(2)
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S5.2.2 The stop signal arm shall have
the word "STOP" displayed in white upper-case letters on both
sides, except as provided in S5.2.3. The letters shall be at least 150 mm
(5.9 inches) in height. The letters shall have a stroke width of at
least 20 mm (0.79 inches), except as provided in S.5.3.1.1.
S5.2.3 When two stop signal arms are installed on a school bus,
the rearmost stop signal arm shall not contain any lettering, symbols,
or markings on the forward side.
S5.3 Conspicuity. The stop signal arm shall comply with either
S5.3.1 or S5.3.2, or both.
S5.3.1 Except as provided in S5.3.1.1, S5.3.1.2, or S5.3.1.3,
the entire surface of both sides of the stop signal arm shall be reflectorized
with type III retroreflectorized material that meets the minimum specific
intensity requirements of S6.1 and Table 1.
S.5.3.1.1 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 immediately surrounding each letter. Only red lamps may
be used. They shall form the complete shape of each letter of the legend,
and shall be affixed to all letters (or to the areas immediately surrounding
all letters) in the legend. The shape of each letter shall remain constant
and, if the lamps are contained within each letter, the net stroke width
(stroke width minus the width of the lamp(s)) of each letter of the legend,
specified in S5.2.2, shall not be less than 15 mm (0.59 inch). When the
stop arm is extended, the lamps shall flash at the rate specified in S6.2.2,
with a current ``on'' time specified in S6.2.2.1. 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.
S5.3.1.2 Nonreflectorized mounting brackets, clips, bolts, or other components
necessary to the mechanical or electrical operation of the stop signal
arm shall not obscure more than 7.5 percent of the total surface area
of either side of the stop signal arm.
S5.3.1.3 When two stop signal arms are installed on a school bus, the
forward side of the rearmost stop signal arm shall not be reflectorized.
S5.3.2 Each side of the stop signal arm shall have at least two
red lamps that meet the requirements of S6.2. The lamps shall be centered
on the vertical centerline of the stop arm. One of the lamps shall be
located at the extreme top of the stop arm and the other at its extreme
bottom.
S5.4 The stop signal arm shall be installed on the left side of
the bus.
S5.4.1 The stop signal arm shall be located such that, when in
the extended position:
(a) The stop signal arm is perpendicular to the side of the bus, plus
or minus five degrees;
(b) The top edge of the stop signal arm is parallel to and not more
than 150 mm (6 inches) from a horizontal plane tangent to the
lower edge of the frame of the passenger window immediately behind the
driver's window; and
(c) The vertical centerline of the stop signal arm is not less than
230 mm (9 inches) away from the side of the school bus.
S5.4.2 A second stop signal arm may be installed on a school bus.
That stop signal arm shall comply with S5.4 and S5.4.1.
S5.5 The stop signal arm shall be automatically extended in such
a manner that it complies with S5.4.1, at a minimum whenever the red signal
lamps required by S5.1.4 of TSD Standard No. 108
are activated, except that a device may be installed that prevents the
automatic extension of a stop signal arm. The mechanism for activating
the device shall be within the reach of the driver. While the device is
activated, a continuous or intermittent signal audible to the driver shall
sound. The audible signal may be equipped with a timing device requiring
the signal to sound for at least 60 seconds. If a timing device is used,
it shall automatically recycle every time the service entry door is opened
while the engine is running and the manual override is engaged.
S6.1 Reflectivity Test. When tested under
the conditions specified in S6.2 (b), (c), and (d) of Federal motor vehicle
safety standard 125, Warning Devices, (49 CFR 571.125), the retroreflective
materials shall meet the criteria specified in Table 1.
TABLE 1 — MINIMUM SPECIFIC INTENSITY PER
UNIT AREA
(cd/lx/m2) (Candela per Foot-candle per Square
Foot)
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
|
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S6.2 Lighting Tests
S6.2.1 Color. The procedure shall be done in accordance with the
Society of Automotive Engineers (SAE) J578, Color Specification (May
1988), 1990 SAE Handbook, Society of Automotive Engineers, Inc. Along
with the incorporation by reference in S6.2.3, this incorporation by reference
was approved by the Director of the Federal Register in accordance with
5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from
the Society of Automotive Engineers, 400 Commonwealth Drive, Warrendale,
PA 15096-0001. Copies may be inspected at Docket Room, National
Highway Traffic Safety Administration, 400 Seventh Street, S.W., Washington,
DC 20590 or at the Office of the Federal Register, 1100 L Street, N.W.,
room 8401, Washington, D.C. When visually compared to the light
emitted from a filter/source with a combination of chromaticity coordinates
as explained in SAE J578, Color Specification (May 1988), within
specific boundaries [y = 0.33 (yellow boundary) and y = 0.98 - x
(purple boundary)] the color of light emitted from the test object shall
not be less saturated (paler), yellower, or purpler. The test object shall
be placed perpendicular to the light source to simulate lamps on stop
signal arms. In making visual comparisons, the light from the test object
shall light one portion of a comparison field and the light from the filter/source
standard shall light an adjacent area. To make a valid visual comparison,
the two fields to be viewed shall be of near equal luminance.
S6.2.2 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 minute.
S6.2.2.1 Lamps, except those subject
to S6.2.2.2, shall have a current "on" time
of 30 to 75 percent of the total flash cycle. The total current "on"
time for the two terminals shall be between 90 and 110 percent of
the total flash cycle.
S6.2.2.2 Xenon short-arc
gaseous discharge lamps shall have an "off" time before each
flash of at least 50 percent of the total flash cycle.
S6.2.3 Vibration, Moisture, Dust, Corrosion, Photometry, and Warpage
Tests. The procedure shall be done in accordance with the Society
of Automotive Engineers (SAE) J575, Tests for Motor Vehicle Lighting
Devices and Components, (July 1983) and Society of Automotive Engineers
(SAE) J1133, School Bus Stop Arm, (April 1984), 1990 SAE Handbook,
Society of Automotive Engineers, Inc. Lamps and lighting components shall
meet the criteria for vibration, moisture, dust, corrosion, photometry,
and warpage in SAE J575, Tests for Motor Vehicle Lighting Devices and
Components, (July 1983) and SAE J1133, School Bus Stop Arm,
(April 1984), under the test conditions specified herein.
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