TESTING FAQs

 
What was tested?
These tests were conducted in accordance with NCHRP Report 350 at Southwest Research Institute (SwRI), an accredited and independent research facility. Report 350 sets forth the performance evaluation criteria applicable to the ET Plus® System and many other roadside safety features used on U.S. highways. 

The ET Plus® extruder heads tested in all eight tests were randomly selected by the FHWA from inventory at the California Department of Transportation.  These extruder heads complied with all design tolerances and are representative of what is in use on U.S. highways.
Why were there two different heights?
The FHWA requested the two different heights (27-3/4” and 31”) be tested because these are the two most standard heights for guardrail installation. The 27-3/4" height is the most commonly used height and satisfies the guardrail test height the Virginia Department of Transportation requested of Trinity. The 31" height is the height of the guardrail involved when the ET Plus® was successfully crash tested in 2005.

 

What vehicles were used?

Trinity Highway used vehicles that comply with NCHRP Report 350 test criteria. These vehicles were approved by the FHWA prior to initiating the tests.


Where were the tests conducted?

All eight of the tests were conducted at the Southwest Research Institute (SwRI) in San Antonio, Texas. SwRI is one of the crash test laboratories named on FHWA’s list of laboratories suitable for performing NCHRP Report 350 crash tests. SwRI is an independent testing facility approved by the FHWA.

Was the Southwest Research Institute involved in any previous testing of the ET Plus® System and does it have a financial interest in the ET Plus® System with 4-inch guide channels installed on the extruder head?

No. SwRI has not performed previous testing on this product and does not have a financial interest in this product.

Why only four tests per height, isn't the full range of NCHRP Report 350 tests broader?

These are the tests requested by the FHWA. The other tests in the Test Level 3 matrixes are for the longitudinal integrity of the guardrail downstream of the end terminal head. 

When did the tests begin?

The 27 ¾-inch guardrail height tests began in early December 2014, and were concluded on January 6, 2015. The 31-inch guardrail height tests began on January 15, 2015 and were concluded on January 27, 2015. 


Who was allowed to observe the tests at SwRI?

FHWA engineers, American Association of State Highway and Transportation Officials (AASHTO) representatives, interested state DOT representatives and media representatives from a media selected “pool” were present at the testing. 


What is gating?

A gating end terminal allows an errant vehicle to pass through the system at certain impact angles along a portion of the end terminal system’s length, slowing the vehicle as it enters the area behind the end terminal installation. 


What is extruding?

An end terminal is developed to prevent an errant vehicle from impacting the blunt end, or turned down end of roadside guardrail installations. Upon impacting an extruding end terminal system, the extruder head component of that system is designed to be pushed down a length of W-beam guardrail installed behind the extruder head by the force of the impacting vehicle, while flattening the guardrail as it passes through the converging plates inside the extruder head and then exits the extruder head, diverting the flattened guardrail to the side and away from the vehicle.  This process dissipates the kinetic energy of a vehicle impacting the end terminal’s extruder head. The end terminal system consists of the impact/extruder head component containing the converging plates with an inlet in which the guardrail is pre-positioned in order to initiate the extruding process upon impact of the vehicle with the end terminal head.  

Does the FHWA regulate roadside safety hardware like guardrails and their components?

No. FHWA does not regulate or prescribe requirements for highway hardware. States and territories select, install and maintain their roadside hardware.

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept
Does FHWA establish crash test criteria for roadside safety hardware?

No. The American Association of State Highway and Transportation Officials (“AASHTO”), in conjunction with the Transportation Research Board, develops crash test criteria and performance standards. FHWA provides technical input to AASHTO standards but has no vote when a decision is made by AASHTO for establishing testing criteria and performance standards.

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept

What is FHWA's role in the review of roadside safety hardware?

FHWA does not regulate roadside highway hardware, nor does FHWA endorse any product. FHWA (a) provides a service to state DOTs by reviewing crash test results of roadside safety hardware conducted by accredited testing facilities certified to perform crash testing, (b) determines whether or not the test results demonstrate that a device meets applicable crash test criteria; and (c) issues an eligibility letter stating a device is eligible for Federal-aid reimbursement if it meets the applicable crash test criteria. FHWA provides its crash test review, verification and eligibility service to reduce the burden upon the states that lack the technical expertise or staff resources to determine whether a particular safety device meets the relevant roadside safety hardware criteria. All eligibility letters are posted on FHWA's Office of Safety website. Importantly, a letter of funding eligibility is not required for federal funding – a state may opt to certify a product's crashworthiness on its own. The letters accepting a highway product for use on a federal-aid highway were, until very recently, called “acceptance letters”. 

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept

What is the role of the states?

States own and operate the National Highway System (NHS), make the day-to-day decisions on the use of federal funding within the statutory requirements prescribed by Congress and oversee the design, construction, maintenance, and operation of the NHS in compliance with federal and state regulations. States decide which safety hardware to install on their roads and are responsible for such installations as well as on-going maintenance, repair and replacement of such hardware. The states also set performance criteria for roadside safety hardware as members of AASHTO.

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept


Are FHWA eligibility letters a regulatory requirement for guardrails, guardrail end terminals and other types of roadside safety hardware to be installed in states?

No. An FHWA eligibility letter is not required for states to use roadside safety hardware and receive federal aid. States may make their own determinations, relying on certifications from accredited crash test facilities or crash test data from a manufacturer. A state DOT may also place limits on the use of a device, require additional testing or an in-service evaluation. However, it is FHWA policy that any roadside safety hardware placed on the NHS meets the applicable crash test criteria in order for the state to receive federal reimbursement for that hardware. 

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept

Why did the FHWA request Trinity test the ET Plus® System to the specifications under NCHRP Report 350? Why did FHWA not ask Trinity to test to the current MASH criteria implemented in 2011?

All roadside safety hardware receiving an eligibility letter before 2011 must meet the appropriate crash test criteria that existed at the time the eligibility letter was originally received. In the case of the ET Plus® System this is NCHRP Report 350. The ET Plus®System being tested received an FHWA acceptance letter first in 2000. The system that was crash tested in May 2005, that utilized 4-inch guide channels attached to the extruder head, first received an acceptance letter in 2005 (FHWA eligibility letters were called acceptance letters in 2005). Roadside safety hardware developed after 2011 is required to be tested using the MASH criteria. 

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept


 

Why is the Trinity ET Plus® System still eligible for funding when there are questions about the product's safety?

FHWA must rely on and take appropriate action based on credible data and information provided by the states, AASHTO and other stakeholders. FHWA has made clear that there is no conclusive evidence at this time that indicates this product is not performing in the field as designed. When queried in 2012 and 2014, the states did not provide information claiming otherwise.

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept
 



How does FHWA help states reduce the number of crashes that result from roadway departures and guardrail collisions?

A roadway departure crash is defined as a non-intersection crash which occurs after a vehicle crosses an edge line or a center line, or otherwise leaves the traveled way. FHWA's Roadway Departure Safety Program provides technical assistance, tools and information for transportation practitioners, decision makers, and others to assist them in preventing and reducing the severity of roadway departure crashes, at http://safety.fhwa.dot.gov/roadway_dept/ 

FHWA provides training to states regarding the proper design, installation, and maintenance of roadside safety hardware. Information on roadside safety hardware that has been tested for crashworthiness according to recommended procedures can be found at 
http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/ 

(Sourced from the FHWA FAQ, November 12, 2014 http://safety.fhwa.dot.gov/roadway_dept
What are the factors that impact or affect the performance of the guardrail end terminal systems that are tested pursuant to NCHRP Report 350?

There are many factors that can affect the performance of a guardrail end terminal system and its components when it is struck by an errant vehicle such as, to name a few, (a) the proper selection of the device for the installation site, (b) correct assembly and installation, (c) routine and timely maintenance, repair and replacement of the device, (d) road and weather conditions, (e) traffic volume, (f) the speed of the vehicle striking the end terminal and whether it is towing any form of trailer, (g) the type and size of the vehicle that hits the end terminal, (h) the angle of impact and (i) the soil conditions around the installation can all affect how the device performs. The wide range of factors is why it is important to know details about the accident before determining whether or not highway hardware did or did not perform as crash tested. 

 

                 


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RELATED LINKS

ACCEPTANCE LETTERS