4
to achieve optimum sensing ability without interference and false alarms from other
systems was, at the very least, a tedious and time-consuming job.

The RFID tag system is currently undergoing antenna design modifications to
improve its effective range. This system needs to be designed so that it does not
sense more than the desired 40-50-ft range.

The black-and-white CCTV system successfully withstood a year’s cycle of
loading, hauling, and dumping, as well as the rigors of desert heat and cold. The
floor-mounted frame isolated the unit from cab vibrations and offered the driver a
single location for visual and verbal communication.

Another technology, the blind area viewer, which was based on the use of fresnel
lenses and an assortment of back-up mirrors, is no longer manufactured. However,

rectangular convex mirrors are standard safety equipment.


3
blind areas directly behind and to the right side of the truck. Project personnel visited
a surface mine where a black-and-white CCTV system was installed on a 190-ton
haulage truck. The rear-mounted camera successfully withstood a year’s cycle of
loading, hauling, and dumping, and desert heat and cold. The mine’s truck shop staff
fabricated a floor-mounted frame to hold a 6- by 7-3/4-in CCTV monitor as well as
a two-way radio and a truck-monitoring terminal (figure 2). The camera was
mounted on the rear axle of the frame (figure 3), and the camera monitor was wired
into the dash light system to reduce glare on the monitor during night shifts. The
screen is black until the truck’s headlight switch is on and the truck is shifted into
reverse. There is also a manual mode that leaves the monitor on continually. Since
the initial test, the mine has installed cameras on all 190 of its trucks and is testing
a second camera on the right front deck railing to capture the right-hand blind side
view. The monitor can be toggled to switch views from the right to the rear-facing

cameras.

CONCLUSIONS

After numerous shakedown tests, including locating, positioning, aiming,
adjusting, testing, tuning, and evaluating various proximity warning systems, we
concluded that Doppler radar backup alarms and RFID tag systems appear to show
promise for sensing objects within the blind arcas of vehicles. Significant efforts
must be made to achieve acceptable performance without false alarms. The Doppler
radar discriminating alarm is not a “bolt-on and plug-and-play” unit that is easy to

adapt to various situations. During the tests, it was shown that mounting the units


SURFACE HAULAGE TRUCK RESEARCH

C.M.K, Boldt, M.S., Engineering
R.R. Backer, B.S., Mining Engineer

National Institute for Occupational Safety and Health
Office for Mine Safety and Health Research
Spokanc Research Laboratory, Spokane, WA

Keywords: surface mining; truck; visibility

Reprint requests to Lani Boldt or Ron Backer
NIOSH, Spokane Research Laboratory,
314 E. Montgomery Ave., Spokane, WA 99207 USA

Tel: (509) 354-8006 FAX: (509) 354-8099 email: cth6@cdc.gov
rcb7 @cde.gov


BACKGROUND

Between 1989 and 1991, the greatest number of accidents in surface coal and
metal/nonmetal mines involved haulage trucks. In 1995, the most frequently cited
factor contributing to the 100 fatalities in these mines was powered haulage. In 1996,
over 50% of the 84 fatalities in mining that year were in surface mining. Because
some of the world’s largest mobile equipment is used in surface mincs, and this
equipment is involved in so many accidents and fatalities, new technologies are
needed to alert truck drivers and people in spaces around the truck to the possibilities

of collisions.

METHODS

NIOSH studies have focused on off-the-shelf technologies that would enable
mine haulage truck drivers to “see” objects and people behind and to the side of a
moving vehicle. This paper discusses two types of systems currently available:
proximity warning devices and charge-coupled device (CCD) cameras having closed-

circuit television (CCTV) monitors.

RESULTS

Off-the-shelf Doppler radar alarm units were evaluated as to their effectiveness
when mounted on large trucks. Laboratory and field tests were conducted to
simulate mounting and operating the units on large haulage vehicles. Field tests were
then conducted using 240-ton mining trucks at a truck manufacturing facility.

Various mounting and aiming schemes were tried to examine how sensitive the units


2
were to detecting a pickup truck and/or people behind the truck. Since the detectors
can only sce 5 ft left and right of the centerline of focus, two units were needed to
cover the 20-ft width of the haulage trucks. In the first configuration, two backup
alarms were attached with magnetic base plates to the rear light alarm bracket (figure
1) ata height of 8 ft above the ground. The units were focused from 20° to 25° off
horizontal and were aimed so that the beams crossed or diverged. When the backup
tests commenced, there were false alarms resulting from changes in the road surface,
rotation of the rear wheels, and surrounding buildings and other structures.

Because earlier laboratory tests demonstrated better results with higher gains
when the sensors were II to 12 ft above the ground, the sensors used in the field test
were moved higher on the truck, to 14 ft above the ground on the hinge point for the
dump body. The radar units were focused over the tire toward the “footprint”
directly in back of each unit and downward 30° from horizontal. They were then
adjusted to about 50 pet gain. In this position, the units were able to sensc the pickup
truck at distances of 21 to 24 ft behind the haulage truck. No false alarms went off
in this configuration.

A second proximity warning system currently being investigated is a radio
frequency identification (RFID) tag system. This system transmits radio signals that
are picked up by a receiver (tag) on a person or object. Current designs for this
system require that a continuous alarm sounds when the units are within 40 ft of the
tag. All utility vehicles, personnel, or other objects requiring sensing would need to
be tagged. Results are forthcoming.

Another system being evaluated is a video camera and monitor that display the