. degree in electrical engineering technology from The

Pennsylvania State University, University Park, in

1978, the M.S. degree in industrial engineering from

the University of Pittsburgh, Pittsburgh, PA, in 1986,

the M.S. degree in computer engineering from the

National Technical University of Fort Collins, CO,

in 1986, and the Ph.D. degree in computer engineering from West Virginia University, Morgantown,

in 2003.

He is currently a Senior Research Engineer with

the National Institute for Occupational Safety and Health, Bruceton Facility,

Pittsburgh. His Federal service has been devoted to mine safety research

in a wide variety of areas, including mining machine navigation and guidance, control systems, and sensors. His recent research areas concern system

safety, hazard/risk analysis of processor-controlled mining systems, smart

wireless sensors, visual performance, and solid-state lighting systems for mine

applications.

Alan G. Mayton received the B.S. degree in mining

engineering from West Virginia University in 1978.

He serves as Research Engineer in the Musculoskeletal Disorders Prevention Team of the Office

of Mine Safety and Health Research, Human Factors

Branch, National Institute for Occupational Safety

and Health, Pittsburgh, PA. His primary interests

include the application of current LED lighting technology to underground mining, human body vibration control, vehicle dynamics, ergonomic design

of seats and operator compartments, and improved

knee-pad design for low-seam coal miners.

Mr. Mayton is a member of the American Society of Mechanical Engineers

(ASME), the Vehicle Design Committee of the ASME Design Engineering Division, the International Minerals Association of North America—Ergonomics

Task Force, and the International Society of Mine Safety Professionals. His

memberships also include the Human Factors and Ergonomics Society (HFES)

and the HFES Industrial Ergonomics Technical Group. He is a Certified Mine

Safety Professional and a Registered Professional Engineer in Pennsylvania.

Timothy Lutz received the B.S. degree in mechanical engineering from The Pennsylvania State University, University Park, in 1983.

He is a Research Engineer with the Mining Injury Prevention Branch, National Institute for Occupational Safety and Health, Bruceton Facility,

Pittsburgh, PA. He began his mining research career

at the U.S. Bureau of Mines in 1990, in a variety of

safety areas. Since 2005, his research has included

underground mine lighting using LED technology

which has emerged as an efficient and durable alternative to existing lighting.
 

Mr. Lutz is a Registered Professional Engineer in Pennsylvania.
 

Sean Gallagher received the Ph.D. degree in industrial and systems engineering from The Ohio State

University, Columbus, in 2003. His dissertation examined the tolerance of the lumbar spine to repeated

loading during lifting in forward bending postures.

Since 1984, he has been performing research to

reduce musculoskeletal disorder risk in the mining

industry, initially with the U.S. Bureau of Mines and

currently with the National Institute for Occupational

Safety and Health, Pittsburgh, PA. A major interest

has been to quantify the physical demands associated

with work in the underground coal mine environment and the biomechanical

and physiological effects of working in restricted workspaces.