Measurement and Evaluation of Visibility 

Experiments for Powered Industrial Vehicles

Roger Bostelman

U.S DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Intelligent Systems Division 

Gaithersburg, MD 20899-8230 

Li Peng Liang

University of Maryland, College Park 

College Park, MD 20742 

NISTIR 7837
 

NISTIR 7837

Measurement and Evaluation of Visibility 

Experiments for Powered Industrial Vehicles

Roger Bostelman

U.S DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Intelligent Systems Division 

Gaithersburg, MD 20899-8230 

Li Peng Liang

University of Maryland, College Park 

College Park, MD 20742 

December 2011

U.S. DEPARTMENT OF COMMERCE 

John Bryson, Secretary 

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY 

Patrick D. Gallagher, Under Secretary for Standards and Technology and Director 
 1 
2

Abstract

Powered industrial vehicles, such as forklifts, are widely used in manufacturing and other 

industries. Potential safety issues exist due to limitations in the operator‟s ability to see all 

around the vehicle. Areas the operator cannot see are called non-visible vehicle regions. Nonvisible regions for operators of powered industrial vehicles are mainly caused by vehicle 

obstructions The regions are required to meet certain criteria specified by standards. American 

National Standard Institute (ANSI)/Industrial Truck Standards Development Foundation 

(ITSDF) ANSI/ITSDF B56.5, ANSI/ITSDF B56.11.6, and International Organization for 

Standardization/Draft International Standard (ISO/DIS) 13564-1 standards require measurement 

and evaluation of visibility from powered industrial vehicles. The National Institute of Standards 

and Technology‟s (NIST) Intelligent System Division has been researching advanced 2D and 3D 

imaging sensors for improving both automated and manned forklift safety. Improvements are 

expected to provide 3D obstacle detection for both vehicle types. It is important to understand 

non-visible region locations initially, since that would then determine what type of 3D imagers 

would be required and where the sensors would be mounted. Visibility of a forklift was 

evaluated at NIST by following the above ANSI and ISO standards through 11 tests which set 

criteria based on the patterns of shadows cast when the forklift does not carry any load. Also, 

new test methods were created and tested. The new test methods were based on the forklift 

carrying loads and using standard sized test pieces and a mannequin. The NIST experiments, 

tests methods, and results are detailed in this report. This report will then serve as a basis for 

further advanced visibility and semi-automated powered industrial vehicle safety performance 

measurements and test methods development.

Keywords: ANSI/ITSDF B56 standards, visibility, powered industrial vehicles, forklift, 

safety, recommendations
3

Table of Contents

INTRODUCTION.........................................................................................................................................................4

BACKGROUND...........................................................................................................................................................6

EXPERIMENTAL SETUP ...........................................................................................................................................7

EXPERIMENTS..........................................................................................................................................................14

EXPERIMENTAL RESULTS ....................................................................................................................................16

RESULTS OF ADDITIONAL EXPERIMENTS........................................................................................................19

RECOMMENDED IMPROVEMENTS TO CURRENT STANDARDS ...................................................................23

ISO/DIS 13564-1 and ANSI/ITSDF B56.11.6 ..................................................................................................23

ISO 5353: 1995 .............................................................................................................................................29

SUMMARY AND CONCLUSIONS ..........................................................................................................................30

ACKNOWLEDGEMENTS.........................................................................................................................................31

REFERENCES ............................................................................................................................................................31

APPENDICES.............................................................................................................................................................33

Appendix 1 - Modified SIP Apparatus Design..................................................................................................33

Appendix 2 - Forklift Test Orientation and Patterns of Shadows ........................................................................34

Appendix 3 - Recent and planned visibility efforts............................................................................................36

 

List of Tables

Table 1. Forklift specifications ............................................................................ 7

Table 2. Description of visibility tests ................................................................... 14

Table 3. Test results of travelling mode of forklift .................................................... 18

Table 4. Test results for maneuvering mode of forklift ................................................ 18

Table 5. Test results with forklift carrying a pallet of boxes ......................................... 20

Table 6. Results when fork arms were raised to 117mm above floor ................................ 21
4

INTRODUCTION

Powered industrial vehicles are widely used in many industries. There are over 1 million forklifts 

and nearly 2000 automated guided vehicles (AGVs) in use in the United States. The number of 

forklift operators is estimated to be 2 million (6 million including part time operators) [1]. 

Forklifts are necessary vehicles for materials handling and delivering. However, forklifts can be 

a hazard to drivers and pedestrians if not operated properly or if non-visible regions due to 

forklift structure and loads they carry are not addressed. Training and forklift activity 

monitoring are being addressed through driver education, tracking technology, and supervision. 

According to American National Standard Institute (ANSI)/Industrial Truck Standards 

Development Foundation (ITSDF) [2] B56.1, the manned industrial lift truck operator is 

responsible for vehicle control. Safe speeds, driver training, and other vehicle operator 

responsibilities must also be adhered to according to the standard. Visibility from within 

forklifts or other powered industrial vehicles is typically measured by the vehicle manufacturer 

according to visibility standards, such as International Organization for Standardization/Draft 

International Standard (ISO/DIS) [3] ISO/DIS 13564-1 [4] and ANSI/ITSDF B56.11.6 [5] 

which allow up to 20 % non-visible regions. Non-visibility is being addressed through 

commercial, off-the-shelf forklift tracking, cameras, barriers, etc. [6] However, even with these 

operational and visibility solutions and standards, forklift accidents frequently occur. Accidents 

statistics involving forklifts were presented at the 2010 “Towards Improved Forklift Safety” 

workshop and summarized in [6]. For example: 

OSHA estimates that there are 110 000 accidents each year. 

Almost 80% of forklift accidents involve a pedestrian.

According to OSHA, approximately 70 % of all accidents reported could have been 

avoided with proper safety procedures. 

In the next generation manufacturing facility, the Intelligent Systems Division (ISD) at the 

National Institute of Standards and Technology (NIST) envisions increased human-vehicle 

collaboration [7] Current forklift visibility standard criteria are likely insufficient in providing 

guidance for this kind of operation with respect to safety. Therefore, NIST ISD has been 

researching advanced 2D and 3D imaging sensors for viewing the local environment of AGVs

and recently, to address the issue of forklift safety. Several safety technology implementation 

concepts for manufacturing vehicles were presented in [6] including use of 3D imagers mounted 

on a forklift and used as non-visible region detection devices to assist drivers. It may be feasible 

to integrate the 3D sensor information with driver alerts (e.g., audible, visual, etc.) and/or to 

provide semi-autonomous slow/stop functionality to prevent accidents when the driver doesn‟t 

see the hazard.

The test methods in current visibility standards do not determine exactly where non-visible 

regions occur, only that they do or do not occur. These non-visible regions must be known for 

sensor manufacturers and integrators to determine what 2D and 3D imaging devices are useful 
5

for this safety application and where they are best mounted on industrial vehicles to provide the 

most cost effective solution. It is also unclear in the current visibility standards, how well the 

test method results determine the non-visible regions. Many lamps are used simultaneously for 

most standard tests to illuminate an area resulting in few shadows created by vehicle obstructions 

and therefore, visibility appears to meet visibility standard requirements. However, it is obvious 

to a viewer sitting in the vehicle driver‟s seat that vehicle obstructions exist. 

In order to fully understand how visibility standard test methods determine non-visible regions

and if necessary, how these methods can or should be improved, ISD researchers first

implemented the visibility standards on a forklift. The results provided the basis for

recommendations for improving current visibility standards. One key result is that the standard 

test method of turning on all the lights at the same time did not effectively simulate the positions 

of two eyes of an operator. A forklift (Figure 1) owned by the NIST ISD was used for visibility 

testing according to the ANSI/ITSDF B56.5 [8] and ANSI B56.11.6 [9] standards and the

ISO/DIS 13564-1 and ISO 5353 [10] standards. Specifications of the forklift are presented in the

Background section. The NIST ISD tests were not meant to evaluate whether the forklift used

can pass the standard visibility tests. Instead, the forklift was used to evaluate visibility 

standards and determine the potential need, type, and location for 3D imagers.

The specific standards referenced for the visibility tests and forklift safety operation were:

ANSI/ITSDF B56.11.6: 20xx - Evaluation of Visibility From Powered Industrial Trucks

ANSI/ITSDF B56.5: 2010 - Safety Standard for Driverless, Automatic Guided Industrial 

Vehicles and Automated Functions of Manned Industrial Vehicles

ISO/DIS 13564-1: 2007 - Powered Industrial trucks – Visibility - Test methods and 

verification-Part 1: Sit-on and stand-on operator trucks and variable reach trucks

ISO 5353: 1995 - Earth-moving machinery, and tractors and machinery for agriculture 

and forestry-Seat Index Point

This paper describes the apparatuses needed for the visibility tests. The procedures of the 

visibility tests and experimental setup are also discussed. By following standard ISO 13564-1, 

eleven (11) visibility tests were conducted. Test results are discussed followed by recommended 

improvements to the standards and conclusions. Appendices provide additional information on 

apparatus design, shadows produced from tests, and other recent advanced visibility efforts.
6

Figure 1. Forklift1used for Visibility experiments.

BACKGROUND

Draft International Standard ISO/DIS 13564-1 is based on the current ANSI B56.11.6 standard 

for visibility tests of powered industrial vehicles. ISO/DIS 13564-1 is now being rewritten. 

Upon completion of the ISO standard, the ANSI 56.11.6 standard will again be addressed and 

updated according to the latest ISO 13564-1 standard. 

Both ISO and ANSI standards state that the visibility of the operator sitting inside the forklift is 

required to meet certain criteria - generally to have 20 % visibility of specific sized targets placed 

at specified locations. ISO/DIS 13564-1 and ISO 5353 were followed and applied to the ISD 

forklift. A light source array is used to determine obstructed lines-of-sight from a position 

comparable to that of an operator‟s eyes. ISO/DIS 13564-1 specifies the exact locations of the 

light source array to simulate the positions of the operator‟s eyes. This point is critical since (a) 

the operator can move his/her head for better visibility and (b) the operator also has peripheral 

vision. For (a), the standard tests mandate the use of a 13 lamp array which simulates operator 

head movement. For (a) and (b), the standard tests mandate rotating the lamp array about a 

known point.

The location of the lamp array is based on a reference point called the Seat Index Point (SIP)

located on an SIP apparatus. The SIP apparatus is specified in and was fabricated at ISD 

following ISO 5353. Once fabricated, the SIP apparatus was placed on the operator seat

according to ISO/DIS 13564-1and the position was adjusted using the specified 400 N vertical 

and 100 N horizontal forces which simulate an average weight operator sitting on the seat. 

 

1

 Commercial equipment and materials are identified in this paper in order to adequately specify certain 

procedures. Such identification does not imply recommendation or endorsement by the National Institute of 

Standards and Technology, nor does it imply that the materials or equipment are necessarily the best available for 

the purpose.
7

Muslin cloth, as specified by 13564-1, was not used since both the seat and SIP apparatus were 

considered smooth surfaces with very low friction between them. The lamp array could then be 

mounted to the forklift with position referenced to the SIP. Once mounted, the array can then be 

rotated to specified angles to simulate the rotation of the operator‟s head. The shadows from the 

lamp array from within the forklift were displayed on a screen positioned and moved along test 

paths around the forklift. The shadow areas were summed and required to meet the standard

specifying at least 80 % of the test screen be illuminated by a varied set of lamps. For example, 

eleven tests included illuminating four outside lights (two on either end), nine center lights, all 

thirteen lights or any two lamps separated by 75 mm. The test results are discussed in the 

Discussion of Results section. All eleven visibility tests simulate two major forklift operation 

modes: Travelling and Maneuvering. Three tests simulated the travelling mode and the 

remaining tests simulated maneuvering mode. 

Forklift specifications are shown in Table 1 as directed in ISO/DIS 13564-1 Section 10.1 Truck 

Information. This table shows the test report‟s Truck information required for visibility reports.

Table 1. Forklift Specifications

a manufacturer V.MARIOTTI

b model MYCROS 8C

c serial number 62,5/3339

d capacity and load centre 794 kg (1746 Lbs)

e

description of lifting 

mechanism

lift height

number of stages 2

lowered height floor

reach 320 cm (126 in)

f tire information PM 267*127*65.1

g

location and dimensions of 

truck profile in 3.2 N/A

h

location of SIP and seat 

information, direction of the 

seat (see fig 9) direction: Forward

i stand-on truck info. N/A

j

location an description of 

auxiliary equipment for 

indirect visibility N/A

EXPERIMENTAL SETUP

Apparatuses were designed and fabricated to use in the experiment according to visibility 

standards. These apparatuses included the: 1) 13 lamp array; 2) test body and test screen; 3) Seat 

Index Point (SIP) apparatus; 4) 100 N horizontal and 400 N vertical force application 

apparatuses that applied and forces to the SIP apparatus; and 5) lamp array electronics and a 
8

power supply. The test paths for eleven visibility tests, as specified in ISO/DIS 13564-1, were 

also marked on the floor. Each apparatus is explained in more detail and shown in Figures 2 

through 6 with the entire experimental setup shown in Figure 7. Apparatuses designed and used 

are detailed here so that they can be mimicked by manufacturers, potentially saving time and 

effort. The Recommendations section includes possible improvements in apparatus design and 

development methods.

1. Light Source Array

Thirteen 55 W halogen lamps were used to generate light from within the forklift and were 

mounted at the specified location according to ISO/DIS 13564-1. Lamps were separated by 37.5 

mm and numbered according to ISO/DIS 13564-1 as in Figure 2 (b) front/end view and position 

numbered as in Figure 2 (b) top view. Thirteen incandescent lamps were also initially tested and 

determined to provide unclear edges and therefore, not used for standard tests. Both sets of 

lights are shown in Figure 2 (a). A combination of incandescent and halogen was also tested with 

little improvement. Therefore, the standard was followed using only the top row of halogen 

lamps positioned as instructed in the standard. The lamp layout and numbering is shown in 

Figure 2 (b).

a

13 halogen lamps

13 incandescent 

lamps
9

b

Figure 2. (a) Light source arrays, including: halogen (top row) and incandescent (bottom 

row); (b) Halogen lamp layout design.

2. Test Body and Test Screen

The 500 mm x 1200 mm test body and 500 mm x 1500 mm test screen (includes the test body), 

as shown in Figure 3, were drawn on a white board. The test body and test screen were drawn as 

specified in ISO/DIS 13564-1. 

Figure 3. Test body and test screen

Test body

Test screen
10

3. Seat Index Point Apparatus 

ISO 5353 details the SIP apparatus as shown in Figure 4 (a). Since the back of the SIP apparatus 

was relatively complex to design and build, a modified design was used as shown in Figure 4 (b). 

Computer aided designs of the differences of specified standard and the as-built SIP apparatus 

used for ISD tests are shown in Appendix 1 – Modified SIP Apparatus Design. Similar contact 

points are applied to the seat as in the ISO 5353 specified design since wooden blocks combined 

with curved aluminum were used in the ISD design to fill the specified outside contact surface.

a

b

Figure 4. Seat Index Point Apparatus (a) as specified in ISO 5353 showing top (left drawing) and 

side (right drawing) views and (b) as-built by NIST ISD.

Seat Index Point 

Apparatus
11

4. Horizontal and Vertical Force Application Apparatuses

The 100 N horizontal force was applied by a researcher (see Figure 5 (a)) through a piece of 

extruded aluminum bar and measured using a spring scale. A second researcher measured the 

distance between the point of applied force and an aluminum crossbar temporarily attached to the 

forklift. Following the measurement, a push bar was cut and inserted between the force 

application point and the cross bar (see Figure 5 (b)). 

A 400 N vertical force was applied by adding weights to the SIP apparatus (see Figure 5 (b)). 

The weights were suspended on both ends of an aluminum bar using threaded rods. The bar also 

included a 10-32 bolt protruding from its center and was used to apply a point load to the SIP at 

the standard specified location.

a

b

Figure 5. Applying (a) horizontal and (b) vertical forces. The spring scale shown in (a) indicates 

the applied force on the SIP device.

push bar
12

5. Electrical Circuits and Power Supply

A lamp switch box was designed and built and powered by a 55 Amp power supply as shown in 

Figure 6 (a). The lamp switch configuration was designed as in ISO/DIS 13564-1 to turn on 

only the specified lamps. Four circuit breakers were used as switches to power various 

combinations of lights as shown in the schematic in Figure 6 (b). 

a

b

Figure 6. (a) Electrical setup: (left) power supply and (right) lamps switch box; (b) Lamps wiring

diagram.
13

The entire experimental setup is shown in Figure 7. Note that the forklift locator line shown in 

Figure 7 (bottom) is not a test path. It was simply used as a marker in case the forklift was 

moved.

Figure 7 – Experimental setup showing all components.

Adjustable U-frame support 

for lamp array

Forklift frame

Rotary joint

Lamp array

Test Screen

SIP apparatus

Push rod applying horizontal 

force

Mannequin 

Lamps (facing forward)

U-frame support

Electronics

Pallet

Forklift

Weights for vertical 

force on SIP apparatus 

Forklift locater line
14

EXPERIMENTS

Eleven tests were performed to evaluate the visibility from within the forklift when the lamp

array was rotated to different directions. For each test, the test body or test screen was moved 

along the test paths specified by the standard. Percentage of shadows and illuminated areas 

associated with the specific location along the test path were then recorded. The visibility tests 

were conducted by following ISO 13564-1. Table 2 shows a description of the 11 visibility tests

and Figure 8, included from the ISO/DIS 13564-1 standard, shows the test paths used. Test 

direction values are shown in Figure 18 (a) in Appendix 2 - Forklift Test Orientation and Patterns 

of Shadows. Forward is equivalent to 0°. Distance of lights to axis of rotation is shown in Figure 

18 (b). 

Table 2. Description of visibility tests

Test No. Tests Test 

Direction

Distance of 

lights to axis 

of 

rotation(cm)

Number of 

Lights

Test path Test Object

1 Travelling Forward 125 9 P1.1-P1.2 Test body 

2 Travelling - 125 9 P2.1-P2.2 Test body

3 Travelling Forward 125 2 P1.1-P1.2 Test screen

4 Maneuvering Forward 125 13 P3.1-P3.2 Test body

5 Maneuvering 125 13 P4.1-P4.2 Test body

6 Maneuvering 125 13 P5.1-P5.2 Test body

7 Maneuvering 125 13 P6.1-P6.2 Test body

8 Maneuvering 125 13 P7.1-P7.2 Test body

9 Maneuvering 125 13 P8.1-P8.2 Test body

10 Maneuvering 125 13 P9.1-P9.2 Test body

11 Fork arms Direction of 

load center

275 13 N/A Load 

carrying 

device
15

Figure 8. Tests Path (excerpt from ISO/DIS 13564-1 FIG 7, P. 16).
16

NIST researchers performed additional experiments beyond the tests specified in ISO/DIS 

13564-1, including:

1. Use of incandescent lamps instead of halogen lamps

Reason: ISO/DIS 13564-1 states the use of 13 x 55W (12 V) lamps totaling 715W when 

all lamps are on. Because the lamps are 12 V powered, a power supply of nearly 60 A is 

required to meet this criteria. Incandescent lamps are 120 V (in the US) x 60 W 

(standard) each. They can use typical alternating current power at 0.5 A each or 7.5 A for 

all 13 lamps with no additional power supply required. 

2. Use of 13 incandescent and 2 halogen lamps

Reason: As in 1 above, power is the main issue. However, incandescent lamps do not 

produce clear shadow edges from vehicle obstructions as do halogen bulbs. The 

combination was therefore tested.

3. Use of loads carried by the forklift

Reason: the forklift is frequently loaded. Forklift operators must be able to use the 

forklift during these times, too, and have appropriate visibility to control the vehicle 

safely. Therefore, tests were completed using underslung and palletized loads. 

Added to this test was the use of more human-type test bodies instead of a screen. 

Reason: Since one main concern with operator visibility is to see pedestrians when 

carrying loads, standard test pieces specified in ANSI B56.5 and a mannequin were used. 

ANSI B56.5 test pieces simulate a person‟s lower leg when standing (70 mm diameter x 

400 mm high) and a person‟s torso when they have fallen down (200 mm diameter x 600 

mm long). The mannequin was 1.8 m high. For these tests, NIST researchers set 

questions to be addressed as: Can the test pieces be seen? For the mannequin, which 

body part(s) can or cannot be seen?

The results of the additional experiments are summarized in the Results of Additional 

Experiments section.

EXPERIMENTAL RESULTS

Most of the tests results for the forklift used met the criteria specified by the ISO/DIS 13564-1

standard which requires that the percentage of area illuminated by at least one light be at least 

20 %. For those results that met the criteria, the percentage of illuminated area was very high, 

around 100 % as shown in Table 3. This was because 9 or all 13 lamps, depending on the test,

were turned on simultaneously to simulate the range of positions of an operator‟s eyes from head 

movement. However, this simulation was not very accurate because although the two eyes of an 
17

operator could actually reach any position within the width of the lamp array, the operator‟s eyes 

cannot reach all the positions at the same time. 

For example, in test 1, nine lamps were turned on according to the standard. Illuminated areas

were 100 % as shown in Figure 9 (a). However, with just two lamps (No. 9 and No. 11) turned 

on, the percentage of illuminated area dropped to 0 % as shown in Figure 9 (b). Therefore, there 

was a blind spot with the two eyes at locations of lamps 9 and 11. Since the percentage of 

illuminated area was almost 100 % for all the standard tests and the test results did not show the 

existence of blind spots, the simulation was not accurate, although the results meet the criteria of 

the existing standard.

a b

Figure 9. (a) Shadows of test1, (b) Shadow of test 1 with just two lamps separated by 75 mm

turned on

Test results directed by ISO 13564-1 include these points:

1) There were no auxiliary equipment used in the tests

2) For test 3, the lamps used were No. 3 and No. 5

3) For test 11, distance between lamps axis and axis of lamps rotation was 275 mm.

4) Height of load carrying surface for test 11 was 200 mm; height of load carrying surface 

was 0 for all other tests. 

5) Number of lamps that were not used in 5.13 was none. 

Tables 3 and 4 include test results for traveling mode and maneuvering mode, respectively, and 

include the following rows:

a: test number

b: percentage of illuminated area for all dark shadows
18

c: position of test body on the test path or location of dark shadow on the screen – test positions 

are with respect to Figure 8 - Tests Paths as excerpt from ISO/DIS 13564-1 FIG 7, P. 16.

The percentage shown in each column under each test is with respect to row c test body and test 

path position. For example, under Test 1, the percentage is 100 % illumination with the left edge 

of the test screen at position P1.1.

Table 3. Test results for traveling mode of forklift

a) test 

number

b) percentage of 

illuminated area 

for all dark 

shadows

c) position of test body on the test 

path or location of dark shadow 

on the screen

Test 1 100 % left edge of screen at P1.1

100 %

center of screen at longitudinal axis 

of forklift

100 % right edge of screen at P 1.2

Test 2 100 % right edge of screen at P2.1

100 %

center of screen at midpoint of 

P2.1 and P2.2

100 % left edge of screen at P2.2

Test 3 100 % left edge of screen at P1.1

100 %

center of screen at longitudinal axis 

of forklift

100 % right edge of screen at P 1.2

100 % right edge of screen at P3.1

100 %

left edge of screen at 60 mm to 

the right of P3.1

95 % left edge of screen at P2.2

Table 4. Test results for maneuvering mode of forklift

a) test 

number

b) percentage of 

illuminated area 

for all dark 

shadows

c) position of test body on the test 

path or location of dark shadow 

on the screen

Test 4 100 % right edge of screen at P3.1

100 %

left edge of screen at 60 mm to 

the right of P3.1

95 % left edge of screen at P2.2

90 %

left edge of screen at 120 mm to 

the right of P3.1

91.5 %

center of screen at the longitudinal 

axis of forklift
19

97 %

right edge of screen at 120 mm to 

the left of P3.2

100 % right edge of screen at P3.2

Test 5 100 % left edge of screen at P4.1

100 %

center of screen at 70 mm away 

from P4.1

100 %

center of screen at 140mm away 

from P4.1

100 %

center of screen at 210 mm away 

from P4.1

100 % right edge of screen at P4.2

Test 6 100 % left end point of screen at P5.1

100 %

midpoint of screen at midpoint of 

P5.1-P5.2

100 % right end point of screen at P5.2

Test 7 100 % left end point of screen at P6.1

100 %

midpoint of screen at midpoint of 

path P6.1-P6.2

100 % right end point of screen at P 6.2

Test 8 100 % right end point of screen at P7.2 

100 %

midpoint of screen at midpoint of 

P7.1-P7.2

100 % left end point of screen at P7.1

Test 9 100 % right end point of screen at P 8.2

100 %

midpoint of screen at midpoint of 

P8.1-P8.2

100 % left end point of screen at P 8.1

Test 10 100 % right end point of screen at P9.2

100 %

midpoint of screen at 70mm away 

from P9.2

100 %

midpoint of screen at 140mm away 

from P9.2

100 %

midpoint of screen at 70mm away 

from P9.1

100 % left end point of screen at P9.1

Test 11 50 % Forklift tines

RESULTS OF ADDITIONAL EXPERIMENTS 

Additional tests beyond ISO/DIS 13564-1 tests were completed by NIST researchers. Each of 

the tests results are explained below. 

1. Use of incandescent lamps instead of halogen lamps
20

Incandescent lamps resulted in unclear lines on the test body where percentage of shadows 

could not be determined. Therefore, no results are shown for this additional test.

2. Use of 13 incandescent and 2 halogen lamps

The two halogen lamps provided additional clarity over the use of only incandescent lamps. 

However, there was no additional information that could be clearly determined without 

complex experimental data from the lights being use at all 13 locations. Therefore, no results 

are shown for this additional test.

3. Use of loads carried by the forklift – tested on human-type test bodies instead of a screen. 

Tests 1, 3, and 4 from ISO/DIS 13564-1 were completed for loads carried by a forklift. 

Table 5 shows the results.

Table 5. Test results with forklift carrying a pallet of boxes. Fork arms height 90 cm, tests with 

four boxes, each 31 cm

3

. Tests 1, 3, 4 are in the forward direction. Tests in other directions were 

not affected by the pallet of boxes. See examples in Figure 10.

Test object Mannequin

1.8 m high

Standard 

Test Number

1 3 4

Test Results Only head could be 

seen 

Only head could be seen Only head could be seen at 

midpoint of path

Test object ANSI B56.5 Standard Test pieces 

(200 mm dia. x 600 mm long and 70 mm dia. x 400 mm high)

Standard 

Test Number

1 3 4

Test Results Could not be seen at 

locations 2 and 3 

Could not be seen Could be seen 
21

Test object Standard Test body

Standard 

Test Number

1 3 4

Test Results 

comparied 

to standard 

tests.

Percentage of 

illuminated area 

dropped from 100 % 

to 21 % 

Percentage of illuminated 

area dropped from 100% to 

21 %

Illuminated area dropped to 

5 % at midpoint of path and it 

dropped to 50 % at location 3 

along path. 

Figure 10: Photos of tests with pallet of boxes (left) using the test board and (right) using a 

mannequin.

Table 6. Results when fork arms were raised to 117 mm above floor. See examples in Figure 11.

Test object Mannequin

Test Number 1 3 4

Test Results Only feet and head 

could be seen along 

test path

Only feet and head could 

be seen along test path

Head and legs could be seen 

at midpoint of path. Entire 

mannequin could be seen 

elsewhere 
22

Test object ANSI B56.5 Standard Test pieces 

(200 mm dia. x 600 mm long and 70 mm dia. x 400 mm high)

Test Number 1 3 4

Test Results Could be seen Could be seen Could be seen along path

Test object Standard Test body

Test Number 1 3 4

Test Results

Compared to 

standard 

tests

Illuminated area 

dropped from 100% 

to 42% along path

Illuminated area dropped 

from 100% to 42% along 

path

Illuminated area dropped to 

85% when test body was 

located at midpoint of path, 

at location 3, and at location 

5, respectively. 

Figure 11. Shadows on the test screen when fork arms were raised to 117 cm
23

RECOMMENDED IMPROVEMENTS TO CURRENT STANDARDS

ISO/DIS 13564-1 and ANSI/ITSDF B56.11.6

1. Change to the simulation of operator eyes. 

Since turning on all the lights at the same time did not effectively simulate the positions of 

two eyes of an operator, a change to the current method can be introduced and tested. Two 

lamps separated by 75 mm could be used to approximate the operator‟s eye spacing. The 

average human eye separation, as found in online web searches, is 65 mm. [6] Therefore, to 

simulate the two eyes of an operator, only two lamps (3 and 5) were turned on. To better 

simulate the movement of the head of an operator, the entire light source array was rotated 

from +45° to -45°. The two shadows at the same location P1.1 were compared when 

generated by the standard stationary method and the recommended rotated lamps method.

The resulting illuminated area according to the standard method was 100 %. However, the 

illuminated area dropped to 0 % when the light source array was rotated to -30°. This meant 

that there was a blind spot that could not be detected by the standard method and therefore, 

by the operator. Figures 12 shows photos of shadows on the test screen when following the 

standard and also shadows on a mannequin. Figure 13 shows the same scene after rotating 

the lights -30°. 

Figure 12 Shadows by following standard: (left) on a test board as specified in the standard, 

(right) using a mannequin instead of the test board.
24

Figure 13. Shadows by rotating light source array -30°: (left) on the test board and (right) using a 

mannequin instead of the test board.

The first suggested change of the standard is, therefore, to rotate the lamp array with only 

two lamps turned on and separated 75 mm.

2. Change to test 3.

Test 3 requires turning on any two lamps separated by 75 mm. The chosen two lamps to 

illuminate for tests can dramatically affect the results where a certain combination of lamps 

may detect non-visible regions and the test may fail. A suggested change to the standard is 

that all combinations of the lamps separated by 75 mm should be tested. Individual switches 

for each light or a sliding mechanism could perhaps allow the two lamps separated by 75mm 

to move as if the operators head moves side to side. 

3. Include tests with underslung loads.

ISO/DIS 13564-1 mandates that the forklift be „unladen‟ (unloaded) during testing. 

However, forklifts are used to carry and deliver loads. Tests were conducted with the forklift 

as if carrying a battery charger as shown in Figure 14 (a). The fork arms were raised and the 

fork frame structure blocked the operator‟s visibility. Three test pieces were used in the test, 

including: test body, mannequin, ANSI/ITSDF B56.5 standard test pieces. When the fork 

arms were raised, the percentage of illuminated area decreased as expected due to additional 

forklift structure blocking lamps. When the fork arms were raised to 117 cm high, 

illuminated percentage of test body dropped from 100 % shown in Figure 14 (b) to 42% as 

shown in Figure 14 (c). Figure 14 (d) shows resulting shadows on a mannequin to interpret 

visibility results for pedestrians and Figure 14 (e) shows similar results as in Figure 14 (c) but 

on a closer test body path to the vehicle. A suggested change to the standard is that visibility 

tests should be tested with the forklift carrying underslung loads.
25

 

a

b c

d e

Figure 14 (a) Forklift with an underslung load used for visibility tests, (b) test body before 

the arms were raised, (c) test body when forklift tines were raised and resulting shadows: (d)

on a mannequin and (e) on the test body at a closer path to the fork tines.
26

4. Include tests with palletized (on-fork tine) loads.

Similar to recommendation 3, recommendation 4 suggests visibility tests also be conducted 

while the forklift carries loads above the fork tines (see Figure 15 (a)), such as a pallet of 

chosen standard-size boxes. Specific load size should be specified. Illuminated area was 0 % 

with the test body at P1.2 as shown in Figure 15 (b). Other visibility test apparatuses were 

also used in NIST tests including a mannequin and ANSI/ITSDF B56.5 standard test pieces

(see Figure 15 (c, d)). Illuminated area was 0 % with the mannequin and 0 % with the test 

pieces when they were located at the midpoint of P3.1 - P3.2. 

a b

c d

Figure 15. (a) Forklift carrying a pallet of boxes for visibility tests with resulting shadows shown 

on: (b) the test body, (c) ANSI/ITSDF B56.5 standard test pieces, and (d) a mannequin.

5. Include tests with a smaller screen.

As in recommendation 4, ANSI/ITSDF B56.5 standard test pieces can go undetected in 

certain cases. These pieces can represent a person‟s lower leg and the midsection or thigh of 

a person lying in the vehicle path. Therefore, a suggested recommendation to visibility 
27

standards is to also use a smaller screen to represent small obstacles along with an 

appropriately safe visibility percentage. A smaller screen with 300 mm x 1000 mm was used 

in the test as shown in Figure 16 (a). With the midpoint of the screen at about 45 mm to the 

right of the midpoint of P1.2 - P1.2, the illuminated area of the original screen was 20 %, but 

the illuminated area of the smaller screen was 0 % where it failed the visibility test. Figure 16

(b) shows that the entire smaller screen is within the shadow thereby demonstrating 0 % 

visibility.

a

b

Figure 16. (a) Standard and smaller sized test screens marked on the board; (b) large screen 

passing the visibility test and the smaller screen failing the visibility test (i.e., fully within the 

shadow).

Standard 

test body

Smaller test 

body
28

6. Specify exact locations of the test screen along test paths.

Locations of the test screen and test body are not exactly presented in the standard and 

provide some ambiguity as to what the exact location should be. Tests proved that test 

screen locations can vary the test results. Therefore, we recommend that the exact locations 

of the test screen and test body be specified to avoid confusion and to compare exact test 

results to other similar forklifts. Should locations vary with respect to the forklift size and 

geometry, it is recommended that varying test screen locations with respect to the forklift be 

required.

7. Inform the reader of a typical type of lamps and their mounts. 

Lamps were relatively expensive ($11 each x 13), difficult to locate, and were eventually 

purchased from an automobile parts store. As a result, a custom slot-type mounting plate 

was designed (see Figure 2) to support the lamps due to their unique shape and spacing 

requirement. The slotted lamp plate also allowed lamps to be moved as in recommendation 2 

to test two lamps, spaced 75 mm apart and mounted in various slots. Therefore, it is 

recommended that the standard provide information of the typical type of lamps, beyond 

stating “halogen or similar,” and how to mount them in the specified array.

8. Specify the danger of using halogen lamps. 

Although halogen lamps provide the ideal sharp edged shadows required by the standard, 

they can be hazardous. Halogen lamps are extremely hot, extremely bright, and require 

relatively high power as compared to standard incandescent light bulbs. Two 

recommendations are therefore: a) to provide a safety discussion in the standard with regard 

to lamp heat, luminescence, and power; b) to list the lamp luminescence in lumens, not watts,

so that potentially safe, lower power or heat lamps can be used for tests and advanced 

technology in light sources can be compared to the 55 W halogen lamps currently specified. 

We also suggest that further research is needed with the use of Light Emitting Diode (LED) 

or other low temperature and low power lamps. 

9. Include advanced visibility measurement test methods. 

Minimal information is provided in visibility standards for an advanced measurement 

solution for powered industrial vehicles. A proposed plan is in place at NIST to collaborate 

with a university to develop test methods for the advanced visibility measurement of

powered industrial vehicles. At least one university has studied construction vehicle 

visibility issues using advanced laser scanning techniques. [11] As these visibility 

measurement techniques evolve for powered industrial vehicles, the standard should reflect 

the usefulness of such systems and how they provide additional benefit. Benefits will 

include measurement time savings, safe test methods, and more accurate and detailed 

measurement and representation of non-visible regions. 
29

Current efforts are being made towards ensuring complete powered industrial vehicle 

operator visibility (see Appendix 3 – Recent visibility efforts) and accurate knowledge of 

sensor type (e.g., 2-dimensional laser detection and ranging verses 3-dimensional light 

detection and ranging) that can ensure safe vehicle operation. Hence, the non-visible regions 

must be clearly represented to advanced technology providers of augmented visibility sensor 

systems on, or soon to be on, the market. Current test methods described in visibility 

standards provide allowable non-visibility percentages from shadows on a movable test body 

creating a piecemeal model of non-visible regions. The methods may be tedious, timeconsuming, and less accurate for industrial vehicle manufacturers to design improvements 

and for augmenting visibility sensor providers to determine sensor type and mounting 

locations for safe 100 % operator visibility. 

ISO 5353: 1995

1. Change the SIP apparatus drawings. 

Separate SIP apparatus component dimensioned drawings into individual drawings and also 

provide an assembly drawing with appropriate tolerances. The SIP apparatus drawing layout 

specified by the standard required potentially unnecessary time and additional materials. 

Drawings that interpreted the standard were additionally required to produce parts. This is 

because X, Y coordinates, as used by machinists for dimension layout and computer 

numerical control input, are not shown in the standard on each piece to be fabricated. See the 

SIP apparatus base drawing on wood in Figure 17 (a). The outside rectangle is the overall 

dimension of the SIP apparatus where several base dimensions are referenced in the standard 

(see Figure 23 of Appendix 1 – Modified SIP Apparatus Design). To produce the drawing 

shown within the Figure 17 (a) rectangle, either the wood must be marked or an additional 

interpretation drawing is required. Other components needed for NIST to make the SIP 

apparatus are shown in Figure 17 (b) and the fully assembled apparatus is shown in Figure 17

(c). Ideally, a base drawing and each other component drawing required are individually 

shown in the standard with an additional assembly drawing showing mounting dimensions

and locations. A photo of a completed system may also be very useful.

Also, tolerances are shown to 0.0 mm and may not be necessary for fabrication and as such,

increase machining and assembly costs.
30

a b

c

Figure 17. (a) SIP Apparatus: (a) base drawn on a piece of wood (b) joining bar for base to back, 

(c) fully assembled apparatus on a forklift seat.

SUMMARY AND CONCLUSIONS

Standard tests for operator visibility when driving forklifts allow for 20 % non-visible regions. 

Some safety technologies are on the market that can help to reduce pedestrian and forklift driver 

injuries. However, large numbers of accidents still occur. Standard tests were performed by 

NIST researchers to provide recommendations to the standard committees on better test methods 

and to provide basis for future NIST industrial vehicle programs. Standard tests provided few 

results that demonstrate the actual non-visible regions of forklifts. Based on the results of the 

testing, there are a number of recommendations to improve these standards including: the use of 
31

low power and temperature lamps; tests that allow lamp placement resembling an operators 

instantaneous eye position; and use of simpler test apparatuses and advanced test methods that 

use lasers that measure exact locations of non-visible regions for improving forklifts and their 

safety. These advanced methods can also allow sensor and vehicle manufacturers to develop onboard vehicle systems to improve operator alerts and semi-autonomous slow and stop controls. 

Advanced 2D and 3D imaging sensors are potentially useful for onboard safety measurement of 

non-visible regions. Future plans are to measure the performance of advanced laser systems used 

to measure non-visible regions of forklifts and to publish results as further recommendations to 

standards committees. Example measurement results of 3D imagers with operator alerts and a 

laser measurement system are shown in Appendix 3 – Recent and planned visibility efforts.

ACKNOWLEDGEMENTS

The authors would like to acknowledge the ANSI/ITSDF B56.11.6 committee who provided 

standards information to perform the tests.

REFERENCES

[1] Roger Bostelman, Will Shackleford, “Advanced Sensing Towards Improved Forklift Safety”, 

PerMIS 2010 Proceedings, Gaithersburg, MD.

[2] ANSI/ITSDF, http://www.itsdf.org/pB56.asp, 2011. 

[3] International Organization for Standardization, http://www.iso.org, 2011.

[4] ISO/DIS 13564-1: 2007 - Powered Industrial trucks – Visibility - Test methods and 

verification-Part 1: Sit-on and stand-on operator trucks and variable reach trucks.

[5] ANSI/ITSDF B56.11.6: 20xx - Evaluation of Visibility from Powered Industrial Trucks.

[6] Bostelman, Roger, 2009. “White paper, Towards Improved Forklift Safety,” PerMIS 2009 

Proceedings, Gaithersburg, MD.

[7] Measurement Science for Intelligent Manufacturing Robotics and Automation Program 

website: http://www.nist.gov/el/isd/si/msimra.cfm, 2011.

[8] ANSI/ITSDF B56.5: 2010 - Safety Standard for Driverless, Automatic Guided Industrial 

Vehicles and Automated Functions of Manned Industrial Vehicles.

[9] ANSI/ITSDF B56.11.6: 20xx - Evaluation of Visibility From Powered Industrial Trucks

[10] ISO 5353: 1995 - Earth-moving machinery, and tractors and machinery for agriculture and 

forestry-Seat Index Point
32

[11] Wolfgang Wieser, “Creating stereoscopic left-right image pairs with POVRay,” 

http://www.triplespark.net/render/stereo/create.html, September 2, 2007.

[12] Jochen Teizer, Ben S. Allread, Uday Mantripragada, “Automating the blind spot 

measurement of construction equipment,” Automation in Construction Journal, Vol. 19 (2010), 

pp. 491–501.
33

APPENDICES

Appendix 1 - Modified SIP Apparatus Design

green outlined parts = NIST machined part adapted to ISO standard – green part 

is 6.4 mm (1/4 in) thick aluminum with wooden blocks added to match standard 

dimensions.

Figure 18. SIP Apparatus drawing showing standard drawing in gray and red, black and green 

modifications for NIST experiments.
34

Appendix 2 - Forklift Test Orientation and Patterns of Shadows

 

a b

 

c d

Figure 19. (a) Top view of lamps test angles as specified by ISO/DIS 13564-1, (b) Lamps rotary 

joint, (c) Lamps facing forward, (d) Lamps facing to the rear of the forklift.

Distance of lights to 

axis of rotation

Lamps

Axis of lamp array 

rotation

0°
35

a

b c

Figure 20. Examples of shadows of visibility tests, from: (a)Test 3, at location 3, (b) test 4, 

location 3, and (c) test 3, location is left edge of test screen at P1.1.
36

Appendix 3 - Recent and planned visibility efforts 

• Performance testing of advanced 3D imagers on test pieces 

• Performance measurement of advanced 3D imagers mounted to forklifts to detect obstacles, 

pedestrians in the NIST lab and in a real manufacturing facility 

• Development of software to integrate 3D imaging with operator alerts (see Figure 20) 

• Georgia Institute of Technology has focused advanced visibility measurements on 

construction vehicle visibility (see Figure 21) [11]. NIST is planning to work with a 

university on advanced visibility measurements for powered industrial vehicles.

a b 

c

Figure 21. 3D imagers mounted on a forklift and integrated with simple operator alerts – (a) 

obstacle is behind the forklift and (b) the alert indicates the obstacle, (c) high lift obstacle detect 

sensor mounted to forks frame (upper right photo) capturing data of ceiling joists (lower left).

Ceiling joist 

being detected 
37

Figure 22. GaTech automatic detection of blind spots for construction dozer (left column) and 

pickup truck (right column) [12]