July 16, 2008
To: Trailer, RV, and Truck Manufacturers
From: Dennis G. Moore, President
I’ve recently sent the attached writing to both
NATM* and NMMA** Legal Departments as I have reason to believe their “Certifying
Inspectors” have been misleading Trailer and RV Manufacturers as to the
“Interpretation” sections of Federal Motor Vehicle Safety Standard #108 (FMVSS
#108) that regulate mandated “Clearance Light” Positioning and
*National Association of
Trailer Manufacturers **National Marine Manufacturers Association
Also, the subject of “Optical Combinations”
seem to be a subject “not clear” to NMMA and NATM Certifying Inspectors
nor to most Trailer and RV Manufacturers as well.
I know both these subjects suffer from long term
misunderstandings and confusion, and I also know that NHTSA makes no
attempt to clarify these subjects … so confusion and mandate
violations continue, spurred on with a “let it rip” NHTSA attitude
that’s resulting in Trailer, RV, and Truck Manufacturers … as well as
Aftermarket Replacement Distributors … being led into decreasing the safety of
their vehicles while increasing their public liability exposure.
All this chaos while NHTSA employees remain oblivious and immune to any
liability using their usual “hide behind” and “back and fill” excuses.
In any case … I’ve tried to clarify the “Clearance”
Light and “Optical Combination” subjects with the attached
If read carefully while comparing each confusing detail to
the latest FMVSS #108 printing on
NHTSA.gov … and asking NHTSA’s Legal Counsel division for “Legal
Interpretations* “ when needed … can eventually result in a full understanding
of the actual Intent of the 1966 Vehicle Safety Act and … hopefully help to
clarify the resultant FMVSS #108 Mandates.
We hope you take this opportunity to try and learn about
these subjects in detail so you can make safer vehicles at less cost and perhaps
better appreciate our quality, safety features, and overall value when compared
to cheapened Chinese Copies and (twice the $ cost) Multi-Function LEDs that are
beginning to generate leaking and failure “returns” that are turning happy
profit situations into $ loss and grief ridden situations.
Home of DRY LAUNCH® and
CONVOY® Quality Vehicle Lighting Products
July 16, 2008
“TECHNICAL & LEGAL CLARIFICATIONS” – 2008
FMVSS #108* “CLEARANCE”
and “OPTICAL COMBINATION” Clarifications
*Federal Motor Vehicle
Safety Standard #108
Dennis G. Moore, Sierra
Design Manufacturing, Inc.
(Formerly Sierra Products,
Inc.) Livermore &
Everyone answerable to
Trailer, RV and Truck Federal Lighting Laws should consider the following:
About “CLEARANCE LIGHTS”
Clearance Lights must be mounted … “as close as practical” to
“represent the extreme width”* of the Vehicle. Contrary to popular
beliefs … there is no Federal “Legal Interpretations” on record
that Carte Blanc allows up to 6” mountings of Clearance Lights inboard of the
Extreme Width. Study the three
attached NHTSA Legal Interpretations and also consider checking our other
writings on this subject on our DryLaunch.com website.
“Extreme Width” is used interchangeably with “Overall Width” by
D.O.T. and NHTSA
The 6” inboard
mounting discussed in the attached NHTSA “Interpretations”
still is required to comply to the “as close as practical to represent the
extreme width mandate”. These Interpretations verifies the fact that
mounting Clearance Lights “not” at the extreme width is only acceptable if
there’s absolutely no “practical” way to better represent the “extreme width”.
without saying … what is “practical” represents a subject no Defendant or Lawyer
would want to have to define to a Jury in a Liability Court Case.
one Rearward Pointing Red, Clearance Light is required by FMVSS #108 on
each side of Trailers, RVs and Trucks that are over 80” in width.
allows Clearance Lights to be mounted from 12 inches to 10+ feet above the
pavement. However, when mounted more than
≈40” above the
pavement, Clearance Lights lose … some … most … or all … of their
safety effectiveness. Who cares? knowing how wide
a Trailer, RV or Truck is up high … beyond traffic eye level?
Common sense tells us that we should be warned of “Extreme Width” at close
to traffic eye level so we are made aware of what we must
“clear” in a closing fast, evasive scenario at night … or
in a torrential downpour, or blizzard, or under any other limited visibility
4. FMVSS #108
mandates that Clearance Lights must be clearly visible from 0° to 45°
“Outboard”*; however, be also aware that NHTSA used to mandate a
0° to 45° “Inboard”* visible scope as well, which they rescinded
several years ago for illogical and downright “stupid” reasoning**.
Here’s another regrettable example of the defiance of common sense
sanctioned by NHTSA and SAE.
*and within 10° Up to 10°
Down **See our additional Website writings on this issue
5. Also, be
aware that Clearance Lights … as well as all other Side and
Corner mounted Lights … are allowed by Federal Law to “stick
out” beyond the Standard 102 inch Trailer, RV and Truck width limit, as
are the Mirrors.
In real life
applications … if a typical Trailer, RV or Truck Multi Function
Tail Light Assembly is mounted to adequately represent the
“extreme width” … in effect … it actually seconds as an “extreme
width” Clearance Light. However, even under this circumstance, FMVSS
#108 still mandates that an extra
small bulb or LED Cluster must be used independent of the Multi
Function Light Tail Light Assembly while “also” representing the extreme width …
thus providing … in effect … a redundant Clearance Light.
adding a pair of superfluous Bulbs or LED Clusters on millions of
Trailers, RVs and Trucks … that are really not needed …
forces a more expensive and more energy-consuming situation onto the
American Public. Nevertheless, this is what the powers to be at NHTSA and
SAE have mandated, even if the Tail Light Assembly represents the “extreme
width”. Here’s still another example of NHTSA’s and SAE’s defiance of
In actual use in traffic, as long as an
“extreme width” mounted Tail Light keeps working, the width is properly
represented, and the fact there is no Back Up Clearance Light, represents an
“Inconsequential to Public Safety”* situation because the
“extreme width” would always be adequately represented
as mandated by FMVSS #108. *This is an
official “legal” allowance provided by FMVSS #108
6. When a
Trailer, RV or Truck … over 80” in width … uses Multi Function Tail Light
Assemblies that are “not” mounted to represent the “extreme width”
… then, “Independent” Clearance Lights must be
in order to satisfy the FMVSS #108 “extreme width” representing mandate.
In this kind of an independent Clearance Light scenario, the 8th
Function Clearance Bulb addition would not be required!
popular belief… Over 80” and Under 80” FMVSS #108
Classifications refer only to the
7-3/4in² “Effective Projected Luminous Lens Areas”* mandated by FMVSS
#108, whereas, over 80” and under 80” does “not” refer to Multi
Function Lights that have … or do not have … a separate 8th
Function Clearance Bulb. *
See our Website for further discussions on “EPLLA”
This “8th Function” versus
“EPLLA” misunderstanding is
widespread and must be clarified to all involved!
7. Again! …
mounting a Red, rear pointing “extreme width” indicating Clearance Light
completely independent of the Multi-Function Tail Light Assembly
is all that’s needed to save the … 8th Function … Bulb and Power
expense – only one pair – not two pair – are required.
that in addition to the rear pointing Red Clearance Lights, a pair
of front pointing Amber Clearance Lights are also
mandated to warn oncoming traffic of extreme width, meaning that
Four … 2 Red and 2 Amber … Clearance Lights are needed in all.
economical scenario to the using of Four independent Clearance Lights, is to
consider our dual-colored (Red/Amber) outboard
fender-mounted WingTips®, which saves the expense of two Front pointing
Amber Clearance Lights, not to mention providing more conspicuous,
and nearer to eye level, Side (pointing) Marker Lights
… plus giving the Driver a valuable,
rear view mirror seeable … and nearer to traffic eye level
… “Back Up, Location Indicator”
that all Big Rig drivers wouldn’t be without.
economical approach provides Trailer, RV and Truck Manufacturers (and ultimately
the vehicle owner/driver) saved dollars $ and provides bonus safety features
by using just two of our Wing Tips® that require the use of only a
single 1/3 Amp, easily found bulb, and an always serviceable “Rustproof” Bulb
Contact System. *Instead
of Four Independents
This not only
reduces the expense of Four Clearance Lights to Two, but it also
provides drivers with Safety plus Peace-of-Mind features none of our
total cost of using a pair of any of our 7 Function Light
Assemblies complimented with a pair of our Red/Amber, 5
Function Wing Tips® to the total cost of using any of our
Light Assemblies complimented with four separated conventional Clearance
Lights. You’ll find WingTips® save everyone involved money and complications!
ABOUT OPTICALLY COMBINED
As I pointed out earlier … FMVSS #108 does “not” allow a
Clearance Light to be “Optically Combined” with a Tail Light. This
means that both the Clearance and the Tail Light Functions must depend on
“separate” Illumination sources. However … contrary to popular beliefs
… both Functions are allowed to share common or overlapping
Lens Areas as long as both Functions are able to pass independent
Photometric FMVSS #108 mandated tests on their own with the other
Also be aware that FMVSS #108 “does allow” the
rear Side (pointing) Marker* light’s illumination source to be “Optically
Combined” ( shared) in order to also illuminate the Tail Light Test Pattern Scan
as long as both functions can independently and simultaneously pass
their corresponding FMVSS #108 Photometric Scan requirements. This means
both functions are allowed to use a single, illumination source while
also being allowed to share common and overlapping lens Areas.
*which I prefer to call a “Traffic and
Pedestrian Intersection Light”
Also, know that a rear or front pointing Clearance Light is
allowed to be “Optically Combined” with a rear or front Side (pointing) Marker
of this legal Clearance/Side Marker “Optical Combination” allowance
has saved knowledgeable Trailer, RV and Truck Manufacturers a
lot of dollars over the years because only a single Illumination
source and a contiguous lens for both the Clearance and Side
Marker Functions are permitted by FMVSS #108, thus eliminating the
$ expense $ of two lights as well as the corresponding $ installation, $ wiring
and $ power consumption costs.
see this Combination used on corners of full width Big Rigs, Trailers and RVs
that don’t use fenders, whereas a small light with a non shadowed*
FMVSS #108 180° Compliant output is mounted at a 45° Angle so that the 0°
to 45° Outboard Visual Path satisfies compliancy for the Clearance
Function while also projecting adequate Side (pointing) Lighting
to warn Intersection Traffic and nearby Pedestrians of the vehicle’s existence,
width and length.
*The bulb can’t be shadowed by the bulb
or LED holding system
In summary … be aware that
most of the knowledge and facts outlined, above, can be verified and studied in
more detail on our other Web writings under
SierraDesignMfg.com, or … by gambling a lot of your time and patience.
You can confirm my statements using NHTSA’s Website at
www.nhtsa.gov, which you’ll find
represents a confusing and lengthy challenge, but nevertheless, represents
Also, know that anyone
trying to tackle any confusing FMVSS #108 Subjects* is supposed to be
able to receive “timely” clarifying explanations using NHTSA’s “Legal
Interpretation System”, which (I’ve been told) must result in a NHTSA
“Legal Counsel” answer in no more than 6 weeks. Try out this Taxpayer paid-for
NHTSA service and … see what happens!
*And there are