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FHWA Home / Safety / Safety EdgeSM Design and Construction Guide

Safety EdgeSM Design and Construction Guide


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.

Diagram showing SafetyEdge for PCC pavement with slope applied to approximately the top 5 inches with the slope range as steep as 1 vertical to 1.2 horizontal to as flat as 1 vertical to 2.0 horizontal. The angle of pavement lifts below the top 5 inches vary.
* Note, Recommended Rise to Run ratio range 1:1.2 to 1:2.0. The range of slope is equal to 26° to 40°.
Figure 14. Recommended Safety EdgeSM configuration for PCC pavements and overlays.

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.

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.

close-up photo of safety edge device attached to the paver shown from underneath.
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.


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.


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.


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).

photo of freshly cured PCC pavement with SafetyEdge that has been saw cut across the surface and crack has appropriately developed across the angle of the SafetyEdge and down the vertical edge all in alignment.
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.

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Page last modified on September 6, 2017
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