U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
December 23, 2008
In Reply Refer To: HSSD/B-88F
Mr. Jesper Sorensen
1557 NW. Ballard Way
Seattle, WA 98107
Dear Mr. Sorensen:
This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of a roadside safety system for use on the National Highway System (NHS).
|Name of system:||SAFENCE in 1:4 Sloped Medians|
|Type of system:||Cable Barrier|
|Test Level:||MASH TL-3|
|Testing conducted by:||Swedish Road and Transport Research Institute (VTI)|
|Date of request:||October 21, 2008|
|Date of completed package:||Video link received November 18, 2008|
|Drawings received December 10, 2008|
You requested that we find this system acceptable for use on the NHS under the provisions of the proposed American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware 2008 (MASH-08).
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350. The FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers. You have chosen to anticipate the adoption of MASH-08, an option that the FHWA has offered with the understanding that additional testing may need to be done if changes to the test criteria are made before MASH-08 is formally adopted.
The Blue System/Safence has been tested and accepted under the following the FHWA Acceptance Letters:
|B-88||July 13, 2001||TL-3||4||Roadside Driven elliptical posts|
|B-88A||January 28, 2004||TL-3||4||3504RI Median Driven I posts|
|B-88B||June 08, 2004||TL-3||4||Concrete footers|
|B-88C||May 26, 2005||TL-3||4||Roadside Allow "C" posts|
|B-88D||December 27, 2006||TL-4||3||3RC Modified “C” posts|
|B-88E||July 31, 2007||TL-4||4||Add fourth Cable to TL-4 Safence|
Cable heights in millimeters in these systems are as follows:
|B-88||July 13, 2001||TL-3||480||630||780||930|
|B-88A||January 28, 2004||TL-3||480||560||640||720|
|B-88B||June 8, 2004||TL-3||480||560||640||720|
|B-88C||May 26, 2005||TL-3||480||630||780||930|
|B-88D||December 27, 2006||TL-4||480||640||720||-|
|B-88E||July 31, 2007||TL-4||480||560||640||720|
|B-88F||(This Letter) MASH||TL-3||500||785||(880*)||975|
* (Tested with 3 cables – 4 cable optional)
Your current request is for the three-cable Safence to be found acceptable when placed in a 1:4 – 1:4 sloped ditch. As the installation in a sloped median is not covered in MASH-08, Mr. Jan Wenäll of VTI discussed the proposed test requirements with Mr. Nicholas Artimovich of my office. The 19mm (3/4 in) diameter cables were installed at heights of 500 mm, 785 mm, and 975 mm (19.7 in, 30.9 in, 38.4 in) above the ground using the Safence “C” shaped posts, spaced 4.9 m (16 ft) apart, each with a slot in the top. The posts were rolled from ASTM A1011-04a high strength – low alloy grade 50 steel. They were 2100 mm (82.7 in) long with 1050 mm (41.3 in) above the ground and an embedment depth of 1050 mm (41.3 in) in “standard soil.”
The test barrier was located 1200 mm (4 ft) down from the slope break point. The three
“Trulay Ø 19mm” steel cables were tensioned to 11.77 kN (2645.55 lbf) corresponding to the tension requirement for ambient temperatures of 37.8 degrees C or 100.0 degrees F. Details of the posts and cable arrangement are shown in the enclosed drawings for reference.
The median ditch constructed at VTI was 8 m (26 ft) wide and 55 m (181 ft) long. The median slopes were 1:4 and the rounded invert of the ditch was approximately 1m (3.3 ft) below the adjacent terrain. The test article length was 185 m (607 ft) between concrete anchors (as the installed length of the barrier was longer than the actual median ditch, part of the barrier was installed on level ground beyond the end of the ditch).
Two tests were conducted on the Blue System/Safence in the 1:4-1:4 median. In test 3-11 the Ford Transit 350E (2222 kg, 4898 lb) impacted at 101.5 km/hr (63 mph) at 25 degrees. The vehicle was redirected by the barrier and stopped after traveling about 55 m (180 ft). In test 3-10 the Kia Rio (1124 kg, 2478 lb) with a dummy impacted at a speed of 103 km/hr (64 mph) at an angle of 25 degrees. In Test 3-10 the vehicle traversed the ditch and impacted the backslope prior to contacting the barrier. The vehicle was restrained by the barrier and stopped after traveling about 41 m (134 ft). The maximum dynamic deflection of the barrier was 5 m (16.4 ft). Summary pages of the tests are enclosed for reference.
The vehicle trajectories and occupant risk values were within the evaluation criteria of MASH-08. Therefore, the system described above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.
You also asked for three additional considerations:
1) The tests were performed with two different anchors in order to evaluate both types. One was
a trapezoidal precast anchor and the other was square and was poured in the field. As no movement of either anchor was observed, both will be acceptable.
2) The tests were performed with the 3-cable Safence. You requested that the 4-cable version
also be considered acceptable under similar median conditions. The 4th cable will be placed between the middle and top cables at a height of 880 mm (34.6 in). We concur in this addition with the provision that the fourth cable have its own slot in the end anchor.
3) Safence posts may be installed with pre-cast footings, or concrete footings that are cast in
place. You asked that the use of either steel sleeves or plastic sleeves be acceptable for forming the post hole in the concrete. As the posts remain in the sleeves during impact, there is no difference in performance between steel or plastic sleeves. Therefore either type sleeve is acceptable in any Safence installation using cast-in-place footings.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
• This acceptance is limited to the crashworthiness characteristics of the systems and does not cover their structural features, nor conformity with the Manual on Uniform Traffic Control Devices.