This article was published in the September 2015 edition of NTEA
News
Question: We are a truck equipment distributor
receiving numerous customer calls on rear underride requirements. There seems to
be some confusion as to when guards must be installed. Can you help
clarify?
Answer: Your customers’ uncertainty
is common. There are two similar requirements resulting in visually identical
features. They are intended to reduce injuries and fatalities associated with
lighter vehicles by preventing intrusion underneath the rear of a heavier
vehicle during an impact, as well as absorbing some of the collision’s energy.
One set of mandates applies to trucks, while the other is specific to trailers.
For straight trucks, longstanding rules for rear impact
protection (commonly known as an ICC bumper) are contained in 49 Code of Federal
Regulations (CFR) 393.86 (see Figure 1).
These directives, which are part of the Federal Motor
Carrier Safety Regulations (FMCSRs), apply to trucks meeting the definition of a
commercial motor vehicle (see definition from 49 CFR Part 390.5 below). The
Federal Motor Carrier Safety Administration (FMCSA) is the agency overseeing
these requirements. While not all trucks fall under their authority, most states
have adopted them for operations in intrastate commerce, so your customers and
the general public are best served by providing features to comply with these
same rear impact protection guidelines.
For “trailers and semitrailers with a gross vehicle
weight rating (GVWR) of 4,536 kg
or more”, rear impact guards are required
under Federal Motor Vehicle Safety Standard (FMVSS) 224, which is governed by
the National Highway Traffic Safety Administration (NHTSA) (see Figure
2).
After FMVSS 224 took effect in 1998, new trailers with a
GVWR of 10,000 pounds or more have had to comply with this standard (apart from
those meeting certain exclusions). However, trailers were previously subject to
the same requirements as straight trucks under the FMCSRs, so the timeline
dictating which set of mandates applies to a given vehicle can be confusing to
end users.
Another common misunderstanding involves similar
differences, such as guard positioning. For trucks, under the FMCSRs, the
structure used to meet the regulations must reside within 30 inches of the
ground and 2 feet of the rear extremity when the vehicle is unloaded. For
trailers under the FMVSSs, it must be no more than 22 inches above the ground
and within 1 foot of the rear extremity.
In addition, the structure used to meet FMVSS 224 can
look identical to the same horizontal beam with two vertical supports commonly
used to meet FMCSA rules on straight trucks. But the structure used for trailers
has performance requirements from FMVSS 223, whereas FMCSRs do not have test
regulations. This is often another source of uncertainty, where the
seemingly identical structure does not have the same, more stringent
directives when attached to a straight truck as when attached to a trailer —
even with the same GVWR.
Compounding the similar differences, performance
requirements for rear impact guards on trailers in Canada —
contained in Canadian Motor Vehicle Safety Standard (CMVSS) 223 — were
upgraded in 2007 to necessitate more energy absorption and
reduce intrusion. Although they may look identical, a guard on a U.S. trailer is
not accepted on the same trailer imported into Canada unless it meets the higher
performance criteria of CMVSS 223.
Efforts are being made to harmonize these requirements.
The U.S. and Canada are working to unify the respective rules of each country
across a number of industries — including automotive safety — and trailer rear
impact guards are on the list of standards to be made equivalent. Also, NHTSA
recently published an advance notice of proposed rulemaking in
an effort to synchronize truck and trailer rear underride protection in the U.S.
From 49 CFR Part
390.5
“Commercial motor vehicle means any
self-propelled or towed motor vehicle used on a highway in interstate commerce
to transport passengers or property when the vehicle—
- Has a gross vehicle weight
rating or gross combination weight rating, or gross vehicle weight or gross
combination weight, of 4,536 kg (10,001 pounds) or more, whichever is greater;
or
- Is designed or used to
transport more than 8 passengers (including the driver) for compensation; or
- Is designed or used to
transport more than 15 passengers, including the driver, and is not used to
transport passengers for compensation; or
- Is used in transporting
material found by the Secretary of Transportation to be hazardous under 49
U.S.C. 5103 and transported in a quantity requiring placarding under regulations
prescribed by the Secretary under 49 CFR, subtitle B, chapter I, subchapter
C.”
“Interstate commerce means trade, traffic, or
transportation in the United States—
- Between a place in a State and
a place outside of such State (including a place outside of the United
States);
- Between two places in a State
through another State or a place outside of the United States; or
- Between two places in a State
as part of trade, traffic, or transportation originating or terminating outside
the State or the United States.”
“Intrastate commerce means any trade, traffic, or
transportation in any State which is not described in the term ‘interstate
commerce.’”