EXPERIMENTAL STUDY ON FUNDAMENTAL PERFORMANCEOF SAFETY BELTS FOR FALL PREVENTION
Yasumichi HINO1, Hiroki TAKAHASHI1 and Katsutoshi OHDO1
1National Institute of Occupational Safety and Health, 1-4-6 Umezono, Kiyose,Tokyo 204-0024, Japan

Many fatal accidents due to falling from heights have taken place at construction
sites in Japan. The purpose of this study was to determine the fall prevention
performances of different types of safety belts. Simply drop tests were carried outto measure the impact load and the posture of a human dummy using a Hybrid-Ϫpedestrian model and a sandbag. The probability of human injury and themagnitude of the impact force were examined by comparing the experimentalresults. The results point to the value of the harness-type safety belt. They also
highlight the need to add a shock absorber device to absorb potential energy andprevent serious injuries.

Introduction
In Japan, most fall prevention countermeasures aim to ensure the stability and upright posture ofworkers while working different types of work surfaces. These countermeasures are establishedin Japan in clause 1 of article 518 and 519 of the occupational safety and health regulation.
Figure 1 shows an example of the principal countermeasures applied during repair work on aresidential house.
Irrespective of these measures, many labor accidents due to falling has continued to take

Collapse556䠄3%䠅

Collapse
Crash 15䠄4%䠅
19䠄5%䠅

Others2,224
䠄13%䠅

Fall to thesame level
20䠄5%䠅

Clash
754䠄4%䠅

Fall from height
5,802
䠄34%䠅

Fall on the same level1,592䠄9%䠅

Crashed841䠄5%䠅

Crashed21䠄5%䠅
Sharp/Rub26(7%䠅Sharp/Rub
1,640
Sandwiched
䠄10%䠅
1,811䠄11%䠅

Others22
䠄6%䠅

Fall from height
182
䠄47%䠅

Sandwiched
39
䠄10%䠅
Flying/Falling Objects
1,763䠄10%䠅

Flying/Falling Objects
41䠄11%䠅

Total number of labor accidents Labor accidents in the disasterthe construction
siteof East
Earthquake
Photo
1. Fundamental safetyinmeasure  industry
Photo
2. Oneof thedisaster
sites
due
Figure1.
measures
Figure2.
A disastersitesJapan
East
Japan
in the housing
works works to east Japan earthquake
following
the housing
Earthquake- 189 -Collapse
556䠄3%䠅

Collapse
Crash 15䠄4%䠅
19䠄5%䠅

Others2,224䠄13%䠅

Fall to thesame level
20䠄5%䠅Clash754䠄4%䠅

Fall from height
5,802
䠄34%䠅

Fall on the same level1,592䠄9%䠅

Crashed841䠄5%䠅

Crashed21䠄5%䠅
Sharp/Rub26(7%䠅Sharp/Rub
1,640
Sandwiched
䠄10%䠅
1,811
䠄11%䠅

Others22
䠄6%䠅

Fall from height
182
䠄47%䠅

Sandwiched
39
䠄10%䠅
Flying/Falling Objects
1,763䠄10%䠅

Total number of labor accidents in theconstruction industry in Japan

Flying/Falling Objects
41䠄11%䠅

Labor accidents in the disaster site of East
Japan Earthquake and Tsunami

Figure 3. Labor accidents in the construction industry in 2011
place in the construction industry, as shown in Figure 3 (Ministry of Labor Safety and HealthJapan, 2012). In the disaster relief works following the East Japan Earthquake and the major
tsunami happened in march 2011, there was a high rate of falling accidents. Figure 2 shows oneof the repair or dismantle work sites in the Tohoku region damaged by the natural disaster. It isquite difficult to carry out the required countermeasures in such a construction site. Establishing
fall prevention measures for such sites is one of the most urgent tasks (National Institute ofOccupational safety and Health, 2011).
Clause 2 of article 518 and 519 of the occupational safety and health regulation refers to useof safety belts as a countermeasure. However, concrete methods are not established. A previous
statistics analysis of fatal labor accidents at disaster construction sites revealed the following:(Yasumichi, 2011)(1) Fall related accidents accounted for about one-third of all accidents.
(2) Nearly 90% of fatal accidents in building or housing construction were due to falls.
(3) A total of 75% of falls at sites were due to falls from roofs.
“The harness-type safety belt” is widely used throughout the world, but it is rarely
employed in Japan (National Institute of Industrial safety, 1999). Instead, the waist-belt-typesafety belt is used almost 100% of the time. The purpose of this study was to determine the fall
prevention performance of these two types of safety belts..
Experimental Methods
This study focused on fall prevention measures used in roof repair works, as shown in Figure 4.
Simply drop tests were carried using the two different types of safety belts, and the results werecompared.

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Table 1. Fatal labor accidents in disaster relief work (1985 to 2005㸧
Fatal labor related
accidents
TotalFalls (from roof)
Construction machinery
Landslides
Collapse
Flying/falling Objects
Traffic
Crane
Drowning
Electrification
Other

Number
356
106
9149
18162714
12617

Building or housingworks
NumberRate
61
100%
53 (46)87% (75%)
12%
00%
12%
12%
23%
00%
00%
23%
12%

Civil engineering
works
Number
Rate
292
100%
50
17%
9031%
49
17%
176%
155%259%
145%
124%
41%
165%

Figure 4. An example of a repair sites
Figure 5 shows the experimental parameters and conditions used in each test. The hook ofthe safety belts was fixed to the assumed main rope located on the surface of the roof at heightof about 1m lower from the gravity. Two types of falling bodies, a sandbag or a Hybrid-Ϫpedestrian human dummy, were dropped from the assumed eave of the roof using separating
devices. The weight of each falling body was 75kg. The ropes of the safety belts used in thisexperiment were all made with nylon and new. They were 1700mm long and did not have any
additional functions, such as shock absorber device. The impact loads acting on the rope were
measured with load cell. A high speed camera was also used in the experiments to realize basic
characteristics of human dummy posture while falling.
- 191 -

Load cell

Rigid body

Height of theCenter of gravity

Height of theCenter of gravity

Height of theCenter of gravity

1m

Separating device

Separating device

Separating device

1m

Load cell

Load cell1mRigid body

Rigid bodyFree fall

Free fall

sandbag䠄75kg䠅

HybridϪ䠄75kg䠅

HybridϪ䠄75kg䠅

Waist belttype
typesafety
safety belt
belt
NormalWaist belttype
typesafety
safety belt
belt
NormalHarness type
Harnesstype safety
safetybelt
beltFree fall

Figure 5. Experimental parameters and conditions
Experimental Results
Photo.1 shows the posture of the Hybrid-Ϫ pedestrian human dummy while falling. In theexperiment using a waist-belt- type safety belt, the neck or waist parts of the HybridϪ
pedestrian model was bent considerably during the falling. From the results of the posture
shown in Photo.1, spinal cord injury at the neck or waist may occur if worker used a waist-belttype in the same falling situation. In contrast, very little bending of the human dummy occurredin the experiment with the harness-type safety belt. Instead, the head part of the human dummy
remained upright, and the leg part remained down side.
Figure 6 shows the time histories of the impact force acting on the safety rope of each typeof safety belts. The impact force on the harness-type was similar to the impact force on thesandbag. The duration was also similar. In contrast, the impact force on the waist-belt-typesafety belt was smallest in all the experiments. Thus, the duration is longer than other type
experiments.
From these results, the harness-type safety belt cannot be expected to reduce the impact
force and energy during falls. However, the risk of serious head injury could be expected to berelatively low, because the falling posture was quite stable when the human dummy wore theharness-type. In addition, excessive bending of the waist would be low. With the waist-belt-typesafety belt, the risks of serious head injury and body part injuries due to excessive bending
would be very high, because the falling posture might be a handstand posture and he worker’s
head may crash directly into some construction equipment or the rigid grand surface.
Figure 7 shows labor accident statistics data on the main parts injured in victims of fatal falls
during 30 years in Japan. This figure shows that head injuries account for most of the damage
during falls. Therefore, it is important to reduce the risk of head injury for prevention of fatal
accidents and physical impediments.
- 192 -(a) Using a waist-belt-type safety belt(b) Using a harness-type belt

Photo 1. Postures of the human dummy during the drop tests


Summary
The results raise concerns that serious head injury and body part injury may occur due toexcessive bending during falls when the waist-belt-type safety belt is worn. In contrast, the riskof serious head injury appears to be relatively low with the harness-type belt because the falling
posture was quite stable in the tests with human dummy. However, the harness-type safety belt
cannot be expected to reduce the impact force and energy during falls. Therefore, the harnesstype safety belt with an added shock absorber device to absorb potential energy is strongly
recommended for prevention of serious injuries and physical impediment.

- 193 -Harness type
type safety
safety belt
beltHarness(HybridϪ:solid䠄HybridϪ䠖Solidline)
line䠅

8㻌

Waist belt
type
safetyNormaltype
safetybeltbelt(sandbag:dotted䠄sandbag䠖dottedline)line䠅

6㻌

Impact Force (kN)

104Normal
typetype
safetybeltbelt
Waist belt
safety䠄HybridϪ䠖dashline䠅(HybridϪ:dash line)

200

100

200

300400500

Time (msec)

Number of Fatal falling accident

Figure 6. Impact force on the lanyard due to fallUnknown
OthersNeck part
Head partyear

Figure 7. Number of fatal falls divided into main injury region
References
Ministry of Labor Safety and Health Japan. (2012). Labor accidents reports on casualties
disease. (in Japanese)
National Institute of Occupational safety and Health & Japan Safety Appliance
Association. (2012). Fall prevention method and the relative equipments on the roofand house repair works. Committee for the fall prevention from roof and house. (inJapanese)
National Institute of Industrial safety. (1999). Recommendation for Construction of Safety
Belts. Technical recommendations of the National Institute of Industrial Safety. (inJapanese)
Yasumichi HINO. (2012). New prevention methods for falling accidents due to disaster
repair works at building construction site. 10th International conference on
Occupational Risk Prevention, ORP2012, (CD-ROM).

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