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                Safety Eligibility Letter B-110
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-110
                          **Date:**
            12/20/2002
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Caltrans Materials Engineering and Testing Services
                          **Device Description:**
            Texture Guidelines for SS and Vertical Concrete Barriers
                          **View PDF:**
            b110.pdf (938.68 KB)
    
    
December 20, 2002
HSA-10/B110
Mr. Rich Peter, Chief
  Roadside Safety Technology Branch
  Materials Engineering and Testing Services
  5900 Folsom Boulevard
  Sacramento, CA 95819-4612
Dear Mr. Peter:
In late September, you sent me one copy of a California Department of Transportation 
  test report dated September 2002 entitled “Crash Testing of Various Textured 
  Barriers” and one set of videotapes showing each of the tests you conducted.  
  Based on the results of these tests, you developed general guidelines for the 
  architectural treatment of single-slope barriers and requested formal acceptance 
  of these guidelines.
All of the textured designs were formed over and parallel to California's Type 
  60 concrete barrier, which has a constant slope approximately 9 degrees from 
  vertical.  Seven different textured designs were tested.  Four of these tests 
  met all appropriate Report 350 evaluation criteria at test level 3 and three 
  were considered unsuccessful.  A summary (and reference photograph) of each 
  tested design follows:
Deep Cobblestone design (Enclosure 1) – not acceptable, due to excessive 
    occupant compartment intrusion (2000P vehicle)
  Fluted Rib at 45 degrees (Enclosure 2) – not acceptable, due to rollover 
    (820C vehicle)
  Mission Arch (Enclosure 3) – acceptable performance when tested with 820C 
    vehicle.  2000P test waived
  Deep Cobblestone Reveal (Enclosure 4) – acceptable performance with 2000P 
    vehicle.  820C test waived
  Drystack (Enclosure 5) – acceptable performance with 2000P vehicle.  820C 
    test waived
  Fractured Granite (Enclosure 6) – acceptable performance with 2000P vehicle.  
    820C test waived
  Shallow Cobblestone (Enclosure 7) – deemed not acceptable due to 2000P vehicle 
    driveshaft separation in crash.  Report 350 evaluation criteria were met, 
    howeverBased on analysis of all test results, you proposed the following general texture 
  guidelines for use on single-slope concrete barriers in California:
Sandblast textures with a maximum relief of 9.5 mm.
  Images or geometric patterns inset into the face of the barrier 25 mm or 
    less and having 45-degree or flatter chamfered or beveled edges to minimize 
    vehicular sheet metal or wheel snagging.
  Textures or patterns of any shape and length inset into the face of the 
    barrier up the 13-mm deep and 25-mm in width.
  Any pattern or texture with gradual undulations that have a maximum relief 
    of 20 mm over a distance of 300 mm.
  Gaps, slots, grooves or joints of any depth with a maximum width of 20 
    mm and a maximum surface differential across these features of 5 mm or less.
  Any pattern or texture with a maximum relief of 64 mm, if such pattern 
    begins 610 mm or higher above the base of the barrier and all leading edges 
    are rounded or sloped to minimize any vehicle snagging potential.  No part 
    of this pattern or texture should protrude above the plane of the lower, untextured 
    portion of the barrier.Based on my staff's review of the information you submitted, I agree that the 
  above guidelines for concrete barrier texturing are acceptable and will not 
  adversely affect the NCHRP Report 350 test level of the barrier to which a texture 
  or pattern is applied.  I also agree that any texture or pattern meeting these 
  guidelines can be applied to all crashworthy single slope or vertical wall designs.  
  It is clear from the crash test results that textured barriers can result in 
  more vehicular body damage in a crash due to increased friction even if their 
  crash performance remains within acceptable limits. Although the barriers you 
  tested were 1220-mm and 1422-mm tall, review of the crash and post-crash vehicle 
  trajectories indicate that these guidelines may also be applied to vertical 
  walls as low as 685 mm and to any single-sloped barrier at the standard 813-mm 
  height or higher.  These treatments may prove acceptable on New Jersey and F-shape 
  concrete barriers if the treatment is applied only to the upper sloped face 
  of the barriers, but some crash testing would be advisable to verify good performance 
  with these shapes.  I understand that anyone wishing detailed design drawings 
  for any of the tested patterns may contact you by telephone at (916) 227-7257 
  or via e-mail at rich_peter@dot.ca.gov.
Finally, I wish to commend you on this very timely research.  Today, more state 
  and municipal transportation agencies are seeking aesthetic traffic barriers 
  that are also crashworthy for use in historic and environmentally sensitive 
  areas.  The above guidelines provide a means for satisfying both goals without 
  additional crash testing and increased project delays and costs.
Sincerely yours,
Harry W. Taylor
Acting Director, Office of safety Design
7 Enclosures U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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