CHARACTERIZATION OF JOLTING AND JARRING ON OPERATORS OF SURFACE
 

MINE HAULAGE TRUCKS 

by Fred Biggs, Richard Miller, and Walter Utt 

ABSTRACT 

Powered haulage has been, and continues to be, a major source of severe accidents and 

fatalities at metal/nonmetal surface mines. Between 1986 and 1997, truck drivers accounted for 

63% of the lost-time injuries in surface haulage. This project was undertaken to reduce the 

number and severity of lost-time injuries among operators of these trucks. Work involved 

measuring shock acceleration at a western surface mine during representative work cycles on two 

types of trucks and collecting data from cab floors using a triaxial accelerometer and from 

operator seats using a seat pad accelerometer. NIOSH researchers also used the mine’s GPS 

systems to locate shock events on a mine map in real time. Shock tests were also run at 

Caterpillar, Inc.’s, proving grounds in Green Valley, AZ, to determine the magnitude of shocks 

resulting from controlled rock drops onto the bed of a haulage truck. 

INTRODUCTION 

Powered haulage has been, and continues to be, a major source of severe accidents and 

fatalities at metal/nonmetal surface mines. Between 1986 and 1997, injuries to truck drivers 

accounted for 63% of the lost-time injuries. 

The objective of this research is to reduce jolting and jarring injuries among operators of 

heavy mining equipment, particularly haulage truck drivers. Characterization of the magnitude 

and frequency of jolts and jars will lead to a better understanding of their causes and enable 

researchers to evaluate different types of engineering controls that could reduce trauma to 

operators and lower the incidence of back injuries. The research is part of a project called 

“Engineering Controls for Reducing Jolting/Jarring Injuries in Surface Mines” at the Spokane 

Research Laboratory (SRL) of the National Institute for Occupational Safety and Health 

(NIOSH). In this project, researchers are investigating the causal factors of jolting and jarring, 

what combination of jolts and jars is likely to harm an operator, and the cumulative effects of 

long-term exposure to jolting and jarring. 

FIELD TESTS 

Data were collected under actual field conditions during representative work cycles at a 

western surface mine interested in reducing lost-time injuries among its haulage truck operators. 

These data were obtained from two types of haulage trucks (truck A and truck B) manufactured 

by different companies. Jolts and jars were measured using an 8-megabyte Dallas Instruments 

Saver mounted to the pedestal of the driver’s seat with a strong magnet at the point where the seat 

is bolted to the cab floor. This instrument package has an internal piezoelectric triaxial 
accelerometer that measures accelerations at the pedestal. A Bruel and Kjaer type 4322 triaxial 

seat pad piezoelectric accelerometer measures acceleration at the cushion. The three orthogonal 

directions (x, y, z) were oriented according to ISO 2631 [1]. From the driver’s perspective, x is 

positive forward, y is positive to the driver’s left, and z is positive upward. 

For truck A, the Saver monitored jolting and jarring for 11 hr, 37 min, between 2:45 p.m. on 

June 8 and 7:08 a.m. on June 9, 1999. For truck B, the Saver monitored jolting and jarring for 

18 hr, 1 min, between 12:47 p.m. on June 9 and 6:48 a.m. on June 10, 1999. The threshold for 

triggering data collection was determined empirically at 1.5 g’s on the z channel of the seat 

cushion. Seven events above 1.5 g’s were recorded on truck A, and five events were recorded 

on truck B. Other set-up parameters were filter frequency, 200 Hz; range, ±50 g’s; samples per 

second, 512; recording time, 8 sec; and samples per event, 4096. The 12 events were converted 

from the Saver file format to ASCII and imported into a software program called DADiSP, a 

product of DSP Development Corp.,1 for further analysis. 

1

The mention of specific products or manufacturers does not imply endorsement by the National Institute 

for Occupational Safety and Health. 

The acceleration shocks for truck A are shown in figure 1 and for truck B in figure 2. 

Comparing the shocks on truck A with the shocks shown in figure 3 and operators’ written logs, 

the authors determined that shock events A1, A3, A5, and A6 were caused by loading. The other 

three shock events on truck A (A2, A4, and A7) and all shock events on truck B were caused by 

rough ground, as determined by comparing figure 4 and operators’ written logs. The average 

peak frequency of the shocks on the seat cushion in truck A was 35 Hz, and the average 

frequency of the “rough ground” shocks was 1.4 Hz. Interestingly, the average peak frequency 

of all truck B shocks was also 1.4 Hz. 
C

A
 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 8 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

0 1 2 3 4 5 6 7 

T ime (se c ) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

B
 

-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 5 6 7 8 

T ime (se c ) 

x - pedest al 

y - pedest al 

z - pedest al 

x - seat 

y - seat 

z - seat 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0
 

-0.5
 8
 

-1.0
 

-1.5
 

-2.0
 

-2.5
 

-3.0
 

-3.5
 

0 1 2 3 4 5 6 7 

Time (sec) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

D
 

-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 5 6 7 8 

T ime (se c ) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

Figure 1.—Truck A shock events. A, Loading event, A1; B, rough ground event, A2; C, loading event, A3; 

D, rough ground event, A4; E, loading event, A5; F, loading event, A6; G, rough ground event, A7. 
E
 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

F

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

G

8 

8 

-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 5 6 7 8 

T ime (se c ) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

0 1 2 3 4 5 6 7 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

0 1 2 3 4 5 6 7 

T ime (se c ) 

T ime (se c ) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

Figure 1.—Truck A shock events (continued). A, Loading event, A1; B, rough ground event, A2; C, loading 

event, A3; D, rough ground event, A4; E, loading event, A5; F, loading event, A6; G, rough ground event, 

A7. 
C

0 1 2 3 4 5 6 7 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

A

B

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

T ime (se c ) 

Time (sec) 

Time (sec) 

8 

8 

8 

0 1 2 3 4 5 6 7 

0 1 2 3 4 5 6 7 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

D

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

Time (sec) 

0 1 2 3 4 5 6 7 8 

Figure 2.—Truck B shock events. A, Event 1; B, event 2; C, event 3; D, event 4; E, event 5. 
E
 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0
 

-0.5
 8
 

-1.0
 

-1.5
 

-2.0
 

-2.5
 

-3.0
 

-3.5
 

0 1 2 3 4 5 6 7 

Time (sec) 

x - pedestal 

y - pedestal 

z - pedestal 

x - seat 

y - seat 

z - seat 

Figure 2.—Truck B shock events (continued). A, Event 1; B, event 2; C, event 3; D, event 4; E, event 5. 

-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 

Time (sec) 

Acceleration (G's) 

x - pedestal 

y - pedestal 

z - pedestal 

Figure 3.—Acceleration measured after dropping 1-1/2-ton rock from a height of 10 ft onto the bed of a 

haulage truck. 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

0 1 2 3 4 

Time (sec) 

Acceleration (G's) 

x - pedestal 

y - pedestal 

z - pedestal 

Figure 4.—Acceleration when truck hit in the side by a shovel. 
GPS-ACCELERATION STUDIES 

A typical epidemiological study involves recording when and where people react to a hazard 

and plotting the results on a map. To determine the frequency and causes of jolting and jarring, 

it is necessary to determine when and where these shocks occur, so establishing a relationship 

between jolt occurrence and location is important. A system that ties acceleration data with 

Global Positioning System (GPS) data was developed, assembled, and tested to provide an 

imprint of the jolts on a mine map (figure 5). This information will be of value in providing 

feedback to truck operators about how their driving affects jolting and jarring and identifying just 

where haulage road problems are. 

Figure 5.—GPS-acceleration data system 

Many verbal reports are available from truck drivers concerning where and how they received 

injuries while driving, but no way has been available until recently to establish where these 

injuries occurred. However, recent experiments by SRL researchers [2] indicate it may be 

feasible to mount an accelerometer on the frame of a truck. The accelerometer would send 

signals to GPS hardware. When the truck is jolted or jarred, the shock would appear on the mine 

dispatcher’s screen in real time. When groups of jolts are seen on the screen, corrective actions 

could be taken. One such action might be to provide information to a shovel operator that he or 

she is loading the trucks in a manner that jolts the operator. Or the haulage road in that area could 

be resurfaced. The GPS could lead to refining information about what conditions most frequently 

cause or contribute to jolting and jarring. Investigations continue on what software components 

could allow the display of jolts on a computerized mine map in real time. 

The output of the initial SRL experiment was an ASCII computer file containing the location 

of every jarring event over 2 g’s (the minimum threshold the instrument could measure) over the 

time of the test. Although the truck traveled large sections of the mine without an event over the 

2-g threshold, a group of events was recorded for an inclined section of the haulage road. 

Because the internal frequency filter of the GPS was set at 1000 Hz and the filter of the Dallas 

Instrument Saver was set at 200 Hz, many more events were recorded per hour using the GPS 

than were recorded using the Saver. 

Using the mine’s GPS data, shock events A1 through A6 were plotted onto a mine map 
(figure 6). These shocks occurred around an area of the mine where the trucks were being loaded. 

However, shocks A2, A4, A7, and B1 through B5 were caused by rough ground. A better 

analysis could be made if the locations of the shovels relative to the jolts and jars were known. 

Figure 6.—Shock events A1-A6 plotted on mine map 

FIELD TESTS AT CATERPILLAR PROVING GROUNDS 

Three sets of experiments were set up at Caterpillar, Inc.’s, proving grounds in Green Valley, 

AZ. The instruments in the three tests were the same as those used to collect data at the mine. The 

set-up parameters were threshold level, 1 g; filter frequency, 100 Hz; range, ±20 g’s; samples per 

second, 512; recording time, 4 sec; and samples per event, 2048. 

In the first test, a large rock was dropped into the bed of a Caterpillar truck from over 10 ft above 

the bed surface. The drop produced a distinctive curve (figure 3) in which a significant jolt was 

registered in the z-direction when the rock struck the truck bed. In the second test, the truck was hit 

from the side by a loading shovel (figure 4). To measure the magnitude of individual jolts under 

controlled circumstances, a third experiment was designed that involved a course (dirt road) with 

a series of bumps positioned randomly along the course. A truck was driven along the course at 5 

mph. Figure 7 shows an empty truck going over a bump, while figure 8 shows the same truck going 

over a bump loaded. 

The curve shown in figure 3 was subsequently recognized in the event curves generated at the 

mine, but the signature of the side hit by the shovel (figure 4) was not. The authors suggest that 

when these side hits do occur, they put the spine in a vulnerable alignment for any following shock. 
-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 

Time (sec) 

Acceleration (G's) 

x - pedestal 

y - pedestal 

z - pedestal 

Figure 7—Accelerations on truck going over course empty. 

-3.5 

-3.0 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 1 2 3 4 

Tim e (se c) 

Acceleration (G's) 

x - pedes tal 

y - pedes tal 

z - pedes tal 

Figure 8—Accelerations on truck going over course loaded. 

Dr. David Wilder,2 director of the Vibration and Seating Laboratory, Lower Spine Research Center 

of the University of Iowa, has provided extensive data to this project on what combination of jolts 

is likely to harm a truck operator. His hypothesis, which he calls the “double-strike effect,” suggests 

that the first jolt sets up the back for the second jolt, and it is that second jolt which could injure the 

back. 

2

N.B. Fethke, D.G. Wilder, and K. Spratt. “Seated Trunk Muscle Response To Impact.” Accepted for 

presentation at the International Society for the Study of the Lumbar Spine, April 9-13, 2000, Adelaide, Australia. 

CONCLUSIONS 

1. Rough ground and loading were the primary causes of the jolting and jarring events recorded 
at the surface mine. Jolting and jarring caused by dumping did not appear in the events recorded. 

2. Jolting and jarring from loading were more frequently recorded on truck A than on truck B, but 

there were no statistically significant differences in the trucks. 

3. The double-strike effect, where the first jolt sets up the driver for injury by a second jolt, was 

not seen in the mine data. However, the possibility of its occurrence is evident in the rock drop 

experiment. 

4. GPS can be used as an epidemiological tool for studying and characterizing jolting and jarring. 

REFERENCES 

[1] International Standards Organization. 1997. Mechanical Vibration and Shock. Evaluation of 

Human Exposure to Whole-Body Vibration, Part 1: General Requirements, ISO 2631-1:1997(E). 

[2] Miller, R., and others. 1999. Tying Acceleration and GPS Location Data To Create a Mine 

Management Tool. Presentation SME ann. meeting, Denver, CO, Preprint 99-118.