واﻟ واﻟ  ﻟﻠ  اﻟ  اﻟﻬ 
Saudi Standards, Metrology and Quality Org. (SAS O) 
 
 
 
  
 
 
 
 
 
 
 
Final Draft Standard   
 
 
 
  
SASO /FDS/31830/2020  
  
 
  
 
School buses - Pedestrian safety devices 
 
 
  
 
  
 
  
 
  
 
 
ICS: 43.080.20 
 
This document is a draft Saudi S tandard circulated for comments . It is, therefore, 
subject to alteration and modification and may not be referred to as a Saudi 
Standard until approved by SASO . SASO S TANDAR D   SASO/FDS 31830/2020
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Conte nts 
 
1- Scope ............................................................... ............................................................... ........ 2 
 
2- Terms and definitions ............................................................... .......................................... 2 
 
3- Technical requirements  ............................................................... ..................................... 2 
 
4- Test procedures  ............................................................... ................................................... 4 
 
 
Bibliography   ............................................................. ...............................................................  7 SASO S TANDAR D   SASO/FDS 31830/2020
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School buses - Pedestrian safety devices 
 
 
1- Scope 
This standard specifies the technical requirements and test pro cedures for devices that can be 
installed on school buses to maintain the safety of pedestrians  in the vicinity of stopped school 
buses. 
 
 
2- Terms and definitions 
For the purposes of this standard, the following terms and defi nitions are applied: 
2.1 School bus 
A specially constructed vehicle that is designed to carry more than ten persons to and from 
school, university or related events. 
2.2 Stop signal arm  
A device that can be extended outward from the side of a school  bus to provide a signal to other 
motorists not to pass the bus because it has stopped to load or  discharge passengers. 
2.3 Reflex reflective 
Reflective of light in directions close to the direction of inc ident light, over a wide range of 
variations in the direction of incident light. 
2.4 Observation angl e 
The angle having as its sides the line from the observation poi nt to the center of the object to 
be tested and the line from the  center of that object to the ce nter of the source of illumination. 
2.5 Entrance angle 
The angle having as its sides the line through the center, and normal to the face, of the object 
to be tested, and the line from the center of the object to the  center of the source of illumination. 
 
 
3- Technical requirements 
Each school bus shall be equipped with a stop signal arm as sho wn in figure (1) that meet the 
following requirements: 
3.1 Shape 
3.1.1  The stop signal arm shall be a regular octagon which is at lea st 450 × 450 mm in diameter. 
3.1.2  The word “STOP” letters shall be at least 150 mm in height and  the letters shall have a 
stroke width of at least 20 mm, except as provided in 3.3.1.1. 
3.2 Color 
3.2.1 The stop signal arm shall be red on both sides, except: 
a) The stop signal arm shall have a white border at least 12 mm w ide on both sides, except as 
provided in (c). 
b) The stop signal arm shall have the word “STOP” displayed in bo th Arabic and English 
languages and shall be white upper-case letters on both sides, except as provided in (c). 
c) When two stop signal arms are installed on a school bus, the r earmost stop signal arm shall 
not contain any lettering, symbols, or markings on the forward side. 
3.2.2  Mounting brackets, clips, bolts, or other components necessary  to the mechanical or 
electrical operation of the stop signal arm may not obscure mor e than 15 % of the border on 
each side of the stop arm. SASO S TANDAR D   SASO/FDS 31830/2020
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3.3 Conspi cuity 
The stop signal arm shall comply with either 3.3.1 or 3.3.2, or  both. 
3.3.1  The entire surface of the stop signal arm on both sides shall be provided with Type III 
reflectorized material that meet the minimum specific intensity  requirements according to item 
4.1 and table (1), except: 
3.3.1.1  The legend of the retroreflective stop arm may be illuminated in a manner such that light 
is emitted from the surface of each letter or from the area imm ediately surrounding each letter, 
as follows: 
a) Only red lamps may be used; 
b) They shall form the complete shape of each letter of the legen d, and shall be affixed to all 
letters (or to the areas immediately surrounding all letters) i n the legend; 
c) The shape of each letter shall remain constant and, if the lam ps are contained within each 
letter, the net stroke width (stroke width minus the width of t he lamp(s)) of each letter of the 
legend, specified in 3.2 (b), shall not be less than 15 mm; d) When the stop arm is extended, the lamps shall flash at the ra te specified in 4.2.2, with a 
current “on” time specified in 4.2.2.1; and 
e) All lamps shall be positioned in one of the two following ways : 
1) Centered within the stroke of each letter of the legend, or 
2) Outlining each letter of the legend. 
3.3.1.2  When two stop signal arms are installed on a school bus, the f orward side of the rearmost 
stop signal arm shall not be reflectorized. 
3.3.1.3  Non-reflectorized mounting brackets, clips, bolts, or other co mponents necessary to the 
mechanical or electrical operation of the stop signal arm shall  not obscure more than 7.5 % of 
the total surface area of either side of the stop signal arm. 
3.3.2  Each side of the stop signal arm shall have at least two red l amps that meet the 
requirements of item 4.2, as follows: 3.3.2.1  The lamps shall be centered on the vertical centerline of the stop arm. 
3.3.2.2  One of the lamps shall be located at the extreme top of the st op arm and the other at its 
extreme bottom. 
 
 
3.4 Position 
3.4.1  The stop signal arm shall be installed on the left side of the  bus. 
3.4.2  The stop signal arm shall be located when in the extended posi tion as follow: 
a) The stop signal arm is perpendicular to the side of the bus, p lus or minus five degrees; 
b) The top edge of the stop signal arm is parallel to and not mor e than 152.4 mm from a 
horizontal plane tangent to the lower edge of the frame of the passenger window immediately 
behind the driver's window. 
c) The vertical centerline of the stop signal arm is not less tha n 228.6 mm away from the side 
of the school bus. 3.4.3  A second stop signal arm may be installed on a school bus, and  shall meet the requirements 
of item 3.4.1 and 3.4.2. SASO S TANDAR D   SASO/FDS 31830/2020
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3.5 Operation 
The stop signal arm shall be automatically extended with the pa ssenger door open according to 
the following: 
3.5.1  The mechanism for activating the device shall be within the re ach of the driver. 
3.5.2  While the device is activated, a continuous or intermittent si gnal audible to the driver shall 
sound. 3.5.3  The audible signal shall be equipped with a timing device requ iring the signal to sound 
for at least 60 seconds. 3.5.4  If a timing device is used, it shall automatically recycle eve ry time the service entry door 
is opened while the engine is running and the manual override i s engaged. 
 
 
 
 
 
Figure (1) – characteristic of stop signal device  
 
 
4- Test procedures 
4.1 Reflectivity Test 
The retroreflective materials shall meet the criteria specified  in table (1) when tested under the 
conditions specified in 6.2 (b), (c), and (d) of standard(1). 
 
 
 
  
 
  
 
 
(1) Follow the standard 49 CFR 571.125 until the Saudi standard is adopted.SASO S TANDAR D   SASO/FDS 31830/2020
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4.2 Lighting Tests 
4.2.1 Color 
a) The test procedure shall be done in accordance with standard(2). 
b) When visually compared to the light emitted from a filter/sour ce with a combination of 
chromaticity coordinates as explained in standard(2) within specific boundaries; 
[y = 0.33 (yellow boundary) and y = 0.98 - × (purple boundary)]  
The color of light emitted from the test object shall not be le ss saturated (paler), yellower, or 
purple. c) The test object shall be place perpendicular to the light sour ce to simulate lamps on stop 
signal arms. 
d) In making visual comparisons, the light from the test object s hall light one portion of a 
comparison field and the light from the filter/source standard shall light an adjacent area. 
e) To make a valid visual comparison, the two fields to be view s hall be of near equal 
luminance. 
4.2.2 Flash 
rate 
The lamps on each side of the stop signal arm, when operated at  the manufacturer's design load, 
shall flash alternately at a rate of 60 to 120 flashes per minu te. 
4.2.2.1  Lamps except those subject to 4.2.2.2, shall have a current “o n” time of 30 to 75 % of 
the total flash cycle (except Xenon short-arc gaseous discharge  lamps). 
The total current “on” time for the two terminals shall be betw een 90 and 110 % of the total 
flash cycle. 
4.2.2.2  Xenon short-arc gaseous discharge lamps shall have an “off” ti me before each flash of at 
least 50 % of the total flash cycle. 
4.2.3 Vibration, Moisture, Dust, Corrosion, Photometry, and Warpage Tests 
a) The test procedure shall be done in accordance with standard(3). 
b) The lamps and lighting components shall meet the criteria for vibration, moisture, dust, 
corrosion, photometry, and warpage standards with standards(3) under the test conditions 
specified herein. 
 
 
 
  
 
  
 
  
 
  
 
  
 
 
 
(2) Follow the standard No. SAE J578 until the Saudi standard is ad opted. 
(3) Follow the two standards No. SAE J575 and SAE J1133 until the S audi standard is adopted. SASO S TANDAR D   SASO/FDS 31830/2020
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Observation Angle 
 
(°) Entrance Angle
 
(°) White  Red 
Type III Retroreflective Element Material 
A - Glass Bead Retroreflective Element Material 
0.2 -  4 250 45 
0.2 +  30 150 25 
0.5 -  4 95 15 
0.5 +  30 65 10 
B - Prismatic Retroreflective Element Material 
0.2 -  4 250 45 
0.2 +  30 95 13.3 
0.5 -  4 200 28 
0.5 +  30 65 10 
 
Table 1 - Minimum Specific Intensity per  Unit Area (SIA) 
(Candelas per Foot-candle  per  Square Foot)  SASO S TANDAR D   SASO/FDS 31830/2020
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Bibliography  
 
 
[1] 49 Subtitle B-Chapter V-Part 571-Subpart B Section 131 
(FMVSS 571.131) "School bus pedestrian safety devices".