POWER January 2012 - 64

WORKSITE SAFETY
nizational safety practices. The technology to
collect and analyze this data was developed
as part of this project and is not currently
commercially available.
Worksite Technology Testing
The system testing occurred at a broad spectrum
of construction sites. The team selected
15 construction sites in the southeastern U.S.:
five small to large building construction sites;
seven small commercial construction sites;
two large industrial construction sites; and
one union ironworker indoor training facility.
The value of the construction work ranged
from $2 million to $1 billion, and the number
of construction workers employed ranged
from 15 to 2,000. The number of pieces of
motorized construction equipment used on
site ranged from five to 250.
Testing was performed with the proximity
warning devices on different types of construction
equipment, including wheel loaders,
forklifts, graders, forklifts, dozers, excavators,
articulated dump trucks, and mobile
cranes. Each piece of equipment was directed
to travel toward a simulated work crew. The
operator was then asked to stop the machine
once the audible or visual alert was activated
within the equipment cabin (Figure 3). The
distance between work crew and equipment
was measured, recorded, and analyzed. For
each test, the worker on foot and equipment
operator were then interviewed. Once familiarity
with the equipment was completed,
long-term testing was conducted (see table).
Five PPUs of the same configuration
were tested in the preliminary field trials.
Because each equipment type may require
its own unique signal strength, setting the
warning and alert distances at a lower level
reduces the number of nuisance alerts. The
shortest empirical warning and alert distance
from EPU to PPU was 2.8 meters (9.2 feet).
Cranes, for example, are static and alerts may
only be needed when a lift is performed. The
4. Busy construction site. Movements
of a crane, tractor and trailer, and workers on
foot on this typical worksite were followed
with real-time location tracking. Courtesy: CII
operator is able to activate the EPU/PPU alert
system only during lifts. In contrast, scrapers
can travel up to 37 miles per hour and thus
may require earlier activated alerts at longer
distances to ensure the safety of nearby
workers. All distance measurements included
the operator's reaction time and the distance
required to stop the vehicle.
The most complex tests of the proactive,
real-time proximity warning devices were
performed on two large coal power plant
projects being constructed by CII members.
One of the tests involved large earth-moving
equipment and lasted for several months.
About 20 workers were provided PPUs, and
the 30 pieces of equipment were equipped
with EPUs. By the end of the study period,
this project had performed 100,000 accidentfree
work hours.
Worker Tracking and
Data Visualization
The PPU/EPU trials also included a series
of location tracking tests. For these tests, the
helmets of construction workers were tagged
with ultra-wideband, real-time location tracking
technology on a typical worksite (Figure
4). Computers recorded the location of tagged
resources, and the information was displayed
to safety decision-makers in remote locations
(Figure 5). Finally, the location of workers,
equipment, and materials on a work site were
reported in a 3-D virtual display environment
(Figure 6).
Worker Feedback
At the beginning and end of each field trial,
participants were asked their opinions
about using the proximity and tracking deField
trials test summary. Distance measurements were made for a proactive, real-time
proximity alert device with static and dynamic construction equipment in realistic construction environments
(with obstructions present). A total of 193 equipment tests at 15 different construction
locations covering more than 100,000 accident-free work hours are included in the data. Source: CII
Average
Equipment type
Dynamic
Personnel mover
Loader/forklift
Grader and scraper
Static
Dozer
Excavator
Articulated dump truck
Mobile crane
Number of trials
4
11
10
8
8
72
80
recorded alert
distance (m)
11.9
17.8
31.5
24.5
23.4
35.6
34.0
Minimum
recorded alert
distance (m)
10.6
12.7
25.5
7.8
2.8
19.0
8.9
Maximum
recorded alert
distance (m)
13.6
29.9
50.2
43.0
38.0
50.0
62.5
5. Real-time rendering. Real-time location tracking of workers, equipment, and material are
shown in a plan view of the work site shown in Figure 4. The worker temporarily stepped out of the
way while the crane was swinging; other workers continued to work in their positions. Courtesy: CII
UWB
tag
Crane hook-671D 1Hz
Crane cabinet-6726 1Hz
Worker 0BC6-15Hz
Worker-781E 60Hz
Worker 2523-30Hz
Worker-588C 15Hz
Waiting
zone #1
A
B
C
Other workers
remain in their
position
Waiting
zone #3
Trajectory
of a worker
stepping out of
the way of the
load
64
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POWER | January 2012
Waiting
zone #2
Crane
swinging

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POWER January 2012

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