Kerry Legg, Safety & Compliance Manager

Customer Services Head Office

New Flyer, Inc.

25 DeBaets Street

Winnipeg, Manitoba

R2J 4G5 Canada


Dear Mr. Legg:


This responds to your letter asking about the requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment.  You ask whether it would be permissible to incorporate flashing applications of otherwise steady-burning lamps, or add additional special functioning lamps, for emergency conditions on a transit bus.  According to the information you supplied, these lamps would be part of a “silent alarm” system, perhaps used in conjunction with a GPS or radio alarm system, which would notify outsiders or law enforcement to the presence of an emergency situation on the bus without alerting the individual(s) who may be causing a threat inside the vehicle.  After considering the information you provided and the analysis discussed below, we regret to inform you that the silent alarm system you have described with flashing clearance or other special lamps would not be permitted by FMVSS No. 108.


By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment.  Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture.  NHTSA selects a sampling of new vehicles and equipment each year to determine their compliance with applicable FMVSSs.  If our testing or examination reveals an apparent noncompliance, we may require the manufacturer to remedy the noncompliance, and may initiate an enforcement proceeding if necessary to ensure that the manufacturer takes appropriate action.


Analysis of the Silent Alarm Lamps under Paragraph S5.5.10


The question of which lamps are permitted to flash on a vehicle is addressed in paragraph S5.5.10 of FMVSS No. 108.  The relevant provision states:

The wiring requirements for lighting equipment in use are:
(a)   Turn signal lamps, hazard warning signal lamps, and school bus warning lamps shall be wired to flash;
(b)   Headlamps and side marker lamps may be wired to flash for signaling purposes;
(c)   A motorcycle headlamp may be wired to allow either its upper beam or its lower beam, but not both, to modulate from a higher intensity to a lower intensity in accordance with section S5.6;
(d)   All other lamps shall be wired to be steady-burning.

As you correctly point out in your letter, paragraph S5.5.10(d) of the standard supplies the general rule.  All lamps are required to be steady-burning unless specifically excepted by S5.5.10(a)-(c).  Therefore, any lamp not covered by these exceptions cannot flash under any circumstances.  You specifically ask whether clearance lamps are permitted to flash.  Clearance lamps do not fall under any exception enumerated in S5.5.10 (a) through (c). Accordingly, clearance lamps must be steady burning and cannot flash.[1]


Paragraph S5.5.10(b) does permit headlamps and side marker lamps to be wired to flash for signaling purposes.  However, we do not believe that the silent alarm system constitutes “signaling purposes” for the purpose of S5.5.10(b).  We do not believe that the phrase “signaling purposes” should be interpreted in its broadest possible context, which could mean any information communicated to others via visual signals.  Instead, we interpret the phrase “signaling purposes” to be limited to those signals communicating traffic information.[2]  The silent alarm, however, does not signal traffic information, but rather information regarding the duress of the driver.  We believe that extending our interpretation of “signaling purposes” could conflict with the intent of S5.5.10(d), which is to limit the use of flashing lamps on vehicles to a limited and easily-understandable set of signals.  Therefore, a silent alarm system utilizing flashing headlamps and side marker lamps would not be permitted under FMVSS No. 108. 


Under S5.5.10(a), turn signal lamps and hazard warning signal lamps must be wired to flash.  Therefore, S5.5.10 would not prohibit the use of those lamps as part of a silent alarm system.  However, we note that the lamps must still conform to the requirements listed in Table III of FMVSS No. 108.


Analysis of Silent Alarm Lamps under Paragraph S5.1.3


While Standard No. 108 mandates the installation and design of required lamps, it does not prohibit the installation of auxiliary lamps.  However, the use of auxiliary lamps is subject to the restriction in paragraph S5.1.3 (as well as the general prohibitions on flashing lamps in S5.5.10(d)).  Paragraph S5.1.3 reads:


S5.1.3  No additional lamp, reflective device or other motor vehicle equipment shall be installed that impairs the effectiveness of lighting equipment required by this standard.


As you have not provided the specific designs and locations of the auxiliary lamps you are considering, we will provide some examples of “interference” with required lamps. 


“Off-color” lamps, such as red lamps in the front of a vehicle, would be considered to interfere with the standardization of highway signals set forth by Standard No. 108.[3],[4]


Lamps that distort established patterns, such as the three-lamp identification cluster, would be prohibited by Standard No. 108.[5]


Auxiliary lamps that are close to required lamps, and whose glare may obscure the required lamps, would be prohibited under Standard No. 108.[6]


In addition, lamps that communicate non-standard signals are generally prohibited under Standard No. 108.[7]


“Emergency Circumstances”


You also suggest that silent alarm applications, even if they use non-compliant lamps, may meet the “spirit of the regulation” because they are only used in emergency circumstances.  We cannot concur with this interpretation.  Your alarm system must meet the requirements of FMVSS No. 108.  While some police and other emergency vehicles have emergency lighting systems involving flashing lamps, we do not permit these systems on other vehicles.  NHTSA determined that “the drivers that operate police vehicles will be instructed to use the warning system only under certain circumstances,” and permitted the system “because of the circumstances which are unique to law enforcement.”[8] 


Aftermarket Considerations


In your letter, you also requested a waiver, permitting manufacturers to install your system in existing vehicles.  The modification of existing vehicles is regulated by Section 30122 of the Safety Act, which states:


A manufacturer, distributor, dealer, or motor vehicle repair business may not knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard prescribed under this chapter…


If one of these entities listed in § 30122 were to install lighting equipment that resulted in the vehicle no longer meeting S5.5.10, S5.1.3, or any other portion of FMVSS No. 108, then the entity would be in violation of § 30122.  We do not issue waivers from the responsibility entities have to meet under FMVSS No. 108.


If you have any further questions, please contact Ari Scott of my staff at (202) 366-2992.


Sincerely yours,




                                                                        Anthony M. Cooke

                                                                        Chief Counsel






[1] We note that this would not prevent the combination of a clearance lamp with an auxiliary turn signal lamp, as long as the auxiliary turn signal lamp did not impair the effectiveness of the required clearance lamp.

[2] We note that this interpretation of “signaling purposes” is not limited to turn signals, but extends to traffic signals generally.  See 1996 letter of interpretation stating that headlamps that flashed when the horn was activated were compliant with paragraph S5.5.10(b).  August 30, 1996 letter to Julius Fischer, Esq., available at

[3] See, e.g., 11/16/99 letter to Mr. Terry W. Wagar, analyzing various supplementary lamp proposals using amber and red lamps in different locations on a vehicle.  It is available at

[4] We note that this system would also be subject to State law. Furthermore, with respect to using various colored lamps, States reserve the use of the color blue for emergency vehicles. Increasingly, the color purple is used to designate funeral processions.

[5] See 7/28/05 letter to Robert M. Clarke, available at

[6] See, e.g., 4/8/98 letter to Mr. Michael Krumholz, available at

[7] See 4/14/97 letter to Mr. Jack Z. Zhang, stating that a lamp has “the potential to cause confusion for the very reason that it is unique.”  This letter also addresses the issue of aftermarket considerations.  It is available at

[8] See 7/30/2001 letter to Mr. Larry Hughson, available at