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
                        Maintenance of Signs and Sign Supports


            
            In This Section
        Local and Rural Road Safety Program
                Training, Tools, Guidance and Countermeasures for Locals Practitioners
                Crash Facts
                
                APPENDIX B: CLEAR ZONE DESCRIPTION
The concept of clear zone is an approach to minimize the number and severity of crashes involving vehicles running off the road. Simply stated, it is a traversable area that starts at the edge of the traffic lane and extends laterally a sufficient distance to allow a driver to stop or return to the road before encountering a hazard or overturning. The traversable area would be considered safe, if there were no fixed objects, unless they are breakaway, and if the roadside geometry (either the fore slope, back slope, or ditch) was flat enough that a vehicle could safely traverse the area without tipping and rolling over. Roadside safety features include breakaway sign and light posts, and traversable drainage structures. Curbs are not considered a roadside safety feature since they can be easily mounted by errant vehicles; hence, their presence does not alter how clear zone is measured.

"Diagram. This diagram shows the parts of a clear zone. From left to right they are: back slope, drainage ditch, side slope, hinge point, shoulder, cross slope. The cross slope makes up the traveled way. The cross slope plus the shoulder makes up the roadway. The shoulder, hinge point, and side slope make up the clear zone. The Hinge point is defined as the point where the slope rate changes. The clear zone is defined as the area along the side of the traveled way including the shoulder that is available for recovery of an errant vehicle."

***Clear zone illustration***

A safe traversable slope can be either a recoverable slope or a non-recoverable slope with a clear run-out area at the bottom. A **recoverable slope** is a slope on which a motorist may, to a greater or lesser extent, retain or regain control of a vehicle and recover or stop. Slopes 1:4 (Vertical:Horizontal) or flatter are generally considered recoverable. A **non-recoverable, traversable slope**is a slope which is considered traversable but on which an errant vehicle will continue to the bottom. Embankment slopes from 1:3 and 1:4 may be considered traversable but non-recoverable if they are smooth and free of fixed objects. A clear run-out area is the flatter area at the toe of a non-recoverable slope available for safe use by an errant vehicle. Slopes steeper than 1:3 are not considered traversable and should not be found in the clear zone.

The objective of roadside safety is to provide and maintain as much clear zone as practical. The design clear zone is the minimum width to be provided on a project and is dependent upon speeds, the roadside geometry, and traffic volumes. Further details on clear zone can be found in the*Roadside Design Guide*.
      
  Book traversal links for APPENDIX B: CLEAR ZONE DESCRIPTION
      ‹ APPENDIX A: MATERIALS AND EQUIPMENT USED IN MAINTAINING SIGNS
                    Up
                    APPENDIX C: THREE TYPICAL WORK ZONE LAYOUTS FROM MUTCD ›
                
                Book:Maintenance of Signs and Sign Supports
              I: INTRODUCTION
                II. SIGN PRINCIPLES AND TYPES
                III. SIGN MATERIALS
                IV. SIGN SUPPORTS
                V. SIGN INSTALLATION
                VI. SIGN MANAGEMENT SYSTEM
                VII. INVENTORY
                VIII. INSPECTION
                IX. PREVENTIVE MAINTENANCE
                X. REPAIR AND REPLACEMENT
                XI. REPORTING AND RECORD KEEPING
                REFERENCES AND OTHER SOURCES OF INFORMATION
                APPENDIX A: MATERIALS AND EQUIPMENT USED IN MAINTAINING SIGNS
                APPENDIX B: CLEAR ZONE DESCRIPTION
                APPENDIX C: THREE TYPICAL WORK ZONE LAYOUTS FROM MUTCD 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