USA Banner
  U.S. flag
              An official website of the United States government Here's how you knowOfficial US Government Icon
              **Official websites use .gov**A **.gov** website belongs to an official government organization in the United States.
            Secure Site Icon
              **Secure .gov websites use HTTPS**
                  A **lock** ( A locked padlock ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. 
 U.S. Department of Transportation Icon United States Department of Transportation
 Search DOT
            Search
                    About FHWAFHWA Organization
                Headquarters Offices
                Field Offices
                Strategic Plan
                Business Opportunities
                Staff Directories
                Careers
                Highway History
                Contact UsProgramsAcquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                Safety
                Browse by TopicsResourcesCore Highway Topics
                Federal Aid Essentials
                Automation
                Complete Streets
                Laws and Regulations
                Policy & Guidance Center
                Section 508
                Publications and Statistics
                Professional Development
                National Highway Institute
                Resource Center
                Accessibility Resource Library
                FHWA Research LibraryNewsroomPress Releases
                Speeches & Testimony
                Photos
                Videos
                Media ContactsMenu FHWA Highway Safety Programs Home
                        Safety
                        Roadway Departure Safety
                        Reduce Crash Severity
                        Hardware Eligibility Letters


            
            In This Section
        Roadway Departure Safety
                Strategic Approach
                                Strategic Plan
                Crash Emphasis Brochures
                Focused Approach
                Noteworthy Practices
                Partner Resources
                Keep Vehicles on the Road
                                Pavement Friction
                Horizontal Curve Safety
                Rumble Strips and Rumble Stripes
                Nighttime Visibility
                Provide for a Safe Recovery
                                SafetyEdge
                Clear Zones
                Reduce Crash Severity
                                Overview
                Hardware Eligibility Letters
                Focus on Reducing Rural Roadway Departures (FoRRRwD)
                                Overview
                All Public Roads
                Proven Countermeasures
                Systemic Approach
                Safety Action Plans
                FoRRRwD Resources
                
                Safety Eligibility Letter B-202
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-202
                          **Date:**
            04/16/2010
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            MWRSF
                          **Device Description:**
            Rough Stone Masonry Guardwall
                          **View PDF:**
            b202.pdf (59.07 KB)
    
    Safety Eligibility Letter B-202


						
			DOT logoU.S. Department of Transportation**Federal Highway Administration**
			1200 New Jersey Ave. S.E.Washington, D.C. 20590
            In Reply Refer to:  HSSD/B-202
			
			Dr. Ronald K. Faller
            	Research Assistant Professor
                527 Nebraska Hall
                P.O. Box 880529
                Lincoln, NE  68588-0529
            
            Dear  Dr. Faller:
            
            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: TL-2 Rough Stone Masonry Guardwall
            	Type of  system: Longitudinal Barriers-Aesthetic Barriers
                Test Level:  TL-2
                Testing  conducted by: Midwest Roadside Safety Facility
                Task Force  13 Designator: [FHWA will fill in this info]
                Date of  request: August 13, 2009
                Date of  completed package: January 13, 2010 
                Request  initially acknowledged: September 18, 2009
                
            You requested that we find this system acceptable for use on  the NHS under the provisions of the National Cooperative Highway Research  Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance  Evaluation of Highway Features.”
            **Requirements**Roadside safety devices should meet the guidelines contained  in the NCHRP Report 350 or the American Association  of State Highway and Transportation Officials’ Manual for Assessing Safety  Hardware (MASH). The FHWA  Memorandum “Identifying Acceptable Highway Safety Features” of July 25, 1997,  provides further guidance on crash testing requirements of longitudinal  barriers.
            **Description**The Rough Stone Masonry Guardwall system consists of three  main subsystems: (1) the reinforced concrete foundation slab; (2) the inner  reinforced concrete core wall; and (3) the rough masonry façade and attachment  system.
  
            The reinforced concrete foundation slab is 9 inches thick  and is laid on top of a 6-inch thick compacted crushed aggregate base. The top of the slab is positioned 6 inches  below the traveled way. In the slab both  bent and straight bars are used, as shown in Enclosure 1. A reinforced concrete core wall is constructed  on top of the foundation slab. The core  wall is rigidly attached to the slab using the vertical steel reinforcing bars  which extended out of the slab. Weep  holes are placed transversely through the parapet as shown in drawing  RSMG-1v15, sheet 14 of 15, of Enclosure 1.
            The 7 inch thick rough stone material is attached to the  inner core wall using: (1) a mortar bed on the front and top faces of the inner  core wall as well as a narrow region on the surface of the slab foundation; (2)  Dovetail Anchor Slots with Dovetail Anchor ties on the front surface of the  core wall; (3) Dovetail Anchor Ties wedged under the steel angles that are anchored  to the top surface of the core wall; (4) stainless steel, Z-clips attached to  the top surface of the core wall using masonry anchors; and (5) ASTM A36 steel  angles attached to the top surface of the core wall using Wedge-bolt Screw  Anchors with the upper angle leg extending into kerf cut into the bottom side  of the top capstone with the void space filled with mortar. The nominal top of the guardwall is 22 inches  from the traveled way. Enclosure 1  illustrates the design details and general layout of the rough stone masonry guardwall.
            The above description is associated with the single-face  rough stone masonry guardwall. Enclosure 2 shows design details and general  layout of double-face rough stone masonry guardwall. The double-face rough stone masonry guardwall  is structurally similar to the single-face guardwall (which was described above) but the  stones are attached to both sides of the core wall. This type of wall is used  where aesthetic appearance is deemed necessary for both sides of the wall (e.g.  median).
            **Crash Testing**The single-face 22 inch rough stone masonry guardwall was  crash tested by Midwest Roadside Safety Facility according to NCHRP 350 Test  2-11. The rough stone masonry guardwall was also crash tested according to Test  2-11where the test article was buried 2 inches deeper. In the latter test the top of the wall was 20  inches above the traveled way. Enclosure  3 shows the cross section of the end section detail view associated with the  second test article.
            **Findings**According to NCHRP 350, Test 2-10 and Test 2-11 are to be  conducted for longitudinal barriers for Test Level 2 approval. The 22 inch  rough stone masonry guardwall was crash tested according to Test 2-11 which  involves a 2000 kg pickup truck colliding with barrier at a speed of 70 km/h  and at an angle of 25 degrees. The test  article successfully passed the test and Enclosure 4 summarizes the results of  this test.
            The 20 inch rough stone masonry guardwall was also crash  tested according to Test 2-11 and the test article successfully passed the test  as can be seen in the summary sheet shown in Enclosure 5. However,  black contact marks and scratches on the vertical face of the guardwall found  in the post-crash investigation of the second test revealed that the guardwall  was overridden by the test vehicle. Consequently,  the rough stone masonry guardwall system is to be implemented with a nominal  top mounting height of 22 inch relative to the traveled way. This configuration allows for a  construction/operational height reduction tolerance of 2 inches.
            The second test shows that the rough stone masonry guardwall  system described in this letter cannot be used where the nominal height  of the parapet relative to the traveled way is less than 20 inches.
            Test 2-10 involves an 820 kg small passenger car impacting  the barrier at a speed of 70 km/h and at an angle of 25 degrees. Based on previous crash tests successfully  conducted on similar barriers with a small car, we concur with the University  of Nebraska Researchers that Test 2-10 is not critical and the completion of  the test is not necessary if the wall is constructed vertically according to  the enclosed design drawings.
            Regarding the texture of the rough stone masonry surface,  the masonry wall can have the maximum projections up to 38 mm beyond the neat  line, 50 mm deep raked joints, and beds 50 -75 mm thick. These  constraints are imposed according to Stone Masonry Guardwall-Design and  Construction Notes for Aesthetic Barriers dated May 15, 2002, (http://www.efl.fhwa.dot.gov/files/technology/abs/StoneMasonry/design-notes/stone_descon.pdf)  in order to prevent snagging of vehicles and/or excessive occupant compartment  intrusion.
            In your letter you also requested acceptance for the  double-face rough stone masonry guardwall. Your request is acceptable on the  grounds that a layer of rock attached to the other side of the core wall does  not degrade the performance of the system.
            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.
            Please note the following standard  provisions that apply to FHWA letters of acceptance:
            This acceptance is limited to the  crashworthiness characteristics of the systems.
            	Any changes that may adversely influence the  crashworthiness of the system 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 system being marketed is significantly different from the  version that was crash tested, we reserve the right to modify or revoke our  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, and that it will  meet the crashworthiness requirements of the FHWA and the NCHRP Report 350.
                To prevent misunderstanding by others, this letter  of acceptance is designated as number B-202 and shall not be reproduced  except in full. This letter and the test  documentation upon which it is based are public information. All such letters and this acceptance letter  shall not be construed as authorization or  consent by the FHWA to use, manufacture, or sell any patented system for which the applicant is not the  patent holder. The acceptance letter is  limited to the crashworthiness characteristics of the candidate system, and the  FHWA is neither prepared nor required to become involved in issues concerning  patent law. Patent issues, if any, are  to be resolved by the applicant.Sincerely yours,
						Signature of David A. Nicol
						David A. Nicol, P.E.
							Director, Office of Safety Design
							Office of Safety5 Enclosures U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

202-366-4000Subscribe to email updates
                    About
  

        
              About FHWA
                Careers
                Org Chart
                Staff Directories
                Work with UsPrograms
  

        
              Acquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                SafetyPolicies, Rights, Legal
  

        
              About DOT
                Accessibility
                Budget and Performance
                Civil Rights
                FOIA
                Information Quality
                No FEAR Act
                Office of Inspector General
                Privacy Policy
                USA.gov
                Web Policies and Notices
                Web StandardsNews & Events
  

        
              Newsroom
                Press Releases
                Speeches & Testimony
                Media Contacts
                Connect with Us