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, however 

Based on analysis of all test results, you proposed the following general texture 

guidelines for use on single-slope concrete barriers in California: 

1. Sandblast textures with a maximum relief of 9.5 mm. 
2. 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. 

3. 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. 

4. Any pattern or texture with gradual undulations that have a maximum relief 

of 20 mm over a distance of 300 mm. 

5. 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. 

6. 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 singlesloped 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 
Deep Cobblestone Design - not acceptable 
Fluted Rib at 45 degree Design - not acceptable 
Mission Arch Design 
Deep Cobblestone Reveal Design 
Drystack Design 
Fractured Granite Design 
Shallow Cobblestone Design – not acceptable