[Federal Register Volume 63, Number 102 (Thursday, May 28, 1998)]
[Rules and Regulations]
[Pages 29139-29143]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-14110]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-98-3870; Notice 7]
RIN 2127-AG81


Federal Motor Vehicle Safety Standards; School Bus Pedestrian 
Safety Devices

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Final Rule.

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SUMMARY: The agency is amending Standard No. 131, School Bus Pedestrian 
Safety Devices, to permit the use of additional light sources on the 
surface of retroreflective stop signal arms and to permit a certain 
amount of the retroreflective surface to be obscured by mounting 
hardware. It also makes minor clarifications to the standard. This 
responds to a petition from Transpec, Inc., a maker of stop arms.

DATES: This rule will become effective on May 28, 1998. Petitions for 
reconsideration of this rule must be received no later than July 13, 
1998.

ADDRESSES: Petitions for reconsideration should refer to the docket 
number and notice number and be submitted in writing to: Administrator, 
National Highway Traffic Safety Administration, Room 5109, 400 Seventh 
Street, SW, Washington DC, 20590. Telephone: (202) 366-5267

FOR FURTHER INFORMATION CONTACT:
    For technical issues: Mr. Charles Hott, Office of Crashworthiness 
Standards, National Highway Traffic Safety Administration, 400 Seventh 
Street, SW., Washington, D.C. 20590 (202) 366-0247.
    For legal issues: Mr. Paul Atelsek, Office of the Chief Counsel, 
NCC-20, telephone (202) 366-2992, FAX (202) 366-3820.

SUPPLEMENTARY INFORMATION:

1. Background

    Federal Motor Vehicle Safety Standard No. 131, School bus 
pedestrian safety devices requires each new school bus to be equipped 
with a stop signal arm. A stop signal arm is a device, patterned after 
a conventional ``STOP'' sign, that automatically extends outward from 
the bus to alert motorists that a school bus is stopping or has 
stopped.
    To ensure the conspicuity of a stop signal arm, Standard No. 131 
specifies that the device must either be reflectorized or be equipped 
with flashing lamps. If reflectorization is used to comply with the 
standard, ``the entire surface of both sides of the stop signal arm'' 
must be reflectorized (S5.3.1, emphasis added). NHTSA has interpreted 
this language to mean that Light Emitting Diodes (LEDs) outlining the 
word ``Stop'' on the stop arm blade would not be permitted under the 
reflectorization option because LEDs do not meet the requirements for 
reflectorized material.
    Transpec, Inc. (Transpec) submitted a petition for rulemaking 
requesting that S5.3.1 of the standard be amended to allow the use of 
LEDs on stop signal arms. The petition sought to amend the section to 
permit red LEDs on the surface of the stop arm that are ``contained 
within a light channel not greater than 10mm (.394 inches) wide 
centered within the stroke width of each letter.'' Under the requested 
amendment, the minimum stroke width of letters containing LEDs would be 
increased from 20 mm (0.79 inches) to 25 mm (0.8984 inches). The LEDs 
would be required to flash at the rate specified for stop arm lamps 
conforming to S5.3.2. The petition also sought to permit a percentage 
of the surface area of the stop arm to be obscured by mounting brackets 
and other necessary components, with the aggregate area obscured by the 
LEDs and other components not to exceed 7.5 percent of the surface area 
of the stop arm.

2. The Notice of Proposed Rulemaking (NPRM)

    On August 6, 1997, the agency published a NPRM proposing to amend 
the standard in most ways as requested by Transpec. It proposed to 
permit light to be emitted ``from the surface of each letter or from 
the area immediately surrounding each letter'' in the legend ``STOP.'' 
Lamps on the surface of the letter would have to be located on the 
centerline of each letter, or outline each letter of the legend. The 
lamps on the surface of the stop arm would have to flash in the same 
manner as specified for the lamps in non-reflectorized stop arms. The 
net stroke width (i.e., the stroke width minus the width of the legend 
lamps) of each letter containing lamps was proposed to be at least 15 
mm, to assure that an acceptable amount of white letter reflectorized 
surface would be provided.
    Rather than limit the permitted light sources to LEDs, the agency 
was more flexible than requested, proposing to permit almost any type 
of light source in the legend lamps. It proposed to permit white lamps 
as well as red lamps, but not both colors simultaneously, on the 
assumption that

[[Page 29140]]

white lamps might better illuminate the white letters. It also proposed 
amending S6.2.2.1 to eliminate the word ``filament,'' in order to 
permit other non-filament light sources to be used in the legend lamps. 
It also clarified that a requirement on the ``off'' cycle time of 
gaseous discharge lamps applied only to xenon short-arc discharge 
lamps.
    The agency proposed to permit ``mounting brackets, bolts, or other 
components necessary to the mechanical or electrical operation of the 
stop signal arm'' to obscure up to 7.5 percent of the total surface 
area of either side of the stop arm, and up to 10 percent of the white 
border.
    Finally, the NPRM clarified that when two stop arms are installed 
on the same side of a bus, the forward side of the rearmost stop signal 
shall not be reflectorized. This was done to avoid confusing drivers in 
the lanes of opposing traffic as to where they should stop relative to 
the school bus.
    The agency also requested comment on a wide range of issues, 
including: (1) comments and test data about the effectiveness of LED-
equipped stop signal arms as a means of enhancing stop arm conspicuity, 
(2) the use of other light sources, such as miniature incandescent and 
neon light sources, and their effectiveness, and the possibility of 
confusion from mixed light sources, (3) whether to allow use of either 
red or white LEDs or other light sources, or to allow only one color of 
emitted light, (4) whether 7.5 percent, the percentage of permitted 
obscuration requested by Transpec, is an appropriate amount, (5) what, 
if any, intensities and test procedures should be required for lamps 
used on stop arms. In addition, the agency noted that the Society of 
Automotive Engineers' standards referenced in FMVSS 131 are not current 
and asked if it would be useful to update some or all of these to the 
latest versions and if there would be any burden associated with making 
such changes, (6) whether light sources should be allowed to outline 
each letter rather than be centered on each letter, and (7) whether an 
immediate effective date is appropriate.

3. Summary of Comments

    Comments were submitted by sixteen State departments of education 
or school districts, Mr. Harry Gough, P.E., and two stop arm 
manufacturers, Transpec and Specialty Manufacturing. Six of the school 
district comments were forwarded by Transpec. Two national student 
transportation organizations commented, the National School 
Transportation Association (NSTA) and the National Association of State 
Directors of Pupil Transportation Services (NASDPTS).
    The Florida Department of Education conducted a comparative test 
program involving school buses and three stop arm designs: standard 
reflective stop arms with incandescent lights; stop-arms using strobe 
lights; and Transpec LED-equipped stop arms. Fifteen different Florida 
school districts tested the three stop arm designs for 20 school days 
each. Although the results were not statistically significant, the 
Florida study concluded that the LED and the strobe lighted stops were 
``no less effective'' at stopping traffic than the incandescent lighted 
stop arms Florida currently uses. The study also concluded that the raw 
data tend to indicate ``some improvement'' at stopping traffic by both 
the strobe and the LED type stop arms over the incandescent lighted 
stop arm. The strobe lighted stop arm had a ``small advantage'' over 
the LED stop arm at stopping traffic.
    All other commenting States and school districts that had conducted 
pilot tests liked the Transpec LED stop arm. Most stated that it 
reduced the number of illegally passing motorists and was more visible 
than the ``standard'' stop arm, although it was not always clear what 
they were comparing it to.
    Most commenters that addressed the issue supported the idea of 
allowing other light sources. Transpec stated that NHTSA should 
establish performance requirements for other light sources, but that 
NHTSA's consideration of other light sources should not delay the 
implementation of LEDs.
    No commenters objected to the use of other light sources. Transpec 
submitted the only comment to address the potential for confusion 
caused by the LEDs and other light sources. It stated that the 
potential confusion would not be so great as the confusion caused 
between the flashing lights and reflectorized versions already allowed 
by the standard.
    A number of commenters expressed the opinion that only red lights 
should be permitted in or around the legend. NSTA, Transpec and 
Specialty all commented that these lights should be red because red is 
the color that is currently used in all traffic lights that denote that 
the motorist must stop. Transpec stated that white lights do not create 
in a driver the same sense of urgency as red lights. In addition, 
Transpec stated that white lights introduce a third lighting color 
(i.e., red, amber, and white) to the school bus that could detract from 
the ``STOP'' message.
    Two commenters were concerned about the intensity of LEDs. 
Specialty believed that LEDs were less visible when viewed from an 
angle (as when viewed across multiple lanes) and that side angle 
viewing should be studied. It also believed that LEDs are less visible 
when viewed in direct sunlight. In contrast, a school district that had 
pilot tested the LED stop arm believed that LEDs were more effective 
than the incandescent lights in bright sunshine. Specialty provided 
test results showing that LEDs do not pass the light specifications for 
incandescent lamps in Society of Automotive Engineers Recommended 
Practice J1133, School Bus Stop Arms. Mr. Gough also stated that, based 
on testing, LEDs produce only one third the intensity of light as 
incandescent lamps. He stated that NHTSA should establish minimum 
intensity levels for LEDs.
    Transpec indicated that it had developed a prototype LED-equipped 
stop arm with the LEDs outlining the word stop, but that the design was 
flawed because it had a ``Christmas tree'' effect (i.e., appearing as a 
random field of lights distracting the observer and resulting in 
diminished readability). Transpec urged NHTSA not to allow such a 
configuration of lights unless further testing was conducted.
    The only commenter to address the appropriateness of allowing 
obscuration of up to 7.5 percent of the retroreflective surface of the 
stop arm was Specialty. Specialty stated that the proposed 7.5 percent 
figure was too great, and that obscuring more than 2 or 3 percent of 
the retroreflective material would significantly reduce the 
effectiveness of the stop arm because the retroreflective material does 
the work of alerting the motorist.
    Comment was mixed on the appropriateness of obscuring up to 10 
percent of the white border of the stop arm. Specialty believed that 
limiting the border obscurement to 10 percent may cause some difficulty 
in mounting because some stop arms would have to be positioned farther 
outward, which it believes would cause them to protrude so far out from 
the side of the school bus that the bus would exceed the maximum width 
under some State laws. Some states have laws that limit the distance a 
stop arm can extend from the side of a school bus. Requiring that no 
more than 10 percent of the border be obscured would lead to additional 
tooling cost for manufacturers. However, the NSTA stated that 10 
percent was an appropriate maximum.

[[Page 29141]]

4. Discussion

A. Stop Arm Effectiveness

    NHTSA agrees with the commenters who stated that effectiveness 
should be the prime consideration in whether or not to amend the 
standard. NSTA expressed doubt that adding lights would solve the 
problem of illegally passing motorists, but both it and the NASDPTS 
stated that NHTSA should base its decision on ultimate effectiveness. 
All field testing indicates that the Transpec stop arm is at least as 
effective as other stop arms that the agency permits in preventing 
motorists from illegally passing. The agency found the Florida study to 
be the most helpful because it was the largest study to provide 
comparative data.
    Although statistically significant data would be preferable, the 
agency is not constrained from acting without it. The reactions to the 
field tests of the LED-equipped stop arm were positive, and NHTSA 
considers this a sufficient basis on which to act. The Clark County 
(Nev.) School District, for example, has employed over 230 school buses 
equipped with the LED stop arm over the past five months and feels they 
are superior. Considering the positive test results, the agency has 
decided to permit LED-equipped stop arms.

B. Alternative Light Sources

    The agency agrees with Transpec that the standard should not 
prevent other light sources from being used in the legend of the stop 
arm. No commenter opposed other light sources. The agency notes that 
Standard No. 131 is a design standard only to the extent that it 
promotes uniformity. The agency did not propose to allow only LEDs as 
additional light sources, as Transpec's comment implies. Any light 
source that meets the performance requirements of this rule is 
permitted.

C. Intensity of Lights in the Legend

    Specialty and Mr. Gough expressed concern over the lower intensity 
of LEDs and the inability to see them at angles or in bright sunlight, 
and encouraged the agency to set intensity requirements. Transpec also 
suggested that NHTSA set performance standards for light sources other 
than LEDs. However, at this time there are no industry standards for 
the intensity of lights used in the legend of school bus stop arms.
    As stated above, the primary consideration is effectiveness. In the 
field testing, the LEDs that are currently used in the legend of stop 
arms did not appear to have a negative effect on a driver's ability to 
see the extended stop arm. Therefore, the agency does not believe there 
is currently a need to set intensity requirements. NHTSA will monitor 
the situation closely. Should manufacturers offer excessively dim 
lights that do not adequately substitute for the light ``lost'' by 
obscuring the retroreflective material, or excessively bright lights 
that interfere with the drivers' of other vehicles ability to see, the 
agency will consider developing intensity requirements.

D. Color of Light Sources

    The agency finds persuasive the arguments of NSTA, Transpec and 
Specialty that lights in the legend should be red and not white. Red is 
the color that is currently used in all traffic lights that denote that 
the motorist must stop (e.g., brake lights, traffic lights, railroad 
crossing lights). Therefore, the rule has been modified from the 
proposal to state that red is the only light color that is acceptable 
in the legend of school bus stop arms.

E. Amount of Retroreflective Surface That May Be Obscured

    Only Specialty commented on the amount of surface area and white 
border that could be obstructed on a school bus stop arm. The NPRM 
proposed that no more that 7.5 percent of the total surface area be 
obstructed. Specialty questioned whether 7.5 percent was needed, 
stating that no more than 2-3 percent of the total surface area of 
current stop arm designs will be obstructed by the wires and support 
clips running to surface mount lamps. Specialty also suggested that 
permitting the obscuration of 7.5 percent of the reflective surface 
could have a safety impact. It stated that the more retroreflective 
material that is obscured, the less noticeable the stop arm becomes. It 
concluded that obscuring more than 2-3 percent of the retroreflective 
material would significantly reduce the effectiveness of the stop arm.
    During a May 7, 1998 telephone conversation with Specialty's 
Engineering Manager, Specialty revised its position on this issue. It 
referred to an industry-wide market survey of current stop arms showing 
that mounting brackets currently obscure up to 6.3 percent of the 
retroreflective material. Since a small amount of additional 
retroreflective material might be obscured by bolts and other necessary 
components, Specialty now takes the position that permitting up to 7.5 
percent obscuration is appropriate, since it is needed by the industry 
for current designs, and would not significantly reduce the 
effectiveness of the stop arm.
    Ultimately, there was no opposition to permitting 7.5 percent 
obscuration. The market survey referred to by Specialty adds support 
for the proposed amount by indicating that current stop arm designs 
require this provision. Therefore, the proposed 7.5 percent obscuration 
permitted for brackets, bolts, or other components is retained in the 
final rule.

F. Amount of White Border That May Be Obscured

    The amount of white border that may be obstructed proved to be more 
controversial. The NPRM proposed allowing up to 10 percent of this 
border be obstructed. Specialty argued that more of the border should 
be allowed to be obstructed for two reasons.
    First, Specialty attempted to define the role of the white border. 
It argued that the purpose of the white border is to provide a clear 
border definition and an enhanced contrast between the retroreflective 
material and the background (i.e., the area behind the stop arm). 
Specialty concluded that ``the border does not alert [the] motorist to 
the stop arm, the retroreflective material does that.''
    This argument is not persuasive because, as stated in NHTSA's 
November 1, 1995 interpretation to Specialty, the ``entire surface'' of 
the stop arm is required to be reflectorized, including the white 
border. Since the white border is retroreflective, it contributes to 
the light returning to the drivers of other vehicles, while the area 
that NHTSA is allowing to be obstructed does not. As Specialty noted, 
the white border also provides contrast. Therefore, NHTSA also 
considers the border to be important in attracting the motorist's 
attention.
    Second, Specialty argued that stop arms require mounting brackets 
to mount the stop arm to the school bus and the mounting brackets may 
obscure part of the border, and that requiring no more than 10 percent 
of the border to be obscured would lead to additional tooling costs for 
manufacturers to devise methods for putting the stop arm blades further 
outboard without violating State laws.
    This argument is persuasive. It was not the intent of the NPRM to 
change the way existing stop arms are mounted on school buses. The 
intent was to provide a basis for the amount of white border that could 
be obstructed by mounting and operational hardware. Some obscuration is 
a practical necessity for mounting the stop arm blade in a cost-
effective manner. Specialty did not offer the percentage of white 
border that is obstructed on

[[Page 29142]]

current stop arms. Agency staff looked at various models of stop arms 
and concluded that, at most, 15 percent of the white border is 
obstructed by mounting hardware. Therefore, S5.1.2 has been changed to 
permit 15 percent obscuration of the white border.

G. Outlining Versus Centering the Lamps in the Legend

    Transpec was the only commenter to address the issue of placement 
of the lights in or around the legend. Its recommendation against 
placement on the border of the legend was based on its desire to avoid 
a ``Christmas tree effect'' it found in one of its prototypes. As 
stated in NHTSA's November 1, 1995 interpretation letter to Specialty, 
widely spaced lights ``could appear as a random field of lights (like a 
Christmas tree), distracting the observer and resulting in diminished 
readability.'' Transpec therefore recommends restricting light 
placement to a location ``centered'' within the letters.
    The agency notes that this ``Christmas tree effect'' is caused more 
by excessive spacing between adjacent lights than by their placement 
relative to the legend. The effect can also be caused by lights 
centered in the legend's letters, if the spacing between the lights is 
too great. Conversely, the effect can be avoided with lights placed 
around the perimeter of the legend's letters if the lights are located 
close enough together.
    The option for placing the lamps around the border is being 
retained in the final rule. The agency does not believe it is currently 
necessary to regulate the spacing of the lights in or around the 
legend. The optimum spacing might vary according to the lamp intensity, 
lamp size, and legend letter size. NHTSA will monitor the products 
being offered and will consider specifying light spacing if it finds 
stop arms being produced with LEDs that impair the effectiveness the 
stop arm, regardless of whether they are centered in, or arranged 
around the border of, the letters.

H. Effective Date

    Some commenters urged delaying the effective date. Specialty 
recommended that the effective date of these amendments be delayed 
until extensive testing is conducted, out of a concern that pushing 
untested, potentially nonbeneficial technologies quickly to market 
would not be in the interest of the general public. The NSTA, the 
NASDPTS, Mr. Gough, and a few other commenters also encouraged NHTSA to 
conduct extensive testing before promulgating the rule.
    Other commenters, notably Transpec and some States and school 
districts that liked Transpec's stop arm, urged an immediate effective 
date. The primary reason given was that to delay implementation would 
perpetuate confusion and ambiguity over Transpec's LED-equipped stop 
arm and delay arrival of a beneficial technology in the market.
    The agency concludes that an immediate effective date is warranted. 
Field testing indicates that the Transpec stop arm is at least as 
effective as existing stop arms in stopping motorists from illegally 
passing stopped school buses. The commenters who encouraged more 
extensive testing did not have the benefit of the results of the 
Florida study and may not have realized the large number of smaller 
pilot test programs being conducted by the other States and school 
districts when they composed their comments. The agency considers this 
field testing to be sufficient.
    This amendment is permissive only, so there is no burden associated 
with an immediate effective date. Since the LED-equipped stop arms seem 
effective, there is no reason to delay their entry into the 
marketplace.
I. Miscellaneous issues
    There was no comment on several aspects of the proposal, and these 
elements are maintained in the final rule. These include: (1) the 
proposal to use a diminished ``net stroke width'' of the letters in the 
legend to account for the width of the lights centered within them; (2) 
the removal of the word ``filament'' in S6.2.2.1 to remove the 
restriction against non-filament light sources; (3) the addition of the 
words ``xenon short arc'' clarification that the requirements of 
S6.2.2.2 apply only to that type of gaseous discharge lamp; and (4) the 
addition of a requirement in S5.3.1.3 that the forward side of the 
rearmost stop signal not be reflectorized if there are forward and 
rearward stop arms.

Regulatory Analyses and Notices

A. Executive Order 12866 (Federal Regulation) and DOT Regulatory 
Policies and Procedures

    This notice was not reviewed under Executive Order 12866, because 
the Office of Management and Budget determined that it is not 
significant within the definitions of the Executive Order. NHTSA has 
analyzed this rulemaking and determined that it is not significant 
within the meaning of the Department of Transportation regulatory 
policies and procedures. The agency has determined that the economic 
effects of the amendment would be so minimal that a full regulatory 
evaluation is not required. Since the amendment would impose no new 
requirement but simply would allow for an alternative design, there are 
no cost impacts. Because stop arms with legend lamps are optional, the 
agency assumes those companies availing themselves of the option would 
be maximizing benefits with respect to any added costs associated with 
legend lamps.

B. Regulatory Flexibility Act

    In accordance with the Regulatory Flexibility Act, NHTSA has 
evaluated the effects of this rulemaking on small entities. Based on 
this evaluation, I certify that the amendment will not have significant 
economic impact on a substantial number of small entities. Accordingly, 
a regulatory flexibility analysis has not been performed.
    The following is NHTSA's statement providing the factual basis for 
certification (5 U.S.C. 605(b)). Because Standard No. 131 applies to 
vehicles rather than stop arms as items of motor vehicle equipment, the 
rule applies primarily to school bus manufacturers. The school bus 
industry is dominated by two companies that are not small entities, but 
there are a few school bus manufacturers that are small entities. All 
school buses are required to be equipped with stop arms. However, this 
rule imposes no requirements, but merely allows school bus 
manufacturers to have more choice in the stop arm designs they order. 
The rule is thus beneficial to vehicle manufacturers, and has no 
negative economic impact.
    All stop arm manufacturers known to the agency are small entities. 
They might be affected in the sense that market share might shift among 
them if school bus manufacturers choose to purchase stop arms with 
legend lights. Transpec is the only company known by the agency to 
produce stop arms with legend lamps. However, NHTSA does not know if 
Transpec's design will be widely accepted in the marketplace, either by 
school bus manufacturers for installation on new buses, or in the 
aftermarket. In addition, this rule provides flexibility for other 
manufacturers to produce their own legend lamp-equipped stop arm 
designs. Therefore, the agency does not view this rule as either 
conferring a competitive advantage or imposing a negative impact on any 
stop arm manufacturer.

C. Federalism Assessment

    This action has been analyzed in accordance with the principles and 
criteria contained in Executive Order

[[Page 29143]]

12612. NHTSA has determined that the rulemaking does not have 
sufficient federalism implications to warrant the preparation of a 
Federalism Assessment. This rule does not impose any unfunded mandates 
on State, local, or tribal governments as defined by the Unfunded 
Mandates Reform Act of 1995 (2 U.S.C. 1532-38).

D. Civil Justice Reform

    This rule has no retroactive effect. Under 49 U.S.C. 30103, 
whenever a Federal motor vehicle safety standard is in effect, a State 
may not adopt or maintain a safety standard applicable to the same 
aspect of performance which is not identical to the Federal standard, 
except to the extent that the state requirement imposes a higher level 
of performance and applies only to vehicles procured for the State's 
use. 49 U.S.C. 30161 sets forth a procedure for judicial review of 
final rules establishing, amending or revoking Federal motor vehicle 
safety standards. That section does not require submission of a 
petition for reconsideration or other administrative proceedings before 
parties may file suit in court.

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber 
products, Tires.
    In consideration of the foregoing, 49 CFR part 571 is amended as 
follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

    1. The authority citation for part 571 continues to read as 
follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50

    2. Section 571.131 is amended by revising S5.2.1, S5.2.2, S5.3.1, 
S6.2.2.1, and S6.2.2.2, and by adding S5.3.1.1, S5.3.1.2, and S5.3.1.3 
to read as follows:


Sec. 571.131  Standard No. 131, School Bus Pedestrian Safety Devices.

* * * * *
    S5.2.1  The stop signal arm shall have a white border at least 12 
mm (0.47 inches) wide on both sides, except as provided in S5.2.3. 
Mounting brackets, clips, bolts, or other components necessary to the 
mechanical or electrical operation of the stop signal arm may not 
obscure more than 15 percent of the border on each side of the stop 
arm. The portion of the border that may be obscured is in addition to 
that portion which may be obscured by the two red lamps specified in 
S5.3.2.
    S.5.2.2  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.
* * * * *
    S5.3.1  Except as provided in S5.3.1.1, S5.3.1.2, or S5.3.1.3, the 
entire surface of both sides of each stop signal arm shall be 
reflectorized with Type III retroreflectorized material that meets the 
minimum specific intensity requirements of S6.1 and Table I.
* * * * *
    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.
* * * * *
    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.
* * * * *
    Issued: May 22, 1998.
Ricardo Martinez,
Administrator.
[FR Doc. 98-14110 Filed 5-22-98; 3:07 pm]
BILLING CODE 4910-59-P