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 EdgeSM Design and Construction Guide


            
            In This Section
        SafetyEdge
                General Information
                Safety
                Pavement and Maintenance
                Design and Construction
                Policies and Practices
                Multimedia
                Demonstrations
                FAQs
                
                SECTION 4: SPECIFIC CONSIDERATIONS FOR CONSTRUCTING THE Safety EdgeSM IN CONJUNCTION WITH NEW CONCRETE PAVEMENTS OR CONCRETE OVERLAYS
This section identifies issues that need to be monitored during the construction of PCC pavements. All of the PCC demonstration projects that were used for preparing this Guide included the use of slip-form paving to form the Safety EdgeSM. A benefit of forming the Safety EdgeSM during PCC slip-form paving is the sensitivity to edge slump is reduced.

4.1 Design Features and Shape

The Safety EdgeSM is designed to create a 30 degree finished angle relative to the pavement cross slope as shown in Figure 14 and should be constructed on a similar structural base as the adjoining monolithically placed lane/shoulder. During design, the structural base width needs to account for the Safety EdgeSM width.
Figure 14. Recommended Safety EdgeSM configuration for PCC pavements and overlays.**Figure 14. Recommended Safety EdgeSM configuration for PCC pavements and overlays.**** Note, Recommended Rise to Run ratio range 1:1.2 to 1:2.0. The range of slope is equal to 26° to 40°.*

4.2 Equipment – PCC Safety EdgeSM Devices

This part describes the modifications that must be made to a slip form concrete paver to form a Safety EdgeSM. It also notes the essential attributes of a concrete paver that are necessary to create an effective Safety EdgeSM. When a slip form paver is not being used, the Safety EdgeSM needs to be manufactured or created as part of the forms – one side of the forms will have an angle of 30 degrees rather than being vertical.

Currently, there are no commercially available Safety EdgeSM devices for PCC pavers or forms. Custom devices, however, can be fabricated by modifying the finishing pan of the paver (refer to Figure 15). The pan is essentially configured to form an inverted curb under the pan close to the end gate. The steel components of the assembly need to be robust in order to resist bending during paving operations from the force of the plastic PCC. The following provides a description of the modifications that were made to a Gomaco paver that was used on one of the PCC demonstration projects and identifies some of the issues or items that should be considered in fabricating the Safety EdgeSM profile.

A template was created for the Safety EdgeSM profile to ensure correct dimensions. The template was used to manufacture a stainless steel profile pan of the desired shape and dimensions. Portions of the existing profile pan were removed to fit in the new Safety EdgeSM profile.**[Note: The contractor decided against welding the Safety Edge****SM********profile to the bottom of the existing profile section or pan because of a concern that the welds might tear the finished PCC.]**
	A 2-inch finish tail on the stainless steel Safety EdgeSM profile was fabricated to help finish the portion of the edge where it goes from slope to vertical. When going through existing intersections, driveways, or where the grade is not exact on the outside edge, the 2-inch finish tail did drag in some locations. For the demonstration project, the contractor cut one inch off of this tail and it performed well, but cutting 0.5 inches from the tail would have also worked well.
	Adjusting bolts were fitted to the Safety EdgeSM profile pan. One adjustment bolt was on the sloped section in case an adjustment had to be made if the edge profile was not finishing properly.
	In setting up the paver, care was taken to position the vibrators in the specific locations for proper consolidation of the Safety EdgeSMâ€“near the breakpoint.Unlike the Safety EdgeSM attachments for AC layers or overlays, the modifications made to the concrete paver cannot be easily removed and replaced. The modifications can be removed, but the parts must be cut from the pan using a torch or grinder. Touchup of the pan is required to return the unit to service on standard PCC pavements.

4.3 Concrete Mixtures

Demonstration projects completed to date have used standard concrete mixes. No changes to the mix were needed to accommodate the SE.

4.4 Safety EdgeSM Construction

This part of the Guide discusses items of interest to PCC paving projects when a Safety EdgeSM is to be placed as part of the new construction or rehabilitation project.

*PCC Placement*

Normal paving procedures are usually sufficient for forming the Safety EdgeSM on mainline sections of the roadway using slip form paving operations and equipment. Material properties of the hardened concrete from the edge and the interior of the pavement have been demonstrated to be similar.
Figure 15. View of the Safety EdgeSM device from front of paver.**Figure 15. View of the Safety EdgeSM device from front of paver.***Transitioning Between Different Edge Profiles*

It is recommended to have a transition from a no Safety EdgeSM section to a Safety EdgeSM section to avoid a vertical edge perpendicular to traffic (i.e. similar to beginning section of bridge concrete rail/parapet where the bottom of the rail/parapet is modified to reduce the probability of vehicle tire snagging).

An important issue to be addressed is the intersection of cross roads where a vertical edge is required. Due to the fixed nature of the edge and shoe assembly, the contractor can consider different options depending on the number and extent of sections with different edge profiles. In either case, additional labor should be anticipated to tie into intersections or other areas requiring different edge profiles when paving using the Safety EdgeSM concept. The following provides an overview of the two options that were used on some of the demonstration projects.

If there are only a few intersecting roadways, driveways or limited areas where a vertical face is required along the edge of the pavement, the contractor can consider placing the safety edge using normal paving operations. The Safety EdgeSM is sawcut and removed to create a vertical edge. The sawing of the Safety EdgeSM can be completed at the same time the transverse joints are sawed. This option has worked fine, but does waste some PCC and requires additional sawing.
	Another option is to box out the areas requiring different edge profiles and place forms. The PCC in these limited areas is placed by hand using normal construction practices in order to tie into pavement intersections, driveways, and other features.*Vibration*

Generally, the standard spacing of the vibrators are sufficient to properly consolidate the fresh concrete at the Safety EdgeSM. Consolidation of the material within the Safety EdgeSM should be checked at the start of any project. If slip form pavers are not being used, hand vibrators need to be used to ensure that the PCC flows into the lower part of the Safety EdgeSM. As noted at the beginning of this section, all demonstration projects included the use of slip form pavers in construction the Safety EdgeSM.

*Curing*

Care should be taken to insure the specified curing procedures are properly followed for all surfaces at the edge of the pavement, including the Safety EdgeSM. The Safety EdgeSM, however, does not require any special curing requirements beyond that for typical PCC layers.

*Sawcutting*

Transverse control joint sawcutting can be stopped at the breakpoint of the Safety EdgeSM and not continued through the sloped surface of the edge. Experience shows the contraction cracks normally form at the end of the sawcut and extend through the Safety EdgeSM as planned (refer to Figure 16).
Figure 16. Sawcut and crack at the formed joint on one of the Safety EdgeSM demonstration projects.**Figure 16. Sawcut and crack at the formed joint on one of the Safety EdgeSM demonstration projects.**

4.5 Quality Measurement

The same properties used or identified by the owner agency to measure the quality of PCC pavement layers for acceptance should also be used on projects that include the Safety EdgeSM. The acceptance plan should not be modified for projects that include the Safety EdgeSM. More importantly, the air void content, strength, and/or smoothness requirements appropriate for a typical project should not be relaxed simply because the Safety EdgeSM is added to a PCC overlay or new construction project. Thus, the only difference between projects with and without the Safety EdgeSM is the slope of the edge itself.
      
  Book traversal links for SECTION 4: SPECIFIC CONSIDERATIONS FOR CONSTRUCTING THE Safety EdgeSM IN CONJUNCTION WITH NEW CONCRETE PAVEMENTS OR CONCRETE OVERLAYS
      ‹ SECTION 3: SPECIFIC CONSIDERATIONS FOR CONSTRUCTING THE SAFETY EDGESM IN CONJUNCTION WITH NEW AC PAVEMENTS OR AC OVERLAYS
                    Up
                    REFERENCES & APPENDICES ›
                
                Book:Safety EdgeSM Design and Construction Guide
              SI* (Modern Metric) Conversion Factors
                SECTION 1: INTRODUCTION
                SECTION 2: SAFETY EdgeSM – GENERAL DESIGN AND CONSTRUCTION CONSIDERATIONS
                SECTION 3: SPECIFIC CONSIDERATIONS FOR CONSTRUCTING THE SAFETY EDGESM IN CONJUNCTION WITH NEW AC PAVEMENTS OR AC OVERLAYS
                SECTION 4: SPECIFIC CONSIDERATIONS FOR CONSTRUCTING THE Safety EdgeSM IN CONJUNCTION WITH NEW CONCRETE PAVEMENTS OR CONCRETE OVERLAYS
                REFERENCES & APPENDICES 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