RI 9652 REPORT OF INVESTIGATIONS/2000

Test Results of Collision Warning Systems

for Surface Mining Dump Trucks

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Report of Investigations 9652

Test Results of Collision Warning Systems

for Surface Mining Dump Trucks

By Todd M. Ruff

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Pittsburgh Research Laboratory

Pittsburgh, PA

May 2000
International Standard Serial Number

ISSN 1066-5552
CONTENTS

Page

Abstract ........................................................................................ 1

Introduction ..................................................................................... 2

Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of technologies tested ..................................................................... 3

Radar systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Radio-frequency identification systems ............................................................... 4

Test description .................................................................................. 5

Test results (OTS systems) .......................................................................... 8

System 1—Radar Backup Alarm System 201 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

System 2—Ogden Intelligent Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

System 3—Guardian Alert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

System 4—Mintronics Body Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

System 5—Nautilus Buddy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Test results (prototype systems) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

System 6—Ultrawide-band radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

System 7—ID International, RFID system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

System 8—Pittsburgh Research Laboratory HASARD system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Radar systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Radio-frequency identification systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Appendix A: Collision warning system test description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

ILLUSTRATIONS

1. Fatal accidents in metal/nonmetal mining by classification ............................................. 2

2. FMCW radar-based collision warning system manufactured by Ogden Safety Systems showing antenna and 

electronics enclosure and alarm display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3. Prototype RFID-based collision warning system built by ID International .................................. 4

4. Komatsu 210M 50-ton-capacity dump truck used as test platform ....................................... 5

5. Komatsu 210M, rear view ..................................................................... 6

6. Test configuration using pickup as obstacle ....................................................... 6

7. Test configuration using person as obstacle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8. Cinder block test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9. Doppler radar system manufactured by R. F. Knapp showing antenna and processing electronics and alarm

 display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

10. Test results for Knapp System 201, narrow beam, and person .......................................... 9

11. Test results for Knapp System 201, wide beam, and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

12. Test results for Knapp System 201, wide beam, and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

13. Test results for Knapp System 201, wide beam, and pickup perpendicular to dump truck . . . . . . . . . . . . . . . . . . . . . . 13

14. Test results for Knapp System 201, wide beam, and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

15. Detection zone for Knapp System 201, wide beam, and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

16. Detection zone for Knapp System 201, wide beam, and pickup perpendicular to dump truck . . . . . . . . . . . . . . . . . . . 16

17. Test results for Ogden Intelligent Radar and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

18. Test results for Ogden Intelligent Radar and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

19. Test results for Ogden Intelligent Radar and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

20. Detection zone for Ogden Intelligent Radar and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

21. Guardian Alert radar system showing antenna and electronics enclosure and alarm display . . . . . . . . . . . . . . . . . . . . . 22

22. Test results for Guardian Alert radar and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

23. Test results for Guardian Alert radar and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

cm centimeter MHz megahertz

dB decibel mi/h mile per hour

ft foot ms millisecond

in inch mW milliwatt

kHz kilohertz ns nanosecond

km/h kilometer per hour V volt

m meter ° degree

ILLUSTRATIONS—Continued

Page

24. Test results for Guardian Alert radar and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

25. Detection zone for Guardian Alert radar and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

26. Body Guard tag reader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

27. Body Guard tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

28. Test results for Body Guard and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

29. Test results for Body Guard and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

30. Test results for Body Guard and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

31. Detection zone for Body Guard and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

32. Test results for Buddy system and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

33. Prototype radar system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

34. Test results for Multispectral ultrawide-band radar prototype and person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

35. Detection zone for Multispectral ultrawide-band radar prototype and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

36. Prototype ID International tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

37. Test results for PRL’s HASARD system and pickup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

A-1. Example of size of detection zones for sensors mounted on front bumper and rear axle of off-road dump truck . . . . . 42

A-2. Fifty-ton-capacity Komatsu dump truck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

A-3. Mounting positions for RFID sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

TABLES

1. Fatalities involving crushing by mobile equipment ................................................... 2
TEST RESULTS OF COLLISION WARNING SYSTEMS

FOR SURFACE MINING DUMP TRUCKS

By Todd M. Ruff1

ABSTRACT

An average of 13 mine workers are killed each year by being run over or pinned by mobile mining equipment.

At surface mines, these accidents commonly involve large dump trucks that drive over a smaller vehicle or a

person that is in the dump truck’s blind spot. One method of detecting a person or another vehicle in a blind spot

is to use some type of sensor technology such as radar or radio-frequency identification (RFID). Researchers

at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health tested a number

of commercially available and experimental sensors that monitor obstacles in a vehicle’s blind spots. None of

the sensors had been previously applied to the specific problem of rigid-frame surface mining trucks. This report

documents the procedures and results of tests conducted after RFID and radar systems were mounted on a 50-toncapacity dump truck. It was determined that both RFID and radar technology show promise for detecting

obstacles in the blind spots of mining equipment; however, more development work is needed to meet the unique

requirements of mining equipment and the mine environment.

1

Electrical engineer, Spokane Research Laboratory, National Institute for Occupational Safety and Health, Spokane, WA.
2

Figure 1.–Fatal accidents in metal/nonmetal mining by classification. (Source: MSHA)

INTRODUCTION

For the 5-year period between 1994 and 1998, powered

haulage accounted for the majority of fatal accidents in

metal/nonmetal mines (table 1; figure 1). According to the Mine

Safety and Health Administration (MSHA 1999), approximately

20% of these fatalities involved the off-road dump trucks used in

surface mining. 

In 1998, 13 miners were killed in metal/nonmetal and coal

mines when they were run over or pinned by mobile equipment.

An average of 13 workers were killed per year in such types of

accidents in the previous 3 years also. Over half of these accidents could have been avoided if the equipment operator had

been adequately warned of an impending collision (table 1).

Many of these avoidable accidents involved dump trucks that ran

over a worker or a small vehicle hidden from view in the blind

spot of the truck. Despite the requirement for audible

backup alarms, these accidents are still occurring with unsettling

frequency. In fact, at the time of this report, MSHA was

considering regulations that would require the use of some type

of blind spot sensor (30 CFR Parts 56, 57, 77, 1998).

Researchers at the Spokane Research Laboratory (SRL) of

the National Institute for Occupational Safety and Health

(NIOSH) are investigating sensor technologies that can be used

to detect the presence of an obstacle in the blind spot of a piece

of mining equipment and provide a warning to the equipment

operator. A preliminary analysis indicated that such technology

is available and is being used in other industries. However, applying these technologies to off-road dump trucks and other

mining equipment has proven to be more of a challenge than first

expected.

Table 1.—Fatalities involving crushing by mobile equipment

Year Total no. of fatalities (figures do not include

rollovers)

No. of fatalities that could have been avoided

using collision warning system.

1998 . . . . . . . . . . . . 13 6

1997 ............ 97

1996 ............ 15 8

1995 . . . . . . . . . . . . 16 9

Source: MSHA Fatal Alert Bulletins (http://www.msha.gov)

APPROACH 
3

Figure 2.–FMCW radar-based collision warning system

manufactured by Ogden Safety Systems showing antenna and

electronic enclosure (left) and alarm display (right).

A collision warning system consists of some type of sensor

that detects the presence of an object, an interface that provides

an audible and/or visual alarm to the equipment operator, and

wiring between the two. Potential sensor technologies include

ultrasonic echo detection, infrared reflection, radar (radio detection and ranging), video cameras, and radio-frequency identification (RFID) systems. 

A product search was conducted to determine the

availability of collision warning systems that could be applied

to the mining problem. We found many systems being used on

long-haul trucks, passenger cars, light trucks, vans, buses, and to

a limited extent, construction equipment. A few foreign systems

are specifically manufactured for mining equipment.

Next, SRL researchers talked with mining personnel,

equipment manufacturers, and engineers at MSHA to determine

why existing collision warning systems are not being used

extensively by the mining industry. They indicated that the main

factors are (1) lack of field testing and research to determine the

effectiveness of these systems, (2) poor reliability because of

high false alarm rates, and (3) poor reliability and high

maintenance because of the harsh mining environment. Based on

this information, researchers decided that further product

development and extensive field tests were needed before

collision warning systems would be widely embraced.

The next step was to narrow the selection of the collision

warning systems to those that showed promise for surface

mining applications. While other technologies are available, such

as infrared, ultrasonic, and video, the evaluations were limited

to radio-frequency devices (radar and RFID). This decision was

based on earlier research [Johnson et al. 1986] and experience.

Radio-frequency devices are more robust and can handle the

harsh conditions of surface mining. They are not affected by

adverse weather, heat or sunlight, dust, or moderate amounts of

dirt and mud buildup on the sensor. The other technologies may

be able to address the particular challenges of surface mining as

they are improved, but for this study, only radio-frequency

devices were tested.

Five off-the-shelf (OTS) systems were purchased or

borrowed for evaluation at SRL. Two more prototype systems

were developed under contract as alternatives to OTS systems.

Another prototype system being developed for underground coal

mining was also evaluated. Four of the systems are based on

radar technology, and four are based on RFID. 

Preliminary tests of these systems in the lab showed the need

for testing each system on actual mining machines. Moving parts

and the amount of steel present on large mining equipment may

have detrimental effects on the operation of a collision warning

system. The only way to ensure that a system operates reliably

is to mount it on the actual machine and under actual operating

conditions.

DESCRIPTION OF TECHNOLOGIES TESTED

RADAR SYSTEMS

Radar technology is one of the most established methods of

obstacle detection. Many types of radar are used in collision

warning systems, including pulsed or ultrawide-band, Doppler,

and frequency-modulated continuous wave (FMCW). Most

operate in the microwave frequencies within the C, X, or K

bands. Some of the newer systems for highway applications

operate at even higher frequencies. 

A radar system operates by emitting electromagnetic energy

and detecting this energy when it is reflected from an object or

target. Information about the target, such as range and direction

of movement, can be acquired by analyzing this reflected energy

[Skolnik 1990]. The technology is well suited to collision

avoidance applications because it is not affected by rain, snow,

dust, or even a moderate buildup of mud on the antennas.

Many collision warning systems are based on radar

technology. The systems consist of a radar antenna(s), processing electronics, and an operator interface or alarm display

(figure 2). The radar unit is mounted on the vehicle and directed

toward the area to be monitored. If an object of sufficient crosssectional area is within the beam pattern of the radar

antenna, the signal is reflected to the unit and is processed. If

certain criteria are met, an alarm is generated. The type of alarm

varies with the type of display. 
4

Figure 3.–Prototype RFID-based collision warning system

built by ID International.

 The most common type of radar used in collision warning

systems employs Doppler shift detection. These systems only

detect relative movement of objects by sensing a frequency shift

in the reflected signal. For the system to activate an alarm, either

the object within the transmitted beam pattern must move toward

the stationary vehicle, or the vehicle must move toward the

object. If both object and vehicle are not moving, no alarm is

activated. This has the advantage of providing alarms only

when a vehicle is moving and a collision is imminent. However,

it has the disadvantage of not providing an alarm that allows

sufficient time to stop if a stationary object is very close to a

vehicle that starts moving. Other types of radar, such as FMCW,

can be configured to operate in this manner also.

Pulsed radar is also used for collision warning systems.

Because of the pulsed nature of the output signal, the average

power output by the radar is extremely low (microwatts). Also,

time of flight for the reflected signal is easily measured, and

accurate range information can be provided as long as the detected object is not immediately next to the antennas. Systems

using this type of radar can sense the presence of an object

whether there is relative motion or not. 

RADIO-FREQUENCY IDENTIFICATION SYSTEMS2

Several companies have applied RFID systems to the

collision avoidance problem. The systems typically consist of

a tag reader, tags, and an operator interface or alarm display

(figure 3). The tag reader detects radio transmissions from a tag

if the tag is within its reading range. The tag reader is mounted

on the mine equipment, while tags are mounted on any item that

is to be avoided. These items can include other vehicles, pedestrian workers, power and utility poles, or even a building. The

small cost and small size of most tags allows them to be mounted

on hard hats, personnel belts, or anywhere on the exterior of a

vehicle. The nature of radio-frequency signals makes this

technology ideal for harsh environments because radio

transmissions are not adversely affected by harsh weather, dust,

or moderate amounts of mud buildup on the antennas. However,

radio signals can be affected by interference from multipath

effects and other radio signal sources.

2

RFID can also be referred to as radio signal detection. Traditional RFID uses

transmission of digital codes for identification functions. Digital codes may or may not

be implemented in collision avoidance applications. Only the detection of the correct

radio signal is required.

There are two types of tags: passive and active. Each has

advantages and disadvantages. For passive tags, the tag reader

constantly transmits a signal that activates a tag if it is within

range. The tag then answers with a unique signal that is detected

by the tag reader. The advantages of passive tags are that there

is no requirement for external power, they need little

maintenance, and they are very inexpensive. The disadvantage

is that they often have a more limited reading range than active

tags.

With active tags, the reader can be passive and just listen for

the unique transmissions from the tag. The tag usually transmits

constantly and requires external power. The advantages of these

tags is an increased reading range and more functionality. The

disadvantages include the need for batteries and increased cost

and size when compared to passive tags.

If a reader detects a tag within its reading range, signal

processing software analyzes the signal to determine signal

strength and integrity. If the acquired signal meets alarm criteria,

then an audible and/or visual alarm is indicated at the alarm

display. The alarm thus warns an operator that a tag is in

proximity to the equipment.

At least three companies are currently working on RFID

systems for collision avoidance in mines. Two of these companies have OTS systems available for remote-controlled

equipment (mainly load-haul-dump units, or LHD’s) used in

underground mines. All three companies were in the process of

developing a system for surface mine haulage trucks when this

report was published. 
5

Figure 4.–Komatsu 210M 50-ton-capacity dump truck used as test platform.

TEST DESCRIPTION

Tests of the collision warning systems were designed based

on experience gained from previous tests, some aspects of SAE

J1741 Discriminating Backup Alarm Standard [Society for

Automotive Engineers (SAE) 1998], and guidance from MSHA.

A detailed test description is found in appendix A. The systems

were to be tested on a rigid-frame, off-road dump truck that

represented those used in industry as closely as possible.

Because of the number of systems to be tested and the amount of

time required, the tests could not be conducted at an operating

mine. Therefore, a dump truck was rented, and the tests were

c o nd uc ted at a remote auxiliary site o f S RL.

The largest dump truck available for rental in the Spokane

area was a 50-ton-capacity Komatsu 210M Haulpak3

 (figures 4

and 5). Unfortunately, although this truck has similar features and

is commonly used in sand and gravel operations, it is smaller

than most trucks used in surface mining, where 190- or 240-ton

trucks are common. While not an ideal representation of the

larger trucks, the 50-ton truck did provide an adequate platform

for the tests.

Each collision warning system was mounted on the truck

according to the manufacturer’s suggestions and with the

requirement that the sensor be accessible and unobtrusive during

the truck’s operation. To monitor the rear blind spot of the truck,

the sensor was mounted near the light bar above the rear axle. To

monitor the front blind spot, the sensor was mounted near the

front bumper or on the grill.

3

Mention of specific products or manufacturers does not imply endorsement by

the National Institute for Occupational Safety and Health.

The test area was approximately 61 m long by 30 m wide

(200 by 100 ft). It was cleared of debris and graded flat. The

surface of the test area was dirt and gravel with no large rocks or

ruts. This gave researchers a clear field for testing the collision

warning systems under ideal conditions. Obstacles and other

debris were then added as each test progressed. 

The obstacles to be detected by the collision warning system

consisted of either a person or a pickup truck. Two scenarios

were tested for each obstacle: (1) the dump truck was driven

toward the stationary obstacle and (2) the obstacle moved toward

the stationary dump truck (figures 6 and 7). A detection zone was

then recorded that showed in which areas the obstacle was

consistently detected and an alarm was sounded. When needed,

a second zone was recorded that indicated the area in which an

obstacle was detected sporadically, i.e., less than 100% of the

time but more than 10%. The detection zone was recorded by

placing the obstacle on the points of a grid at 76-cm (2.5-ft)

spacings in the dump truck’s blind spot. As the dump truck or

obstacle was moved, the state of the system’s alarm was noted

for each position.

The alarm display for each system was mounted near the

sensor or antennas. This allowed researchers to monitor the

alarm easily. Normally the alarm display would be mounted in

the cab with the operator.

It is critical that the audible alarm be easily distinguished

from all background engine noises and other warning buzzers.

Also, it is important that any lights or LED’s be visible in any

lighting condition. The alarm’s effectiveness in the cab was

not tested because most of the collision warning systems were

not designed for surface mining haulage equipment. Each
6

Figure 5.—Komatsu 210M, rear view.

Figure 6.—Test configuration using pickup as obstacle.

manufacturer will have to develop an appropriate alarm display

to meet the demands of this application. Guidelines for developing warning signals can be found in SAE J1741 and in U.S.

Department of Transportation reports [Harpster et al. 1996; Huey

et al. 1997].

According to SAE J1741, it is desirable that a collision

warning system ignore an object the size of a cinder block in the

blind spot of the dump truck (figure 8). While this may or may

not be important to a mine implementing a collision warning

system, researchers tested each OTS radar system to see how it

reacted to a cinder block. RFID-based systems were not tested

with the cinder block because the block would obviously be

ignored if no tag were attached to it.
7

Figure 7.–Test configuration using person as obstacle.

Figure 8.–Cinder block test.
8

Figure 9.–Doppler radar system manufactured by R. F.

Knapp showing antenna and processing electronics (left) and

alarm display (right).

TEST RESULTS (OTS SYSTEMS)

SYSTEM 1- RADAR BACKUP ALARM SYSTEM 201

Manufacturer:

R. F. Knapp Company, Spirit Lake, Idaho

Description:

The system uses microwave radar technology in which

Doppler shift is sensed. The antenna and processing electronics

are contained in a polyvinyl-chloride (PVC)-type plastic enclosure. The alarm display consists of a light and a buzzer, both of

which are simple on-off indicators. The system is shown in

figure 9.

Current Applications:

The system is currently used on construction equipment that

includes front-end loaders, cranes, and over-the-road trucks.

Rear Blind Spot Test Results:

The system was mounted on the rear of the dump truck in a

location 20 cm (8 in) in front of the light bar and just above the

axle at a height of 1.7 m (68 in) from the ground. The alarm

display was also mounted on the light bar so researchers could

easily monitor the state of the alarm. Normally the alarm display

would be located in the cab of the dump truck.

Two models were tested, a narrow-beam system and a

standard wide-beam system. The narrow-beam system did not

have wide enough coverage to detect a person immediately behind the outermost tires of the truck (figure 10A), so the widebeam sensor was used for the rest of the tests. The narrow-beam

sensor is more appropriate for narrower equipment, or two units

could be placed side-by-side for an even wider coverage area on

a larger truck [Boldt and Backer 1997].

The wide-beam radar system was mounted on the rear of the

truck in the same location as the narrow-beam system. However,

when the truck was moved, false alarms were set off when the

system detected the rotation of the truck’s tires. This problem

was solved by moving the radar unit another 25 cm

(10 in) away from the light bar so that the detection zone started

just beyond the tires (figure 11B). On a larger truck, there may

not be a mounting location with sufficient offset to allow the

radar unit to ignore tire rotation. Boldt and Backer [1997] note

this problem and possible solutions that involve installing multiple narrow-beam sensors.

The system was tested for false alarms in a clear field.

False alarms did occur if the radar unit was tilted downward too

far, and it was suspected that the radar unit was detecting the

ground. The angle of tilt needed to ignore the ground depends 

on the ground surface and its composition. In this situation, a

downward tilt of 5° or less was enough to eliminate false

alarms. Both the height of the radar unit and the angle of tilt

would have to be adjusted for ground conditions and each type of

equipment at a mine. There were also occasional false alarms

(usually just a single beep of the alarm display) from unknown

sources. According to Boldt and Backer, this also can be

eliminated by using higher mounting locations and adjusting the

radar unit’s tilt.

Figure 11A shows the results of tests with the wide-beam

sensor when a person was used as the obstacle. This system reliably detected a person in the recorded detection zone when the

truck moved toward the person or the person moved toward the

truck. However, there were occasional alarms when the distance

between the target and the radar unit was increased. Usually

with Doppler-based systems, an alarm is desired only when the

distance decreases because this is the dangerous situation. The

maximum distance that a person was detected was 6.9 m (22.5 ft)

when the range of the system was set at approximately 75%.

Range settings above this amount resulted in more false alarms.

Figure 12A shows test results when a pickup was used as the

obstacle. The "reliable detection zone" indicates the area in

which the pickup was detected consistently, i.e., if the front

bumper of the pickup was within the indicated zone, detection

was consistent. This test was conducted with the pickup facing

the rear of the dump truck, an orientation that resulted in the least

amount of cross-sectional area that could reflect radar energy.

The maximum distance over which the pickup was detected was

18.3 m (60 ft). The minimum distance occurred directly in front

of the radar. As seen in figure 12A, the rear of the pickup truck

was detected as long as it remained in front of the sensor,

accounting for the detection areas that extend down the sides of

the dump truck. In other words, if a pickup truck is parked so that

its front bumper is within this zone, it will be detected when the

dump truck moves.
9

Figure 10.–Test results for Knapp System 201, narrow beam, and person. A, Detection zone; B, mounting

position; C, rear view of truck.
10

Figure 11.–Test results for Knapp System 201, wide beam, and person. A, Detection zone; B, mounting

position; C, view behind truck.
11

Figure 12.–Test results for Knapp System 201, wide beam, and pickup. A, Detection zone; B, rear view of

truck; C, view behind truck.
12

The next set of tests, shown in figure 13, shows results when

the truck was rotated 90° or parallel to the back of the dump

truck. This position resulted in the maximum amount of crosssectional area, and an increase in detection range was seen. The

maximum distance was equal to 19.8 m (65 ft). Two scenarios

were tested. In the first, the pickup was driven through the radar

detection zone parallel to the back of the dump truck. In the

second, the pickup was parked and the dump truck was driven in

reverse. Both tests had similar results. The reliable detection

zone indicates the point where the pickup was detected. The

entire length of the pickup had to be contained in the zone

indicated.

One disadvantage with this system (and radar technology in

general) is that the maximum detection distance depends on the

size and material of the obstacle. A person is detected up to a

distance of 6.9 m (22.5 ft) and a truck to a distance of 19.8 m (65

ft). Large, flat metal objects are easily detected by radar, but

irregular-shaped objects with no metal or low water content are

not good reflectors of microwave energy and may only be

detected at close range.

Front Blind Spot Test Results:

The radar system was mounted level on the front of the dump

truck under the front bumper (figure 14B) at a height of 61 cm (2

ft) and tested in a clear field. No false alarms were produced as

the dump truck was driven forward.

Figure 14A shows the detection zone when a person was the

obstacle. The reliable detection zone extended to 6.9 m (22.5 ft).

Figure 15 shows the detection zone when a pickup, oriented

to face the dump truck, was the obstacle. The reliable detection

zone extended from the sides of the dump truck out to 19.8 m (65

ft). Figure 16 shows the detection zone when the pickup was

rotated 90°. In this case, the detection zone extended from the

front bumper of the dump truck out to 24.4 m (80 ft). This is a

dramatic example of the difference in the maximum detection

range (i.e., a difference of 17.5 m [57.5 ft]) depending on

whether a person or a pickup is being detected.

Cinder Block Test:

For this test, a standard 40- by 20- by 20-cm (16- by 8- by

8-in) concrete cinder block was laid on its side and put in the

path of the dump truck (figure 8). Both rear and front blind spots

were tested.

When the radar unit was mounted on the rear of the dump

truck at a height of 1.7 m. (68 in), the cinder block was detected

if it was placed 6 to 12 m (20 to 40 ft) from the radar unit and the

truck was driven in reverse. When the radar unit was mounted

under the front bumper at a height of 61 cm (2 ft), the cinder

block was detected 0 to 5 m (17 ft) away from the front of the

truck. Whether the cinder block was detected or not

depended on the radar’s mounting height and tilt. While the

mounting position could probably be adjusted so that the radar

unit would ignore the cinder block, its sensitivity to a person or

other obstacle would be decreased. 

SYSTEM 2 –OGDEN INTELLIGENT RADAR

Manufacturer:

Ogden Safety Systems, Brodsworth, Doncaster, U.K.

Description of System:

This microwave radar system transmits a low-power

 (5 mW) signal and measures reflections from objects within the

beam. It can calculate distance and relative speed of a detected

object.

The system is shown in figure 2 and consists of a radar antenna and an electronics enclosure, an alarm display, and wiring.

The alarm display is mounted in the equipment cab. It shows

three range gates that indicate distance to the obstacle. LED’s

flash red in the appropriate range to indicate the presence of an

obstacle. A beeper increases in frequency as the equipment gets

closer to the obstacle.

This system had not been used in the United States at the

time of this publication. It operates at a microwave frequency

that is not allocated for this purpose, and it is not approved by

Federal Communications Commission. The system may be approved for use in the United States at a later date.

Current Applications:

The system is used on front-end loaders at surface mines, 

quarries, and construction sites. It has also been used on articulated dump trucks.

Rear Blind Spot Test Results:

The system was mounted just below the light bar on the rear

of the truck at a height of 1.5 m (58 in) (figure 17B, C). The

electronics enclosure is mounted on a steel frame that can be

easily tilted. For these tests, the enclosure was mounted level.

For higher mounting positions, it may be necessary to adjust the

tilt to pick up objects shorter than the mounting height. The alarm

display was placed near the light bar so researchers could

monitor the alarm’s state. 

There are various options for configuring the range and

detection settings. Each of the three range gates indicated on the

alarm display can be set for a particular distance. Also, velocity

thresholds can be set to detect objects moving faster than 0.5 or

5 km/h (0.3 or 3.1 mi/h). For these tests, the range gate settings

were selected for the maximum total range of 9 m

(29.5 ft) and the slowest movements of 0.5 km/h (0.3 mi/h).
13

Figure 13.–Test results for Knapp System 201, wide beam, and pickup perpendicular to dump truck. A, Detection

zone; B, view behind truck.
14

Figure 14.–Test results for Knapp System 201, wide beam, and person. A, Detection zone; B, mounting

position; C, view in front of truck.
15

Figure 15.–Detection zone for Knapp System 201, wide beam, and pickup.
16

Figure 16.–Detection zone for Knapp System 201, wide beam, and pickup perpendicular to dump truck.
17

Figure 17.—Test results for Ogden Intelligent Radar and person. A, Detection zone; B, mounting position;

C, back view of mounting position.
18

The system was first tested in a clear field. The dump truck

was backed up several times, and the alarm state was noted. No

false alarms occurred with a clear field. The radar unit did not

detect the rotation of the tires even though it had been mounted as

far back as possible near the light bar.

Figure 17A shows the results of the tests when a person was

the obstacle. The reliable detection zone extended from near the

radar unit to approximately 6.4 m (21 ft). The same results were

obtained when either the person moved toward the stationary

dump truck or the truck was driven toward the person. The beam

width was sufficient to cover the area behind the dump truck’s

tires. However, the beam width may not be sufficient for larger

trucks. A “sporadic detection zone” was noted in which the

radar unit did not detect a person consistently. This zone was

quite small and on the fringes of the detection zone, so no

problems would result. 

Figure 18A shows test results when a pickup was the obstacle and faced the rear of the dump truck. If the front bumper

of the pickup was within the indicated zone, detection was

consistent to a maximum distance of 8.4 m (27.5 ft). The minimum distance occurred immediately in front of the sensor. 

Additional tests with the pickup oriented sideways were not

conducted with this or other systems because of time constraints.

Tests with the pickup facing the dump truck are believed to be

representative of a worst case (least amount of cross section) and

are sufficient to evaluate the performance of a collision warning

system. However, it is interesting to note the differences in

detection range for the different pickup orientations, as was seen

with the Knapp system.

These limited tests indicated that the Ogden radar unit does

not have a dramatic increase or decrease in detection range, depending on whether a pickup or a person is the obstacle. This is

an advantage in that the detection zone is well defined and

consistent with any obstacle. 

Front Blind Spot Test Results:

To test the front blind spot, the radar unit was mounted level

on the front bumper at a height of 76 cm (30 in), as shown in

figure 19B, C. The dump truck was driven forward in a clear

field, and no false alarms occurred.

Figure 19A shows the detection zone of the radar unit with

a person as the obstacle. The reliable detection zone extended

from about 76 cm (2.5 ft) away from the sensor out to 5.3 m (17.5

ft). A sporadic detection zone close to the radar unit was seen

with this configuration. This could be a problem in that a person

standing close to the bumper might or might not be detected as the

truck was driven forward from a stopped position.

Figure 20 shows the detection zone when the pickup was the

obstacle and oriented to face the dump truck. A small sporadic

detection zone was seen close to the bumper of the dump truck.

The reliable detection zone extended from the sides of the dump

truck out to 8.8 m (29 ft). As seen in figure 19, the

rear of the pickup truck was detected as long as it remained in

front of the sensor, accounting for the detection areas that extend

down the sides of the dump truck. 

Cinder Block Test:

The cinder block was not detected at any distance in the rear

blind spot tests, but it was detected at distances between 3 and

6 m (10 and 20 ft) in front of the dump truck. The lower

mounting height on the front bumper of the dump truck made the

radar unit more sensitive to smaller objects. Mounting the radar

unit at a higher position would eliminate detection of the cinder

block if desired.

SYSTEM 3 – GUARDIAN ALERT

Manufacturer:

Sense Technologies, Inc., Vancouver, BC, Canada

Description of System: 

This motion-sensing radar unit operates at 10.525 GHz,

which is a common frequency for police radar, intrusion alarms,

and door openers. The radar unit does not require on-site licensing and is protected under U.S. patents 4803488 and

5028920. 

The radar unit uses frequency modulation of the microwave

signal to determine the distance to an obstruction. The sensor is

also pulse modulated so that it will not activate radar detectors

or interfere with other similar devices. In fact, multiple sensors

may be used on the same vehicle. The sensor will alert the

operator to the nearest obstruction and, rather than requiring a

fixed time between the moment it first detects an obstruction, it

requires a fixed distance (12 cm [5 in]) in order to react. This

makes the sensor insensitive to the velocity of the vehicle and

simplifies the analysis.

The system is shown in figure 21 and consists of the radar

antenna and electronics enclosure, an alarm display, and wiring.

The alarm display is mounted in the cab and provides range gates

that indicate distance to the obstacle. Red, yellow, and green

LED’s flash to indicate an obstacle in a particular range gate, and

a beeper increases in frequency as the obstacle gets closer to the

equipment. This particular model was configured for three range

gates: 0 to 3, 3 to 6, and 6 to 12 m (0 to 10, 10 to 20, and 20 to

40 ft). The total range, beam width, and range gates can be

configured at the factory.

Current Applications: 

The system is used on passenger cars, light trucks, and

delivery vans.
19

Figure 18.—Test results for Ogden Intelligent Radar and pickup. A, Detection zone; B, mounting position;

C, view behind truck.
20

Figure 19.—Test results for Ogden Intelligent Radar and person. A, Detection zone; B, mounting position; C,

side view of mounting position.
21

Figure 20.—Detection zone for Ogden Intelligent Radar and pickup.
22

Figure 21.—Guardian Alert radar system showing antenna and

electronics enclosure (bottom) and alarm display (top).

Rear Blind Spot Test Results: 

The radar unit was mounted just below the light bar on the

rear of the truck at a height of 1.7 m (68 in) (figure 22B, C). For

these tests, the enclosure was mounted level, and the alarm

display was placed near the light bar so researchers could

monitor the alarm’s state.

Previous tests on heavy mining equipment showed that the

Guardian Alert radar unit malfunctioned because of equipment

vibration. In an attempt to dampen the vibration, rubber vibration

isolating grommets were used; on some mining equipment the

grommets helped, but on others they did not. On the Komatsu

dump truck, the grommets sufficiently dampened any errorcausing vibration. Because vibration seemed to depend on the

particular piece of mining equipment, the need for vibration

isolation would have to be determined during installation of the

radar unit.

The system was first tested in a clear field. The dump truck

was backed up several times, and the alarm state was noted. An

occasional, short-duration (single beep), false alarm occurred in

a clear field, but the source could not be determined. The radar

unit did not detect the rotation of the tires even though it was

mounted as far back as possible near the light bar. On a larger

truck, the tires might be detected, and an alternative mounting

configuration would be required.

Figure 22A shows the results of the tests when a person was

the obstacle. The reliable detection zone extended from near the

radar unit to 7.6 m (25 ft). The same results were obtained when

either the person moved toward the stationary dump truck or the

truck was driven toward the person. The beam width was

sufficient to cover behind the dump truck’s tires and beyond.

Figure 22A also shows three internal zones that are the range

gates of the alarm display within the reliable detection zone.

When an obstacle is within zone 1, the first range gate is

indicated by flashing LED’s and the buzzer. In zone 2, the

second range gate is indicated by different LED’s and a higher

frequency buzzer, and so on.

Figure 23A shows test results when the pickup was facing

the rear of the dump truck. If the front bumper of the pickup was

within the indicated zone, detection was consistent. The

maximum distance over which the pickup was detected was

13.7 m (45 ft). The minimum distance occurred immediately in

front of the sensor. As seen in figure 23A, the rear of the pickup

truck was detected as long as it remained in front of the sensor,

accounting for the detection areas that extend down the sides of

the dump truck. 

Front Blind Spot Test Results:

To test the front blind spot, the radar unit was mounted level

above the front bumper at a height of 1.2 m (48 in), as shown in

figure 24B. The dump truck was driven forward in a clear field,

and again an occasional, short-duration false alarm was set off.

Figure 24A shows the detection zone of the radar unit when

a person was the obstacle. The reliable detection zone extended

from the truck’s bumper out to 9.1 m (30 ft). The alarm display

range gates are indicated by zones 1, 2, and 3.

Figure 25 shows the detection zone of the radar unit when

the pickup was the obstacle and was oriented to face the dump

truck. The reliable detection zone extended from the sides of the

dump truck out to 11.4 m (37.5 ft). 

Cinder Block Test:

The cinder block was detected at both the front and the rear

at distances between 1.5 and 6.1 m (5 and 20 ft). The angle or

tilt of the sensor was adjusted to approximately 10° pointing upward. The cinder block was detected with this configuration

also. This radar unit has a 45° beam width in the vertical direction, so detection of the cinder block was expected. 

SYSTEM 4 – MINTRONICS BODY GUARD

Manufacturer : 

Mintronics Systems Corp., North Bay, ON, Canada

Description of System: 

This system is classified as an RFID-based system. The tag

reader consists of three separate enclosures: the processing

electronics, the transmitting antenna, and the receiver antenna

(figure 26). The transmitter constantly transmits a signal in the

UHF band. The tags are passive and therefore do not require external power (figure 27). If a tag is within range of the transmitter, it receives the signal, doubles it, and transmits it back to

the tag reader, which processes it to determine if the signal

strength is such that an alarm should be generated. 

The existing alarm display is an on/off-type alarm that

provides both audible and visual signals.
23

Figure 22.—Test results for Guardian Alert radar and person. A, Detection zone; B, mounting position; C,

view behind truck.
24

Figure 23.—Test results for Guardian Alert radar and pickup. A, Detection zone; B, view

behind truck.
25

Figure 24.—Test results for Guardian Alert radar and person. A, Detection zone; B, mounting position.

Figure 25.—Detection zone for Guardian Alert radar and pickup. 
26
27

Figure 26.—Body Guard tag reader.

Figure 27.—Body Guard tags.
28

Current Applications: 

The system is used in underground mines on remotecontrolled LHD units. The system automatically stops the

equipment if it gets too close to the remote-control operator.

Rear Blind Spot Test Results: 

The transceiver unit or tag reader was mounted near the light

bar on the rear of the truck at a height of 1.7 m (66 in) (figure 26).

Because this system was a demonstration unit, the alarm display

was integral to the tag reader enclosure. The receiver and

transmitter antennas were in separate enclosures and on opposite

sides of the tag reader enclosure. Extendable arms allowed the

antennas to be separated by approximately

2 m (6.5 ft), which was about half the possible travel space. For

permanent installations, the extendable arms are not needed, and

the antennas would be attached to the dump truck at spacings to

be determined by trial and error to optimize the detection zone.

The electronics enclosure could be installed in a protected place

inside the truck. 

Two tags were mounted on the hard hat of the person acting

as the obstacle (figure 27). While two tags were adequate for

our tests, Mintronics recommends that a minimum of three tags be

attached to the hard hat. This ensures that at least one tag will

pick up and return a signal at any orientation. Figure 28A shows

the results of the tests when a person was the obstacle. The

reliable detection zone extended from near the tag reader to 7.6

m (25 ft) away from the back of the dump truck. The same results

were obtained when either the person moved toward the

stationary dump truck or the truck was driven toward the person.

The zone shown is a bit skewed, covering the left side of the

truck more effectively than the right. This might be corrected by

adjusting the position of the antennas. 

A region in which a person was not detected 100% of the

time extended to 13.7 m (45 ft) outside the reliable detection

zone. However, if the person or dump truck moved approximately 61 to 152 cm (2 to 5 ft), the person was detected,

indicating that the area had signal nulls caused by multipath

interference. Because this sporadic detection zone is, for the

most part, on the outer edge of the reliable detection zone, intermittent detection would not be a detriment. However, an

occasional alarm would be generated from objects out as far as

13.7 m (45 ft), which might not be desirable if the dump truck

operator did not want alarms from tagged objects outside the

reliable detection zone. 

The detection range of this system is adjustable. Earlier

tests showed a trade-off between increased range and an increase

in the size of the sporadic detection zone. With a range setting of

approximately one-half full scale, the reliable detection zone was

adequate for this dump truck, and the sporadic detection zone’s

range was kept to a minimum. No false alarms occurred when

the tags were kept outside of both zones. 

Figure 29A shows test results when a pickup was the

obstacle. Two location schemes for the tags were tested. The

first was to place two tags on the antenna of the pickup. The

second was to place one tag on a plastic portion of the front

bumper and the other one on the hood of the truck in an

orthogonal direction to the first tag after mounting it on a piece of

plastic. Both locations produced similar results. It is suspected

that the detection zone could be lengthened by optimizing the

location of the tags, providing better plastic insulators for the

tags, and increasing the number of tags on the pickup. According

to the manufacturer, five or more tags with plastic insulators

should be mounted around the pickup.

This test was conducted with the pickup facing the rear of

the dump truck, as shown in figure 29B. If the front bumper of the

pickup was within the indicated zone, detection was reliable.

The maximum distance over which the pickup was detected was

6.1 m (20 ft). No sporadic detection region was seen in this test.

Front Blind Spot Test Results:

To test the front blind spot, the tag reader was mounted

above the front bumper at a height of 1.2 m (4 ft), as shown in

figure 30B. The extendable arms had sufficient clearance to be

extended to their full travel length, providing maximum

separation between the receiver and the transmitter. Range was

set to one-half.

Figure 30A shows the detection zone when a person was the

obstacle. Tags were mounted on the hard hat as in previous tests.

The reliable detection zone extended from the truck’s bumper out

to 7.6 m (25 ft). The sporadic detection zone extended to a

maximum of 11.4 m (37.5 ft).

Figure 31 shows the detection zone when the pickup was the

obstacle. Tags were placed on the front bumper and hood of the

pickup, and the pickup was oriented to face the dump truck. The

reliable detection zone extended from the bumper of the dump

truck out to 5.3 m (17.5 ft). Again, no sporadic detection zone

was seen.

SYSTEM 5 – NAUTILUS BUDDY SYSTEM

Manufacturer : 

Nautilus International Control and Engineering, Ltd.,

Burnaby, BC, Canada

Description of System:

This system is classified as an RFID-based system. The tag

reader consists of processing electronics and a loop antenna

(figure 32B, C). It was mounted on the front deck of the dump

truck, where it continuously transmitted a low-frequency signal

that encompassed the entire truck. Only one loop antenna was

needed to detect tags in blind spots at both the front and rear of
29

Figure 28.—Test results for Body Guard and person. A, Detection zone;

B, mounting position.
30

Figure 29.—Test results for Body Guard and pickup. A, Detection zone; B, view behind truck.
31

Figure 30.—Test results for Body Guard and person. A, Detection zone; B, view in front of truck.
32

Figure 31.–Detection zone for Body Guard and pickup.

the dump truck, although more antennas can be integrated into the

system to determine in which blind spot the tag is located. The

processing electronics also contain a separate high-frequency

transceiver to communicate with the tags.

The tag tested on this system is considered active. It is contained in a remote-control pendant manufactured by Nautilus that

is used in its radio-remote-control systems. Stand-alone tags are

being developed at this time. Each tag contains a transceiver to

communicate with the reader’s processing electronics. The tag

measures the field strength of the low-frequency signal generated

by the loop antenna. The field strength increases as the distance

between the tag and the loop antenna decreases. If

the field strength exceeds a user-defined limit, this information

is sent to the tag reader and an alarm is generated. On the system

tested, the alarm state was normally used to set the brakes of the

machine automatically. An alarm display for the dump truck

operator is under development.

Current Applications: 

The system is used in underground mines on remotecontrolled LHD’s and trucks. The Buddy system automatically

stops the equipment if it gets too close to the remote-control

operator.
33

Figure 32.—Test results for Buddy system and person. A, Detection zone; B, loop antenna; C, front view of

truck.
34

Blind Spot Test Results:

 The front and rear of the truck were tested simultaneously.

The tag reader was mounted on the front deck of the truck, next to

the cab, at a height of 3 m (10 ft) (figure 32C). Because the unit

tested was a demonstration unit, the alarm display was integral to

the remote-control pendant, and the alarm state was monitored

from the pendant.

The size of the detection zone is set by inputting the desired

detection radius. The field strength measured at this radius is then

saved as the alarm threshold. As the tag is moved around the

dump truck, the field strength is measured. Values of field

strength above the alarm threshold trigger an alarm whereas

values below this threshold do not. 

The tests involved a person walking around the dump truck

while holding the remote-control pendant containing the tag. The

oval pattern shown in figure 32A demonstrates the detection zone

with a setting of 18 m (59 ft) for the detection radius. The

actual detection zone extended 13.7 m (45 ft) from the front

bumper, 7.6 m (25 ft) from the rear wheels, and 9.1 m (30 ft) from

both sides. Note that the detection zone was larger in front of the

truck than in the rear because of the forward position of the

antenna. The detection zone can be adjusted using software to

eliminate this offset, or it can be altered to compensate for forward or reverse movement of the truck. By adding an antenna at

the rear of the machine, the position of the tag can also be determined, but this option is not yet available.

No sporadic detection zones or dead spots were seen near the

truck. The tag was even detected underneath the chassis of the

truck and in the wheel wells. No false alarms occurred when the

tag was outside the detection zone.

No tests were conducted with a pickup because of the way

the tag was packaged. Such tests should be conducted when a

stand-alone tag is available in order to find the best mounting

location for the tag.

TEST RESULTS (PROTOTYPE SYSTEMS)

Because of the initial difficulties in applying OTS collision

warning systems to surface mine haulage trucks, NIOSH contracted out the development of two new systems specifically

meant for mining equipment. This effort paralleled the testing of

OTS systems to provide an alternative technology if needed.

Another system currently being developed for continuous miners

in underground coal mines was also tested. 

SYSTEM 6 – ULTRAWIDE-BAND RADAR

Developer: 

Multispectral Solutions, Inc. (MSSI), Gaithersburg, MD

Description of System (Fontana et al. 1998): 

MSSI’s radar system is based on ultrawide-band technology

that uses nanosecond radar signal pulses to produce a wide, instantaneous bandwidth waveform. The radio frequency circuitry

for a ultrawide-band system is minimal, consisting of a low-noise

amplifier and broadband tunnel detector. In addition, most

ultrawide-band system designs are digital, further lending to lowcost modular designs and small-sized packages.

A transmitter module emits ultrawide-band radar pulses at a

fixed repetition rate from the transmitting antenna. A receiver

antenna picks up both the transmitted pulse and pulses reflected

from the environment and/or targets of interest. A radiofrequency module amplifies and filters the pulses and sends them

to a processing board. The transmitted pulse is picked up by one

detector of a dual short-pulse detector (initialization pulse) while

the second detector picks up target and clutter information. A

high-speed time-detector circuit measures the relative positions

of the two pulses and passes this information to a digital signal

processor. The digital signal processor then performs calculations to control detector sensitivity and to convert the time

difference to a precise measurement of distance for display as a

target.

The advantages of using the ultrawide-band width approach

are as follows:

• An ultrawide-band-based radar unit operates as a presence

sensor, i.e., it does not depend upon relative motion or Doppler

information.

• Because of the extremely short (nanosecond to subnanosecond) duration of the pulse widths and very low energy

densities, ultrawide-band systems are immune to interference from

other communication devices, electronic equipment, or motors.

• With ultrawide-band radar, range gates can be established at

user-selected distances at a precise cutoff of several centimeters

and thereby eliminate object detection beyond certain distances.

• The wide bandwidth of an ultrawide-band radar unit also

enhances the probability of detecting small targets, such as

suspended wires, poles, etc. 

The prototype radar system consists of the antenna and

electronics enclosure, a liquid crystal alarm display (LCD), and

necessary wiring (figure 33). Repackaging the antenna and

electronics enclosure will be necessary if the unit goes to
35

Figure 33.—Prototype radar system. A, Antenna and electronics enclosure; B, operator display showing range

gates.

production. The display shows an icon for the equipment along

with zones in the radar beam that represent the range gates. If an

obstacle is detected by the radar unit, the location of the obstacle

is highlighted in the appropriate range on the LCD. An audible

alarm is provided that can be shut off for each range gate, e.g., if

no alarm is desired for the farthest range, the alarm can be turned

off for that particular range.

Current Applications: 

A similar version of this radar unit is being used by the military, specifically in collision avoidance for unmanned helicopters

[Mulloy 1999].

Blind Spot Test Results:

The radar antenna enclosure was mounted near the light bar

at the rear of the truck at a height of 1.5 m (5 ft). Horizontal

polarization of the antennas gave the best results with the least

number of false alarms. Figure 34B shows the radar unit mounted

on the back of the truck with vertical polarization, which is

achieved by just turning the unit 90°.

The radar unit was tested for false alarms by driving the

dump truck in a clear field. No false alarms were heard after the

radar unit’s sensitivity was adjusted to correct levels. 

Figure 34A shows the detection zone when a person was the

target. Because of the timing of the transmitted and received

pulses, this version of the radar unit had difficulty detecting a

person nearby, as evidenced by the sporadic detection zone from

0 to 9 m (30 ft). From 9 to 13.7 m (30 to 45 ft), the radar unit

detected a person reliably.

Modifications to the radar unit are in progress. The modifications are expected to alleviate the close-range detection

problem, and the reliable detection zone will be extended to cover

both detection areas shown in figure 34A.

Figure 35 shows the results of tests when a pickup was the

target. The reliable detection zone extended from 4.6 m (15 ft) to

24.4 m (80 ft). Detection was also seen around the sides of the

truck as long as part of the pickup remained in front of the radar

unit. As with most of the other radar systems, reliable detection

and maximum range of detection depend on material composition

and cross section of the target. For this system, the sporadic

detection zone was also affected by the type of target; the zone

was significantly decreased with the pickup. 

The dump truck was driven around the test area to determine

the radar unit’s reaction to various objects. The radar unit

detected large berms (bigger than 0.5 m [1.6 ft]) while ignoring

smaller ones. It detected bushes and trees, but ignored small

foliage such as grass and weeds. The system also detected and

provided correct range information for wood power poles,

buildings, and chain-link fences as long as they were at least

6 m (20 ft) away from the truck.

SYSTEM 7 – ID INTERNATIONAL, RFID SYSTEM

Developer:

ID International Holdings (IDI), LLC, Concord, MA.

Description of System: 

This RFID-based system consists of active tags, a tag reader

mounted on the mining equipment, and an alarm display mounted

in the operator's cab and connected to the reader via cable (figure

3). Each pedestrian worker and any smaller vehicles in a work

area or job site are outfitted with tags. If a

tag is detected within range of a tag reader, an alarm is activated,

warning the equipment operator.

The first version of the tags were housed in high-impact,

sealed plastic cases approximately 6 by 7 by 2.5 cm (2.4 by 2.7

by
36

Figure 34.—Test results for Multispectral ultrawide-band radar prototype and person. A, Detection zone;

B, mounting position.
37

Figure 35.—Dectection zone for Multispectral ultrawide-band radar prototype and pickup.
38

Figure 36.–Prototype ID International tag.

1 in). A single whip-style antenna was used to transmit a lowpower, 315-MHz signal. These antennas were highly directional,

making detection dependent on orientation of the tags. Presently,

the tags are much smaller and are mounted inside a hard hat.

Two dipole antennas are used to alternately transmit the signal.

This modification improved detection, making it independent of

tag orientation. Components include a microprocessor, a 315-

MHz transmitter, and an on-board battery (figure 36).

Tag reader components include a receiver, signal conditioning electronics, and a microprocessor. The reader and a

partial-coil whip antenna are housed in a 10- by 10- by 15-cm

(4- by 4- by 6-in) NEMA-type enclosure. These sealed,

grounded steel boxes are mounted with bolts and brackets to the

host vehicle, powered by the vehicle's 12- or 24-V dc system,

and connected to the alarm unit in the operator's cab. The sealed

alarm unit has a light and 105-dB audible alarm.

For testing and development purposes, the readers have two

external switch-controlled adjustments for range and sensitivity.

There are three selectable distance ranges, (near, middle, and

far) and a continuously adjustable sensitivity setting that controls

the software's signal discernment characteristics.

Each tag transmits an "I'm here" signal three to four times

per second, alternating between the two sets of orthogonal antennas. The reader receives and processes the signal. If a valid

signal is detected within the selected range, an alarm condition

is sent to the alarm unit, which flashes the light and buzzes the

alarm. If two tags are detected in the reading range, a discernable “double buzz” alerts the driver to the presence of two or

more tags [Ruff and Hession-Kunz 1998]. Currently, the tags are

powered by lithium coin cells, which have a projected working

life of 2 years.

Current Application: 

This system has not been used in any other application.

Blind Spot Test Results: 

The tag reader was mounted on the rear of the dump truck

near the light bar. The range of the reader was adjusted to the

low setting. No false alarms were seen in a clear field.

The detection zone was interspersed with small nulls where

the tags were not detected. This was not seen as a function of tag

orientation, and it is suspected that multipath interference from

the dump truck and ground caused these nulls. An improved

antenna design and possible relocation of the reader are currently

being studied.

The range of the system extended from immediately next to

the reader out to approximately 24 m (80 ft). The width of the

detection zone extended between 12 and 15 m (40 and 50 ft) on

either side of the truck. More work is needed to obtain a betterdefined detection zone that contains no nulls and is limited to 15 m (50

ft) behind the truck and a total width of 6 to 9 m (20 to 30 ft). 

SYSTEM 8 – PITTSBURGH RESEARCH

LABORATORY HASARD SYSTEM

Developer:

 Pittsburgh Research Laboratory, NIOSH, Pittsburgh, PA.

Description of System: 

Even though this system has some significant differences, it

could be classified as an RFID-based system because it is based

on radio-frequency signal detection. The system consists of a

loop antenna that transmits a low-frequency signal and a receiver

or signal detector that receives this signal. The receiver measures and displays signal strength and can produce an alarm. The

system was originally designed to protect remote-control

operators of mobile mining equipment. The loop antenna(s) is

mounted on the machine, creating a low-frequency halo or field

around the perimeter of the machine. The receiver is worn by the

remote-control operator and warns when the operator enters this

field. The system also has the option of automatically setting the

brakes if a collision is imminent. This device was based on U.

S. Patent 5,939,986, “A Mobile Machine Hazardous Working

Zone Warning System,” which was granted on August 17, 1999

[Schiffbauer 1999].

A variation of this system was tested on the dump truck. For

this application, the transmitter and receiver locations were

reversed, i.e., the object to be avoided was outfitted with the

transmitter and the dump truck was outfitted with one or more

receivers. A 60-kHz sine wave at 40 V peak-to-peak was

transmitted through a loop antenna 135 cm wide by 124 cm long

(49 by 53 in). The antenna consisted of seven turns of 14-gauge

wire encased in PVC pipe so that a donut-shaped electromagnetic

field was generated. Different sizes of antennas or multiple

antennas can be used to vary the size and shape of the field.

The receiver for the system incorporated a simple LED bar

graph that indicated signal strength from 1 to 10, 10 indicating the

strongest signal. The receiver’s indication of signal strength was

recorded to define the detection area of the system.
39

Figure 37.–Test results for PRL's HASARD system and pickup. A, Detection zone; B, loop antenna on

truck; C, view behind truck.

Applications:

This system is currently being tested on continuous coal

mining equipment used in underground mines.

Blind Spot Test Results:

With the current configuration, a worker would have to wear

a large, high-power antenna to generate the required field, which

would not be practical. Thus, unless alternative transmitters are

developed, the current system could not be used to protect a

person. For these tests, only a pickup was used as the target.

Two configurations were tested in which the loop antenna

was mounted on top of the pickup cab (figure 37B). In the first,

the antenna was mounted directly on top of the cab against the

steel body. In the second, the antenna was mounted with a 15-cm

(6-in) offset to hold it away from the cab. The offset increased

the range of the antenna, so this configuration was used during the

final tests.
40

The receiver was mounted near the light bar at the rear of the

dump truck. Interference from the surrounding metal significantly

attenuated the signal, and a better location was found at the

outside corner of the dump truck bed (directly above the ladder

in figure 37C). While this location was used in the tests, it

would be difficult to install a final system receiver here. If this

difficulty can be overcome, a receiver could be mounted near

each corner of the dump truck to monitor all blind spots

simultaneously.

Figure 37A shows the test results for a single receiver at the

corner of the dump truck bed. The detection zone extended

from near the rear tires out to 9.1 m (30 ft) and from the sides of

the dump truck to 11.4 m (37.5 ft). This zone should extend along

the sides toward the front of the dump truck, but this area was not

tested.

This system showed promise for the dump truck; however,

more development is needed to make it suitable for surface

mining. A full description of the system as it applies to underground coal mining equipment can be found in Schiffbauer’s

report (1999).

CONCLUSIONS

RADAR SYSTEMS

Radar-based collision warning systems are the least expensive of the technologies tested. Ranging from $500 to $2,000,

radar systems are affordable to install on the front and rear of

every dump truck in a mining operation. They also require the

least amount of equipment—an enclosure for the radar unit, alarm

display, and wiring between the two. 

However, false alarms are inevitable with radar systems.

In the worst case, false alarms are short and frequent. They can

be caused by rocks or uneven terrain that would not be

considered hazardous and from abrupt truck movements and

shocks. At best, false alarms are infrequent, but still occur

because of rocks or uneven terrain. Alarms are also caused by

objects that the truck driver is aware of, such as a highwall,

berm, buildings, or another dump truck. This characteristic could

also mask the presence of an object such as a person standing

between a dump truck and a berm. False alarms are a major

concern with collision warning systems because the equipment

operator may, understandably, start ignoring alarms.

Mounting a radar unit can be time consuming, and a suitable

location can be difficult to find. Radar will detect nearby

objects, such as the rear tires of the machine, if the radar unit is

mounted near the rear axle, so care must be taken in selecting

beam widths and ranges to minimize false alarms caused by parts

of the truck itself. On some systems, finding the correct height

and mounting angle can be difficult and must be done on a trialand-error basis for each size of dump truck and for each type of

obstacle to be detected. The mounting angle of radar is

especially important when trying to detect shorter objects or

people (or a person laying down). Because of the fan-shaped

beam, low-profile objects near the radar may not be detected.

Examples of this are found in the sections describing the cinder

block tests. Mounting the radar unit on the front of the truck is

likely to be less complicated, but mounting angle and height still

must be considered. 

The detection zone of a radar unit can change depending on

the object to be detected. The mounting scheme and radar

settings for effectively detecting a pickup at a given distance

might not be the same as for detecting a person. This is

atradeoff that must be considered when adjusting the settings on

the radar unit.

None of the radar systems evaluated in this study had been

developed for, or previously tested on, large, rigid-frame dump

trucks. Thus, there are some concerns about the durability of the

enclosures and the effectiveness of the alarm displays. More

data are needed from actual tests at a surface mine before any

conclusions or recommendations can be made.

Although much was learned from testing the systems on a 50-

ton-capacity Komatsu, the results are not necessarily transferable

to larger trucks. In fact, the systems tested may have to be

modified if they are to work on larger trucks because of

differences in physical dimensions.

There is potential for significantly reducing accidents by

employing radar technology if the above concerns can be

addressed adequately. This calls for further development and

testing by collision warning system manufacturers and close

cooperation with the mining industry.

RFID SYSTEMS

Although no RFID-based collision warning systems are

commercially available for use on surface mining equipment at

this time, some of the systems tested show promise for this

application. One advantage of these systems is that they do not

generate false alarms. Either a tag is in the reading range of the

tag reader or it is not. If the system detects a tag and sets off an

alarm, the dump truck operator can be sure that there is an

obstacle in his or her blind spot. Attaching tags to objects that

are to be avoided assures that only objects of interest will

generate an alarm. Rocks, berms, or a highwall will not cause

the system to alarm.

The disadvantage to RFID systems is that a large number of

tags must be purchased and attached to pickups, graders, pedestrian workers, and any other object to be avoided. On one

hand, a simple and cheap tag would make it easy and affordable

to tag many objects. On the other, intelligent and complex tags

can provide more functionality and improved performance.

RFID-based systems tend to be more expensive than radar

systems. Tags can range from $2 to $500 each, and the cost of
41

a tag reader with an alarm display can range from $6,000 to

$20,000, depending on the quantities purchased.

The OTS systems tested were easy to mount. However,

because the detection zone can change depending on the location

of the tag reader, some care must be taken in finding a proper

mounting location. Trial-and-error in mounting is required to

optimize the detection zone for a particular dump

truck. Also, range settings must be adjusted to optimize the

detection zone for both people and vehicles because the quality

of the tag transmissions can be affected by the object to which

they are attached.

Durability will also be an issue for these systems. Tests at

an actual surface mine will be required before any of the systems

examined can go into production. 

RECOMMENDATIONS

These tests show that both RFID and radar technology show

potential in reducing accidents involving people or smaller

vehicles in the blind spots of mining equipment. More

development and testing are needed in order to meet the unique

conditions encountered in surface mining. Other specific

recommendations follow.

Because of false alarms (or real alarms from objects that

pose no danger), it is recommended that radar systems be used in

conjunction with another, secondary collision warning system,

such as video cameras. This duplication will give an operator

a warning about an object in the blind spot and a method to check

out the warning without leaving the cab. If the reliability of radar

systems increases so that false alarms are rare and multiple

objects can be distinguished, a secondary system may become

optional.

For systems using radar, the distance to a detected obstacle

should be presented in a simple way to an equipment operator.

This can be accomplished with LEDs, a graphic LCD,

distinguishable audible alarms that indicate the presence of an

obstacle in a certain range gate, or an actual distance readout.

This is especially helpful when multiple targets are in a detection

zone or cameras are not used as a back-up system. It also

provides a method of determining the closer of two objects, such

as in the case where a person is in between the equipment and the

detected highwall.

Systems based on RFID are not prone to false alarms

because of the positive nature of tag detection and therefore may

not require redundancy. However, the addition of a secondary

system, such as cameras, may be helpful by allowing the operator

to verify the location of an obstacle, especially when multiple

tags are in the detection zone. A method of indicating the

position or distance to detected tags would also be helpful.

Finally, extra precaution is needed to assure that all vehicles and

pedestrian workers at a mine are outfitted with a working tag.

When evaluating the reliability of a collision warning

system, it is important to test the system on the actual mining

equipment and while the equipment moves toward the obstacle

to be detected. This is the only way to determine if equipment

vibration and signal reflections are adversely affecting the

system. Also, it is important to verify the reliability of a system

by using the actual objects that need to be detected. Many

collision warning systems, especially radar, are sensitive to the

composition and size of the object to be detected.

No collision warning system can replace common sense and

the caution needed when operating mobile mining equipment.

However, technology can aid in reducing some of the guesswork

required when operating vehicles that have extensive blind spots.

REFERENCES

Boldt, C. M. K., and R. R. Backer. Surface Mine Truck Safety – Where Are

We? Proceedings, 28th ann. Institute on Mining Health, Safety and Research, Salt

Lake City, UT, August 25-27, 1997.

Fontana, R. J., J. F. Larrick, J. E. Cade and E. Rivers. An Ultrawide-Band

Synthetic Vision Sensor for Airborne Wire Detection. Proceedings Enhanced and

Synthetic Vision 1998, Orlando, FL, April 1998, 9 pp.

Harpster, J. L., R. W. Huey, N. D. Lerner, and G. V. Steinberg. Backup

Warning Signals: Driver Perception and Response. U.S. Department of Transportation, Technical Report, DOT HS 808 536, 1996, 62 pp.

Huey, R. W., J. L. Harpster, and N. D. Lerner. In-Vehicle Crash Avoidance

Warning Systems: Human Factors Considerations. U.S. Department of

Transportation - Summary Report, DOT HS 808 531, 1997, 35 pp.

Johnson, G. A., R. E. Griffin, and L. W. Laage. Improved Backup Alarm

Technology for Mobile Mining Equipment. Bur. of Mines Inform. Cir. 9079, 1986,

19 pp.

Mine Safety and Health Administration (MSHA). Accident Data. Accessed

July 1999 at http://www.msha.gov.

_____ Code of Federal Regulations 30, Parts 56-57, 77, 1998.

Mulloy, R. W. T. Development of an Autonomous Flight Capability for the

Hummingbird Unmanned Air Vehicle. In Proceedings AUVSI ’99, Baltimore, MD,

July 13-15, 1999.

Ruff, Todd M., and Drew Hession-Kunz. Application of Radio-Frequency

Identification Systems to Collision Avoidance in Metal/Nonmetal Mines. Presentation

at IEEE Industry Applications Society, St. Louis, MO, Oct. 12-16, 1998. (Available

on CD-ROM.)

Schiffbauer, W. H. A Workplace Safety Device for Operators of RemoteControlled Continuous Mining Machine. Am. J. of Ind. Med., Suppl. 1. Sept. 1999,

pp. 69-71.

Society for Automotive Engineers (SAE). Discriminating Back-Up Alarm

System Standard J1741. 1998, 11 pp. 

Skolnik, Merrill. Radar Handbook, 2nd ed. McGraw Hill, 1990.
42

Figure A-1.—Example of size of detection zones for sensors mounted on front bumper and rear axle of off-road

dump truck.

APPENDIX A: COLLISION WARNING SYSTEM TEST DESCRIPTION

1. INTRODUCTION

Researchers at the Spokane Research Laboratory of NIOSH

are testing various sensor systems to be used on surface mine

dump trucks to avoid collisions with objects in the truck’s blind

spots. This document outlines the procedure that will be used to

test each system. Part of the directions for the tests was taken

from SAE J1741 Discriminating Back-up Alarm System

Standard.

1

2. PURPOSE

The purpose of these tests is to determine which sensor

technologies are effective in warning a dump truck operator that

there is a person or vehicle in the blind spot of the equipment.

The results of the tests may be documented in a paper to be

published at a later date. The results of the tests are not meant to

be used for approval purposes or endorsements. 

3. DEFINITIONS

3.1 Obstacle: Object that must be avoided by the moving dump

truck. For these tests the obstacles will consist of either a person

or a pickup truck.

1

Meeting SAE, OSHA, or MSHA standards and testing for compliance are the

responsibility of the collision warning system manufacturer and end user.

3.2 Blind Spot: The areas that a truck driver cannot see while

seated in the cab

3.3 Collision Warning System: A system consisting of a sensor

and operator interface that detects nearby objects and provides

an alarm. In the case of radio-frequency-based systems, the total

system would also include the radio-frequency tags.

3.4 Sensor: The part of the system that senses nearby objects or

radio-frequency transmissions from tags.

3.5 Alarm Display: The part of the system that is located in the

cab of the truck and provides a visual and/or audible alarm

indicating that an obstacle is in the system’s detection zone.

3.6 False Alarm: An alarm indicating the presence of an

obstacle in the detection zone of the sensor when no obstacle

exists or an alarm from any object that is at a sufficient distance

to pose no danger.

3.7 Reliable Detection Zone: The area in which an obstacle is

detected 100% of the time regardless of obstacle orientation.

3.8 Sporadic Detection Zone: The area in which an obstacle

is detected some of the time but not always, i.e., less than 100%

detection, but more than approximately 10%.

3.9 Zone Depth: The distance of the detection zone measured

from the mounting location of the sensor to where detection no

longer occurs (figure A-1).
43

Figure A-2.—Fifty-ton-capacity Komatsu dump truck.

4. TEST OBSTACLES

The obstacles that must be detected by the sensor consist of

those obstacles most commonly involved in dump truck

accidents, i.e., pedestrian workers (persons) and pickup trucks.

4.1 Person 

For tests to detect a person in the detection zone of a sensor,

an SRL researcher will stand in the area of interest near the

truck. The person will be wearing a hard hat and will be

between 165 cm (65 in) and 191 cm (75 in) tall. The orientation

of the person will be varied as to which direction he or she is

facing. A mannequin, in a sitting position, is recommended by

the SAE J1741 standard. 

Because of time constraints for the testing procedure, this

was not practical. Also, some of the technologies tested are

sensitive to the composition of the test obstacle, and a mannequin

may not be an accurate representation.

4.2 Pickup Truck

For tests to detect a smaller vehicle in the detection zone of

a sensor, a three-quarter-ton, full-sized pickup truck will be

parked in the area of interest near the dump truck. Several tests

should be run with the pickup truck parked in different

orientations to determine the effect on detection range. At a

minimum, one test is required in which the pickup truck faces the

sensor system, giving the minimum cross-sectional area.

5. DUMP TRUCK DESCRIPTION

Make: Komatsu (figure A-2)

Model: 210M

Type: Rigid frame, off-highway

Capacity: 50 tons

Dimensions: Length: 9.2 m (30 ft 3 in); width: 4.4 m (14 ft 7

in); height: 4.6 m (15 ft)

Turning diameter: 21 m (69 ft) 

Tire diameter: 2 m (77 in)

Electrical system: 24 V (access to 12 V at batteries).

6. DETERMINING THE DETECTION ZONE

6.1 Test Area

During tests all personnel, except whoever is acting as the

obstacle, shall remain a significant distance away from the

potential detection zone. The test area will be an open space on

flat terrain with a sand or gravel base. No rocks, foliage, or

debris larger than 15 cm (6 in) in diameter will be in the test

area. No large objects such as buildings or berms will be within

approximately 61 m (200 ft) of the front or rear of the truck.

No large objects will be within 30 m (100 ft) from the sides of

the truck.

6.2 Test Procedure for Rear-Looking Sensors

6.2.1 False Alarms: Tests of the collision warning system

will start with no obstacles near the dump truck as defined by

section 6.1 entitled “Test Area.” With the potential detection

zones totally clear, the truck will be moved several times in

reverse to determine the frequency of false alarms.

6.2.2 Obstacle Detection: The detection zones for the rear

sensor will be determined by placing the obstacle at various

distances and locations behind the truck and recording whether

or not an alarm was activated when the truck is moved in reverse

at slow speeds (less than 8 km/h [5 mi/h]). Test points behind

the truck will be defined by a grid with a spacing of no more than

1.5 m (5 ft) between test points. Note: When testing the

detection zone for a person, it may be unsafe to move the truck in

reverse when determining detection at grid points that are very

near the truck. In this case, the person may move toward the

stationary truck to determine if detection occurs.

6.2.3 Detection Zones: The reliable detection zone will be

recorded as the area in which the obstacle is detected 100% of

the time regardless of the orientation of the obstacle. The

obstacle must be detected and an alarm indicated immediately

(<200 ms) after the truck starts moving. 

The sporadic detection zone will be recorded as the area in

which the obstacle is detected less than 100% of the time but

more than approximately 10%. Less than 10% detection will be

considered outside both detection zones, but may be noted as

false alarms.

6.3 Test Procedure for Forward-Looking Sensors 

The false alarm rate and detection zones for the forwardlooking sensor will be determined in the same way as the rear

sensor, but with the dump truck moving forward.

6.4 Sensor Mounting Locations For forward sensing, the sensor will be mounted on the front
44

 bumper or grill. For rear sensing, the sensor will be mounted

near the light bar above the rear axle (figure A-3). Other

locations may be acceptable depending on the individual

sensor’s installation instructions. If a sensor is not working to

specifications, the mounting location may be changed, but must

be in a location that does not require modifications to the dump

truck.

7. RECORDING THE DETECTION ZONES

The reliable and sporadic detection zones will be recorded

on a graph that will approximate the depth, width, and general

shape of the detection zone as seen from a top view. The zones

will be determined by placing the obstacle on a grid spacing of

no more than 1.5 m (5 ft). The height of the detection zone, as

measured from the ground, will not be recorded in these tests

except when it is necessary to investigate a sensor that is not

detecting test obstacles (figure A-1).
45

DHHS (NIOSH) Publication No. 98-

1998

To receive other information about occupational safety

and health problems, call

1-800-35-NIOSH (1-800-356-4674), or

visit the NIOSH Home Page on the World Wide Web at

http://www.cdc.gov/niosh