Mr. Steve L. Brown 

 President 

 Trinity Highway Safety Products Division 

 P.O. Box 568887 

 Dallas, Texas 75356-8887 

Dear Mr. Brown: 

In his September 19, 2005, letter to Mr. Richard Powers, Mr. Don Johnson requested the 

Federal Highway Administration (FHWA) acceptance of a new strong post W-beam guardrail 

design called the T-31. With the letter, he also sent copies of a Texas Transportation Institute 

(TTI) report dated September 2005, entitled “NCHRP Report 350 TL-3 Testing of the T-31 

W-beam Guardrail”, and videotapes of the two tests that were conducted. Both of these tests 

were run using the new test vehicles that are being proposed as replacements for the 820C and 

2000P vehicles in the ongoing National Cooperative Highway Research Program (NCHRP) 

project to update to Report 350. Specifically, test 3-10 was conducted using a car weighing 

approximately 1100 kg impacting the barrier at a 25-degree angle and test 3-11 was conducted 

with a quad-cab pickup truck with a nominal weight of 2270 kg. 

The T-31 guardrail uses standard 12-gauge W-beam panels mounted on modified W6 x 

8.5 steel posts with a top-of-rail height of 31 inches. The modified posts, called SYLP 

(Steel Yielding Line Posts) posts are 6-feet long and set in the ground to a depth of 40 inches. 

Each post has four 13/16-inch diameter holes in the flanges at the ground line. The rail is 

attached to each post without an offset block using a 5/8-inch diameter x 1-3/4-inch long 

special bolt with a slotted countersunk head. A 6-inch long section of W-beam called a flange 

protector (backup plate) is used at each post. All splices in the W-beam rail elements fall 

midspan, between adjacent posts. Design details for the SYLP post and its unique connection 

bolt are shown on Enclosure 1. 

As noted above, the T-31 was first tested using the heavier vehicles (and the increased impact 

angle for the small car) that are proposed for use in the Report 350 update that is currently 

nearing completion. However, after reviewing the results of the two tests you ran under the 

400 Seventh St., S.W. 

Washington, D.C. 20590

In Reply Refer To: HSA-10/B-140 

November 3, 2005 
2

proposed guidelines and realizing that it will be several years before any new guidelines 

become effective, my staff concluded that the current small car test could be more critical than 

the anticipated future test 3-10. Specifically, it was thought that a lighter small car impacting 

at the standard 20-degree angle would have contact with more of the T-31 support posts than 

occurred in your test with the heavier car at the 25-degree impact angle. Consequently, on 

October 19, 2005, the TTI conducted the standard car test and sent the summary results to 

Mr. Powers on October 26, 2005. Although the occupant impact velocities and ridedown 

accelerations were somewhat higher in the second test, all values remained under the NCHRP 

Report 350 preferred limits. There was less rail deflection with the shallower impact angle but 

more damage to the vehicle itself. Summary sheets for each of the three tests are shown as 

Enclosure 2. 

Based on these test results, the T-31 barrier system as described above is classified as a test 

level 3 barrier and may be used on the National Highway System when such use is acceptable 

to the contracting authority. The T-31 guardrail may be considered crashworthy under both the 

existing Report 350 guidelines and under the new guidelines when they are formally adopted, 

assuming that the test matrix currently being proposed by the researchers remains unchanged. 

Please note the following standard provisions that apply to the FHWA letters of acceptance:

• Any changes that may adversely influence the crashworthiness of this barrier will require 

a new acceptance letter.

• Should the FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the device being marketed is 

significantly different from the version that was crash tested, it reserves the right to 

modify or revoke its acceptance.

• You will be expected to supply potential users with sufficient information on design and 

installation requirements to ensure proper performance.

• You will be expected to certify to potential users that the hardware furnished has 

essentially the same chemistry, mechanical properties, and geometry as that submitted for 

acceptance. 

• To prevent misunderstanding by others, this correspondence, designated as acceptance 

letter B-140, shall not be reproduced except in full. This letter, and the test 

documentation upon which this letter is based, is public information. All such letters and 

documentation may be reviewed at our office upon request. 

• Since the T-31 guardrail is a steel product, the provisions of Title 23, Code of Federal 

Regulations, Section 635.410 apply to its use on federally funded projects.

• The T-31 guardrail includes patented components and is considered a proprietary 

product. When proprietary devices are specified by a highway agency for use on 

federally-funded projects they: (a) must be supplied through competitive bidding with 

equally suitable unpatented items; (b) the highway agency must certify that they are 

essential for synchronization with existing highway facilities or that no equally suitable 

alternative exists or; (c) they must be used for research or for a distinctive type of 

construction on relatively short sections of road for experimental purposes. Our 

regulations concerning proprietary products are contained in Title 23, Code of Federal 

Regulations, Section 635.411.
3

• This acceptance letter shall not be construed as authorization or consent by the FHWA to 

use, manufacture, or sell any patented device for which the applicant is not the patent 

holder. Patent issues, if any, are to be resolved by the applicant. 

Sincerely yours, 

 

/original signed by John R. Baxter/ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

2 Enclosures 
Figure 7. Details of the SYLP for the T-31. 

10 

21 

0.000 s 0.080 s 0.220 s 

General Information Test Agency............................... Test No. .................................... Date ...........................................Test Article Type........................................... Name .........................................

Installation Length (m)...............

Material or Key Elements ..........

Soil Type and Condition.............Test Vehicle Type........................................... Designation................................ Model......................................... Mass (kg) Curb........................................ Test Inertial............................. Dummy ................................... Gross Static............................

Texas Transportation Institute 220570-4 10-19-2005 Guardrail T-31 68.6 W-Beam Guardrail on Steel Yielding Line Posts with Splices at Mid-Span Standard Soil, Dry Production 820C 1997 Geo Metro805 825  75 900 

Impact Conditions  Speed (km/h) ............................. Angle (deg) ................................Exit Conditions Speed (km/h) ............................. Angle (deg) ................................Occupant Risk Values

Impact Velocity (m/s) 

 Longitudinal ............................ Lateral .................................... THIV (km/h) ...............................

Ridedown Accelerations (g’s) 

 Longitudinal ............................ Lateral .................................... PHD (g’s) ................................... ASI ............................................Max. 0.050-s Average (g’s)  Longitudinal ............................ Lateral .................................... Vertical ...................................

102.1  20.3 58.0 -11.4  6.4  5.8 29.8 -12.9  7.6  14.8  1.05 -10.2  6.8  2.4 

Test Article Deflections  Dynamic ..................... Permanent.................. Working Width............Vehicle Damage Exterior  VDS......................... CDC ........................ Max. Exterior 

 Vehicle Crush (mm

 Interior  OCDI ....................... Max. Occupant Com

 Deformation (mm)

Post-Impact Behavior

(during 1.0 sec after im

 Max. Yaw Angle (de

Max. Pitch Angle (deMax. Roll Angle (deg

Figure 15. Summary of results for NCHRP Report 350 test 3-10 on T-31 W-beam guardrai
33 

0.000 s 0.206 s 0.413 s 

General Information Test Agency...............................  Test No. ....................................  Date ........................................... Test Article Type...........................................  Name .........................................  Installation Length (m) ...............  Material or Key Elements .......... Soil Type and Condition............. Test Vehicle Type...........................................  Designation................................  Model.........................................  Mass (kg)  Curb........................................  Test Inertial.............................  Dummy...................................  Gross Static............................ 

Texas Transportation Institute 220570-2 08-02-2005 Guardrail T-31 68.58 W-Beam Guardrail on Steel Yielding Line Posts with Splices at Mid-Span Standard Soil, Dry Production 2270P 2002 Dodge Ram 1500 2207 2299 No dummy 2299 

Impact Conditions  Speed (km/h) .............................  Angle (deg) ................................ Exit Conditions Speed (km/h) .............................  Angle (deg) ................................ Occupant Risk Values Impact Velocity (m/s)  Longitudinal ............................  Lateral ....................................  THIV (km/h) ...............................  Ridedown Accelerations (g’s)  Longitudinal ............................  Lateral ....................................  PHD (g’s) ...................................  ASI ............................................ Max. 0.050-s Average (g’s)  Longitudinal ............................  Lateral ....................................  Vertical ................................... 

97.6 26.8 63.8 14.8  5.0  5.1 23.9 -6.1  7.4  7.5 0.70 -5.0  5.5  1.8 

Test Article Deflections 

 Dynamic ..................... Permanent.................. Working Width............Vehicle Damage Exterior  VDS......................... CDC ........................ Max. Exterior  Vehicle Crush (mm Interior  OCDI ....................... Max. Occupant Com Deformation (mm) Post-Impact Behavior (during 1.0 sec after im Max. Yaw Angle (de Max. Pitch Angle (de Max. Roll Angle (deg

Figure 22. Summary of results for NCHRP Report 350 test 3-11 on the T-31. 
0.000 s 0.080 s 0.220 s 

General Information Test Agency...............................  Test No. ....................................  Date ........................................... Test Article Type...........................................  Name .........................................  Installation Length (m) ...............  Material or Key Elements .......... Soil Type and Condition............. Test Vehicle Type...........................................  Designation................................  Model.........................................  Mass (kg)  Curb........................................  Test Inertial.............................  Dummy...................................  Gross Static............................ 

Texas Transportation Institute 220570-4 10-19-2005 Guardrail T-31 68.6 W-Beam Guardrail on Steel Yielding Line Posts with Splices at Mid-Span Standard Soil, Dry Production 820C 1997 Geo Metro 805 825  75 900 

Impact Conditions  Speed (km/h) .............................  Angle (deg) ................................ Exit Conditions Speed (km/h) .............................  Angle (deg) ................................ Occupant Risk Values Impact Velocity (m/s)  Longitudinal ............................  Lateral ....................................  THIV (km/h) ...............................  Ridedown Accelerations (g’s)  Longitudinal ............................  Lateral ....................................  PHD (g’s) ...................................  ASI ............................................ Max. 0.050-s Average (g’s)  Longitudinal ............................  Lateral ....................................  Vertical ................................... 

102.1  20.3 51.8 -11.4  6.4  5.8 29.8 -12.9  7.6  14.8  1.05 -10.2  6.8  2.4 

Test Article Deflections  Dynamic ..................... Permanent.................. Working Width............Vehicle Damage

 Exterior  VDS......................... CDC ........................ Max. Exterior  Vehicle Crush (mm Interior  OCDI ....................... Max. Occupant Com Deformation (mm) Post-Impact Behavior (during 1.0 sec after im Max. Yaw Angle (de Max. Pitch Angle (de Max. Roll Angle (deg

Summary of results for NCHRP Report 350 test 3-10 on the T-31 Guardrail.