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 SS-46A
  
  **Hardware Type:**
            Sign Supports, Mailboxes, and Delineator Posts
                          **Code:**
            SS-46A
                          **Date:**
            09/21/1995
                          **Testing Criteria:**
            NCHRP 350
                                  **Device Description:**
            Dual Unmodified Cedar Posts full dimension 4"x6"
                          **View PDF:**
            ss46a.pdf (83.58 KB)
    
    United States Department of Transportation - Federal Highway Administration

September 21, 1995

Refer to: HNG-14/SS-46A

Mr. Vincent F. Schimmoller
Regional Administrator (HRA-08)
Lakewood, Colorado

Dear Mr. Schimmoller:

This is in response to the South Dakota's Division Office memorandum dated September 7 requesting FHWA acceptance of the subject sign support that was crash tested for the State of South Dakota. You enclosed a copy of the report, dated July 1995, of the two crash tests conducted by the Federal Outdoor Impact Laboratory in McLean, Virginia.

The supports were dual post, 102-mm x 152-mm full dimension western red cedar with no weakening features, embedded 1220 mm into S-2 (weak) soil. The two posts were spaced 900 mm apart and both were struck with the test vehicle. The bottom of the 600-mm x 1500-mm, 3-mm thick aluminum sign panel was 2100 mm above the ground.

Full-scale crash testing was done in accordance with the National Highway Cooperative Research Program Report 350 Recommended Procedures for the Safety Performance Evaluation of Highway Features. Requirements for breakaway supports are found in the American Association of State Highway and Transportation Officials' (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. These specifications have been adopted by the FHWA. A summary of the crash test results is found below:

Test Number
			95F005
			95F006Vehicle Mass, kg
			839
			839Vehicle Impact Speed, m/s
			939 (35.6 km/h)
			26.9 (96.8 km/h)Vehicle Velocity Change, m/s
			3.1
			2.6Occupant Impact Speed, m/s
			2.3
			1.9Stub Height
			None
			NoneThese results meet the change-in-velocity and stub height requirements of the AASHTO and the FHWA. Because tests of wood posts in weak soils have been shown to be "worst-case" tests, further testing in strong soil is not deemed necessary. Therefore, the subject dual-post western red cedar sign supports are acceptable for use on the National Highway System, when selected by a highway agency. This acceptance does not cover the structural aspects of the sign support system. We assume that the State will develop wood grading and design specifications to ensure that in-service sign supports are comparable to those used in the crash tests.

Sincerely yours,

Jerry L. Poston, Chief
Federal-Aid and Design Division

Supplement to Geometric and Roadside Design Acceptance Letter No. SS-46

FHWA Safety Home| FHWA Home | Feedback

FHWA

United States Department of Transportation - Federal Highway Administration 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