Safety EdgeSM

Demonstration Project

Seaford, Delaware

Field Report

January 30, 2011 
1. Report No. 2. Government Accession No 3. Recipient’s Catalog No

3. Title and Subtitle

Safety EdgeSM Project, Seaford, Delaware

5. Report Date

 January 30. 2011

6. Performing Organization Code

7. Authors

Harold Von Quintus and Jagannath Mallela 

8. Performing Organization Report No.

9. Performing Organization Name and Address

 Applied Research Associates, Inc.

 100 Trade Centre Drive, Suite 200

 Champaign, IL 61820

10. Work Unit No. 

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

 Office of Infrastructure

 Federal Highway Administration

 1200 New Jersey Avenue, SE

 Washington, DC 20590

13. Type of Report and Period Covered

 Report

 August 2010–January 2011

14. Sponsoring Agency Code

15. Supplementary Notes

Contracting Officer’s Technical Representative: Byron Lord and Mary Huie

Contracting Officer’s Technical Manager: Andy Mergenmeier

16. Abstract

In a coordinated effort with highway authorities and industry leaders, the Every Day Counts initiative serves as a catalyst to 

identify and promote cost effective innovations to bring about rapid change to increase safety of our nations highway 

system, decrease project delivery time, and protect our environment. The Safety EdgeSM concept is an example of one such 

initiative in which the edge of the road is beveled during construction for the purpose of helping drivers who migrate off the 

roadways to more easily return to the road without over correcting and running into the path of oncoming traffic or running 

off the other side of the roadway.

This field report documents the observations made on the construction of Safety EdgeSM on a two lane highway warm mix 

asphalt (WMA) overlay project near Seaford, Delaware. Safety EdgeSM paving devices from two manufacturers were 

demonstrated during this project. Details regarding the performance of each device along with the shape and physical 

properties of the finished Safety EdgeSM are presented for the purpose of understanding what processes and techniques were

most successful in forming the Safety EdgeSM. 

The findings from this overlay project and other similar ongoing projects form the basis for understanding the construction 

process and material performance necessary to bring this innovation into common highway practice and make our Nation’s 

highways safer. 

17. Key Words

Safety EdgeSM, Slope, WMA, Advant-Edger, 

TransTech Shoulder Wedge Maker 

18. Distribution Statement

No restriction. This document is available to the public 

through the Highways for LIFE website: 

http://www.fhwa.dot.gov/hfl/

Security Classif.(of this report)

Unclassified

19. Security Classif. (of this page)

Unclassified

20. No. of Pages

30 

21. Price

1 

FOREWORD

The purpose of this field report is to provide a summary of observations made during the warm 

mix asphalt (WMA) Safety EdgeSM project located along Old Furnace Road just northeast of 

Seaford, Delaware. These observations and data are to be used with similar information from 

other Safety EdgeSM projects to facilitate the development of standards and guidance for Safety 

EdgeSM construction and long term performance. 

All field and laboratory test results, WMA mixture design data, observations made during 

paving, and comments provided by construction personnel are included in the Field Evaluation 

Form that is provided as a separate document to this field report. This field report is a summary 

of the observations and field data measured during construction on August 25 to 27, 2010. In 

addition, it includes the results from field tests performed on a section that was paved on August 

19 and 20, 2010. 
2 

Table of Contents

Topic Page 

FOREWORD................................................................................................................................. 1

SUMMARY OF OBSERVATIONS ............................................................................................ 3

Overall Opinion of the Safety EdgeSM ..................................................................................... 3

Slope of the Safety EdgeSM ...................................................................................................... 3

Placement ................................................................................................................................ 3

Compaction ............................................................................................................................. 4

Shoulder Construction ............................................................................................................ 4

WMA Mixture and Safety EdgeSM ........................................................................................... 4

FIELD EVALUATION OF WMA OVERLAY WITH SAFETY EDGESM ........................... 5

INTRODUCTION ............................................................................................................................... 5

PAVEMENT STRUCTURE AND PROJECT CONDITIONS .................................................................... 5

FIELD EVALUATION........................................................................................................................ 9

Slope Measurements ............................................................................................................. 11

Cores ..................................................................................................................................... 12

Longitudinal Profile Measurements ..................................................................................... 16

OBSERVATIONS MADE DURING PAVING WITH SAFETY EDGESM ................................................ 16

Surface Preparation .............................................................................................................. 17

Placement/Paving Operations .............................................................................................. 17

Compaction Operations ........................................................................................................ 21

HMA Mixture Characteristics and the Safety EdgeSM .......................................................... 24

Other Observations ............................................................................................................... 28

FINDINGS AND CONCLUSIONS ...................................................................................................... 29

APPENDIX

DATA TABLES FROM FIELD MEASUREMENTS ........................................................................... A-2

PHOTOGRAPHS OF SELECTED CORES RECOVERED FROM THE PROJECT ................................ A-6
3 

SUMMAR Y OF OBSE R VAT IONS

This section of the report provides a summary and listing of important observations made during 

the paving operations, interview with paving personnel, and findings from the field 

measurements taken during paving that are expected to have a significant impact on the 

performance of this project. 

Overall Opinion of the Safety EdgeSM

• The Safety EdgeSM did not have a detrimental impact on the contractor’s paving 

operation during mainline paving. A couple of issues, however, were encountered that 

need to be resolved and are noted in the following bullet items. 

Slope of the Safety EdgeSM

• The average slope of the Safety EdgeSM was found to vary from 37 to 50° for the 

different sections. It was the opinion of construction personnel that the slope of the 

Safety EdgeSM device would need to be flattened to about 20 to 25° to meet the planned 

30° requirement.

Placement

• The Safety EdgeSM was formed using two devices at different times during paving; the 

TransTech Shoulder Wedge Maker device and the Advant-Edger device. The TransTech 

device was used to place warm mix asphalt (WMA) during the week of August 19. The 

Advant-Edger device was used during observations made for this field report. Both were 

properly bolted to the screed. The project superintendent commented that there was no 

difference between the two devices, but the screed operator commented that the AdvantEdger seemed to work better, resulting in a smoother edge condition. 

• Both contractor and agency personnel voiced a concern that paving across intersections 

or in areas with higher longitudinal profile; the Safety EdgeSM devices raise the screed 

relative to the profile set by the longitudinal ski. Both also commented that it was 

difficult to get a good tie-in to existing driveways and other hard surfaces. 
4 

Compaction 

• The WMA density or percent compaction of the Safety EdgeSM sections was found to be 

higher than for the non-Safety EdgeSM sections. Thus, the Safety EdgeSM is believed to 

have a confining effect on rolling an unconfined edge. This observation is considered a 

benefit to the use of the Safety EdgeSM. 

• The air voids of the interior WMA mat were considered good to fair with a mean value 

from 7.3 to 8.9 percent for the different sections. The air voids determined along the 

edge of the mat were high; varying from 8.6 to 13.5 percent. High air voids have a 

detrimental impact on pavement performance.

Shoulder Construction

• Existing fine to coarse-grained soil was planned to be used for the shoulder backing 

material. Placement of the backing material was not observed because the contractor 

planned to place it after all paving had been completed. 

WMA Mixture and Safety EdgeSM

• Longitudinal segregation or different surface texture was observed along the edge of each 

slat conveyor of the paver. 

• The planned WMA overlay thickness was 2.0 inches. The average overlay thickness for 

the Safety EdgeSM sections was found to vary from 2.0 to 2.7 inches. 

This Safety EdgeSM project should be monitored over time to determine its long-term

performance and the frequency of any required maintenance operations, as well as the life cycle 

cost of the Safety EdgeSM and its effectiveness over time. 
5 

FIE L D EVAL UATION OF WMA OVE R L AY WIT H SAFE T Y E DGE SM

I ntr oduction

A series of field tests were carried out to assess the placement and condition of the warm mix 

asphalt (WMA) overlay placed along Old Furnace Road just northeast of Seaford, Delaware, 

with and without the use of the Safety EdgeSM devices. The paving contractor for this project 

was American Infrastructure. The Contractor used the TransTech Shoulder Wedge Maker device 

during the first part of the project and the Advant-Edger device for the latter part. The purpose 

of this field study was to evaluate the quality of the in-place WMA mixture and Safety EdgeSM

by investigating three issues or features. 

1. Correct use of Safety EdgeSM device during paving. 

2. Safety EdgeSM versus non-Safety EdgeSM portions of project. 

3. Slope of the Safety EdgeSM. 

The location of the project was in Sussex County, as shown in Figure 1. The project started just 

east of the intersection between U.S. Highway 13 (Sussex Highway) and Old Furnace Road, and 

ended at the intersection between Old Furnace and Cokesbury Road; just west of Old Furnace. 

The Safety EdgeSM sections were located along the eastern portion of the project. 

Pavement Str uctur e and Pr oject C onditions

The project consisted of repairing some localized areas with extensive cracking and distortions, 

widening the roadway by 2 ft, and placing a 2-inch lift of a 9.5-mm WMA mix over the existing 

HMA pavement. Figure 2 shows the typical cracking and surface condition of the existing 

pavement along this project. Figure 3 provides a general view of the Figure 2 in WMA overlay 

and typical cross section of the pavement. In preparation for the WMA overlay, the following 

activities and repairs were made.

• The existing shoulder was graded along some areas of the project to remove grass and 

other debris (refer to Figure 4). 

• About 1 ft of HMA was placed to widen the roadway on each side (refer to Figure 5).

• Localized repairs or patches were placed in selected areas of the roadway where 

extensive cracking and distortions have occurred. 

• An emulsion tack coat was placed on the existing surface and patches (refer to Figure 5).

The ditches along the edge of the pavement were generally shallow (1 to 3 ft) with shallow 

slopes (10 to 30°). No lane-shoulder drop-offs were observed; however, the shoulder had been 

graded and the roadway widened on each side of the roadway prior to visiting the project. Figure 

3 through Figure 6 include general views of the roadway during construction. The Safety 

EdgeSM backing material was planned to be an on-site fine to coarse-grained soil. The backing 

material was scheduled to be graded back to the Safety EdgeSM near the end of this rehabilitation 

project, after paving. 
6 

Figure 1. Site location.

Figure 2. Typical condition of the existing surface (with tack coat applied).

Western 

project limit.

Eastern project 

limit.
7 

Figure 3. WMA overlay placed in the westbound lane. 

Planned 2.0 inch WMA 9.5 mm Overlay

24-Foot Roadway Width

HMA patch placed full roadway width in localized areas with very 

extensive cracking and distortions. 

Existing roadway widened by 1 ft on 

each side.
8 

Figure 4. Edge of pavement graded in some areas to remove grass and debris. 

Figure 5. 1.0-ft widening strip placed on both sides of the roadway. 

Pavement 

widening 
9 

Figure 6. General view of the roadway and right-of-way.

F ield E valuation 

Four sections were identified and marked during the paving operation; three Safety EdgeSM

sections and one section without the Safety EdgeSM device. Station numbers were unavailable 

for referencing the sections, so all sections were located related to telephone poles along the 

project. The following summarizes the four sections included within this project.

1. Area #1, Advant-Edger Safety EdgeSM section, westbound lane; telephone pole #44155, 

localized station numbers increase to the west from the designated telephone pole.

2. Area #2, Advant-Edger Safety EdgeSM section, westbound lane; telephone pole #44128, 

localized station numbers increase to the west from the designated telephone pole. 

3. Area #3, TransTech Shoulder Wedge Maker Safety EdgeSM section, westbound lane; 

telephone pole #44010, localized station numbers increase to the west from the 

designated telephone pole. 

4. Area #4, non-Safety EdgeSM section, westbound lane; telephone pole #44128. This nonSafety EdgeSM section was to be located on August 21, 2010, but the plant was not 

operating because of electrical problems. Thus, the section was located within Area #2 of 

the Advant-Edger. The non-Safety EdgeSM was designated along the centerline joint—

the opposite side of the paver without the Safety EdgeSM device.

Field tests were conducted within each test section for measuring slope and WMA density. 

Slope measurements were taken using a straight-edge (4-ft aluminum level) and 6-inch ruler 

(refer to Figure 7), while density readings were taken adjacent to and 3 ft from the mat’s edge 

using a Troxler 3430 nuclear density gauge (refer to Figure 8).
10 

Figure 7. Safety EdgeSM angle measurement.

Figure 8. Troxler 3430 nuclear density gauge used to measure WMA density. 

B

A

Toe of 

the slope 

Break point
11 

Eight cores were taken in the test sections established during the paving operation. The eight

cores were obtained at four different locations within the Safety EdgeSM sections. The cores 

were taken for calibration of the nuclear density gauge readings, and to observe the mix near the 

center of the mat and adjacent to the mat’s edge. Cores were planned for two other locations in 

the non-Safety EdgeSM section. However, paving on the last day of the field visit was cancelled 

because of electrical problems at the plant. The two cores used for acceptance (away from the 

edge) from the area designated as Area #2 were requested to increase the number of data points 

for determining the correction or adjustment factors between the nuclear density gauge and 

laboratory measured densities. Bulk specific gravities of these additional cores were not 

obtained. 

Slope Measurements 

Slope measurements were taken using a straight-edge to measure the width and thickness of the 

taper of the Safety EdgeSM; prior to any rolling and after final rolling. The average slope of the 

Safety EdgeSM sections is summarized in Table 1. 

Table 1. Summary of the Safety EdgeSM slope measurements. 

Section/Area Designation

Slope of Safety EdgeSM

Mean, degrees

Coefficient of

Variation, %

Prior to Rolling; mean of two areas 34.1 5.2

After Final Rolling

1 Advant-Edger 45.4 10.8

2 Advant-Edger 50.0 11.4

3 TransTech Shoulder Wedge Maker 36.6 24.3

The slope of the Safety EdgeSM prior to rolling the unconfined edge was 34.1°. The average 

slope for the Safety EdgeSM created with the TransTech device after final rolling was about the 

same as prior to rolling, while the slope for Advant-Edger section was much steeper after final 

rolling. The Safety EdgeSM created with the TransTech device was placed on August 19 or 20, 

and the Safety EdgeSM created with the Advant-Edger device was placed on August 25 and 26. 

The WMA mixture was observed to shove and “push out” under the steel wheel vibratory roller 

for the paving on August 26. The reason for the difference in Safety EdgeSM slopes between the 

two devices is unknown, but it was reported that the mixture did change and corrections to 

production had to be made between the two paving dates. In fact, the production plant was shut 

down on August 26 to make adjustments to the WMA mixture. 

The other important observation relates to the variability of the Safety EdgeSM slope 

measurements, as listed above. The coefficient of variation of the Safety EdgeSM slope created 

by the Advant-Edger device prior to any rolling was about half the value determined after final 

rolling. The coefficient of variation of the Safety EdgeSM slope for the TransTech device after 

final rolling was significantly greater than for the other sections. The reason for the higher 

variability but lower slope was unknown. 

All slope measurements are listed in Tables A-1 through A-3 of Appendix A. Figure 9 includes 

a comparison between the slope of the Safety EdgeSM after final rolling and thickness of the 
12 

Safety EdgeSM for the three sections. As shown, no correspondence between thickness and the 

slope of the Safety EdgeSM exists.

Figure 9. Comparison of the Safety EdgeSM slope and thickness of the WMA adjacent to the edge 

of the HMA overlay. 

Other slope measurements were made at random along the Safety EdgeSM in other areas of the 

project and the results were the same as for the specific Safety EdgeSM sections established for 

future performance reviews. Thus, the slope of the Safety EdgeSM was found to be steeper than 

what was planned. 

Cores 

A total of eight cores were drilled along the project. Two cores were taken at each station or 

location; in the same areas where the densities were measured with the Troxler nuclear density 

gauge. These cores were taken to measure the bulk specific gravity of the WMA for developing 

a correction factor for the nuclear density gauge readings taken adjacent to the edge and within 

the center of the mat. Figure 10 shows the location of the cores and nuclear density gauge 

readings relative to the edge of the WMA mat. Photographs of all eight cores recovered from the 

roadway are included in the appendix. A summary of these test results; core thickness and bulk 

specific gravities (saturated surface dry) converted to bulk densities is included in Table A-4 in 

Appendix A. Figure 11 is a comparison of the core densities taken along the edge and 3 ft from 

the edge (center of the steel drum breakdown roller) for the Safety EdgeSM sections. As 

expected, densities 3 ft from the edge are higher than along the edge of the mat (unconfined 

edge). 
13 

Figure 10. Photos showing location of cores and nuclear density tests made with the Troxler 

3430 gauge (nuclear density readings were taken and then the WMA mix was cored).

Core sets recovered from selected stations; "A" location 

is adjacent to the edge and "B" location is near the center 

of the steel drum roller (about 3 ft from the edge). 
14 

Figure 11. Comparison of core densities adjacent to the edge of pavement and 3 ft from the edge. 

Nuclear Density Results 

Density measurements were made with a Troxler 3430 gauge. Two readings were taken at each 

point; one with the gauge parallel and the other perpendicular to the centerline. Two points were 

marked at each station or location; one point adjacent to the Safety EdgeSM and the other 3-ft 

from the edge. 

Nuclear density gauge readings were taken before drilling each core. Figure 12 is a comparison 

of the nuclear gauge readings and densities measured on the cores. As shown, there is a positive 

bias for the readings taken adjacent to the edge of the mat. Adjustment factors were determined 

for the nuclear gauge readings taken at the edge of the mat and 3 ft from the edge. The 

adjustment factors are included in Table A-4 and the nuclear density gauge readings at each 

point are listed in Table A-5 and Table A-6 in Appendix A. The following summarizes the 

adjustment factors determined for this project. 

Location

Near Center of Steel Drum

Adjustment Factor

0.957

Adjacent to Safety EdgeSM 1.000

These factors were used to adjust the nuclear density gauge readings to be consistent with the 

densities that would be measured in the laboratory. The adjusted densities using the correction 

factors are included in Table A-5 and A-6 in Appendix A. 

Figure 13 shows a comparison of the adjusted nuclear density gauge readings taken adjacent to 

the Safety EdgeSM and 3 ft from the edge. Figure 13 also includes a comparison of the WMA air 

voids between both of these areas. As shown, the air voids are higher adjacent to the Safety 

EdgeSM, in comparison to 3 ft from the Safety EdgeSM. 
15 

Figure 12. Comparison of the nuclear gauge readings and densities measured on cores recovered 

from the WMA mat.

Figure 13. Comparison of the adjusted nuclear density readings and air voids between the areas 

adjacent to the edge and 3 ft from the edge. 

Nuclear densities 

measured in areas 

adjacent to the edge 

in comparison to 

those taken 3 ft from 

the edge (center of 

the roller). 

Air voids in areas 

adjacent to the edge 

in comparison to 

those taken 3 ft from 

the edge (center of 

the roller). 
16 

Figure 9 included a comparison between the WMA thickness (near the Safety EdgeSM) and slope 

of the Safety EdgeSM. The thickness of the WMA has little to no effect on the slope of the Safety 

EdgeSM. Figure 14 shows a comparison of the density and WMA overlay thickness. As shown, 

there is also little correspondence between the overlay thickness and air voids or densities. 

Figure 14. Comparison of WMA thickness at the edge of the mat and WMA air voids. 

Longitudinal Profile Measurements

Longitudinal profile measurements were not planned nor measured for this project. 

Observations M ade Dur ing Paving with Safety E dgeSM

This section discusses the observations made during the paving and rolling operations that could 

have a significant impact on the performance of the Safety EdgeSM over time. As stated in the 

Introduction to the Field Report section, the objective of this field study was to evaluate the 

quality of the in-place WMA material and Safety EdgeSM by investigating three features.

1. Correct use of Safety EdgeSM device during paving. 

2. Safety EdgeSM versus non-Safety EdgeSM portions of project. 

3. Slope of the Safety EdgeSM. 
17 

Surface Preparation

The following lists the different activities performed by the contractor prior to placing the WMA 

overlay. 

1. The edge of the pavement was graded to remove grass and other debris along the edge of 

the roadway prior to placing the overlay (refer to Figure 4).

2. The roadway was widened by 1 ft on each side (refer to Figure 5).

3. Localized WMA patches were placed in selected areas along the project where extensive 

cracking and surface distortions have occurred.

4. An emulsion tack coat was applied prior to the WMA overlay. The application of the 

tack coat was uniform and covered the entire surface (refer to Figure 5 and Figure 6).

Placement/Paving Operations

Figure 15 shows the equipment used to place the WMA overlay. The paving contractor operated 

the paver in the automatic longitudinal grade control mode and used non-contact sonic sensors 

for controlling the grade. The production plant was down for about 1.5 hours to make some 

WMA mixture revisions on August 26 to bring the mixture into specification. Free water was 

observed flowing from the back of a few truck beds. Excess water could explain some of the 

mixture tenderness characteristics observed during compaction (explained in the next section on 

Compaction Operations).

Figure 16 shows the Advant-Edger device attached to the screed. The project superintendent 

commented that there was no difference between the two devices, but the screed operator 

commented that the Advant-Edger seemed to work better than the TransTech device, resulting in 

a smoother edge condition. Figure 17 shows the slope and surface texture of the Safety EdgeSM; 

prior to and after rolling. 

Both contractor and agency personnel stated the Safety EdgeSM device would raise the screed 

relative to the profile set by the longitudinal ski when paving across intersections or in areas with 

higher longitudinal profile with hard surfaces. In addition, both commented that it was difficult 

to get a good tie-in to existing driveways and other hard surfaces. Figure 18 shows the line 

caused by the tip of the Safety EdgeSM device along the edge of pavement over an intersection 

driveway. 
18 

 

Figure 15. Equipment used to place the WMA overlay. 
19 

Figure 16. Advant-Edger device attached to the screed.
20 

Figure 17. Typical surface texture and slope of the Safety EdgeSM

Point of Safety EdgeSM device not 

on hard surface. 

Point of Safety EdgeSM device 

riding on hard surface of 

driveway. 

sections. 

Figure 18. Point of Safety EdgeSM scratching the surface of an intersecting driveway. 
21 

Compaction Operations

Figure 19 shows the two rollers that were used to compact the 9.5 mm WMA mixture. The 

primary or breakdown roller was a Volvo DD118 double drum steel wheel vibratory roller, while 

the finish roller was a Volvo DD112 double drum steel wheel vibratory roller. The field 

evaluation forms identify the number of passes and coverage used by all rollers (a pass is defined 

as one movement of the roller in one direction, while coverage is defined as each point on the 

mat receiving a pass of the roller). 

In summary, each roller performed seven passes with two coverages. The following summarizes 

the rolling pattern (number of passes and location for each roller) used by the contractor. 

• Breakdown or primary roller pattern; the roller’s vibratory setting was on high frequency and 

on setting 5 (on a scale of 1 to 10) for the amplitude: 

o First pass was along the Safety EdgeSM in the vibratory mode with the roller’s edge 

extended over the Safety EdgeSM by 4 to 6 inches. 

o Second pass; same location as for the first pass, but in the reverse direction and in 

vibratory mode. 

o Third pass was along the centerline construction joint in the vibratory mode with the 

roller’s edge extended over the longitudinal joint by 4 to 6 inches. 

o Fourth pass; same location as for the third pass, but in the reverse direction and in 

vibratory mode. 

o Fifth pass was down the center of the mat in vibratory mode. 

o Sixth pass; same location as for the fifth pass, but in the reverse direction and in 

vibratory mode. 

o Seventh pass was along the Safety EdgeSM in the vibratory mode with the roller’s 

edge extended over the Safety EdgeSM by 4 to 6 inches.

• Finish roller pattern; the roller’s vibratory setting was on high frequency and low amplitude: 

o First pass was along the Safety EdgeSM in the vibratory mode with the roller’s edge 

extended over the Safety EdgeSM by 4 to 6 inches. 

o Second pass; same location as for the first pass, but in the reverse direction and in 

vibratory mode. 

o Third pass was along the centerline construction joint in the vibratory mode with the 

roller’s edge extended over the longitudinal joint by 4 to 6 inches. 

o Fourth pass; same location as for the third pass, but in the reverse direction and in 

vibratory mode. 

o Fifth pass was down the center of the mat in vibratory mode. 

o Sixth pass; same location as for the fifth pass, but in the reverse direction and in 

vibratory mode. 

o Seventh pass along the Safety EdgeSM side of the mat in static mode. Additional 

passes that were needed based on periodic density measurements made with the 

nuclear density gauge were in the static position.

A control strip was not used to confirm that the roller pattern being used was achieving an 

adequate density of the mix. The Contractor used a Pavement Quality Indicator (PQI) nonnuclear density gauge to ensure that density was being met during paving. The non-nuclear and 
22 

nuclear density gauge readings and the densities of the cores suggest that adequate density was 

obtained for this mixture 3 ft from the edge, but the density was low near the edge. 

 

Figure 19. Rollers used for compacting the 9.5 mm WMA overlay mixture.

Figure 20 shows a comparison of the adjusted nuclear density gauge readings and air voids 

adjacent to the Safety EdgeSM in comparison to 3 ft from the edge. Table 2 summarizes the 

average air voids and slopes of the Safety EdgeSM for the different sections along this project, 

and is followed by the following important points from these density and slope measurements: 

Volvo double drum 

vibratory steel 

wheel roller used in 

breakdown or 

primary position for 

compacting the 

WMA overlay. 

Volvo double drum 

vibratory steel 

wheel roller used in 

the vibratory and 

static mode that was 

used in the finish 

position for 

compacting the 

WMA overlay.
23 

Figure 20. Comparison of volumetric properties between the areas adjacent to the edge and 3 ft 

from the edge (center of the steel drum roller) for the different sections.

Table 2. Summary of the average slope and air voids. 

Section Identification Average 

Slope 

Air Voids at 

Edge

Air Voids near 

Mat Center

Mean COV Mean COV

Non-Safety EdgeSM Section --- 13.5 28.9 8.92 24.2 

Area #1; Advant Section 45.4 8.6 30.7 7.3 19.3 

Area #2; Advant Section 50.0 9.4 33.4 7.6 28.3 

Area #3; TransTech Section 36.6 11.2 13.1 8.4 12.3 
24 

• The air voids measured along the mat’s edge of the Safety EdgeSM sections are 

significantly lower than measured along the non-Safety EdgeSM section. The Safety 

EdgeSM provided additional confinement along the edge.

• The air voids measured along the mat’s edge of the Advant-Edger Safety EdgeSM sections 

are slightly higher than measured within the center of the Volvo double drum steel wheel 

roller. It was expected that the extra pass of the roller along the Safety EdgeSM provides 

additional densification of the mix.

• The other important observation was the difference between the Advant-Edger and 

TransTech sections. The TransTech section had higher air voids but lower slopes in 

comparison to the Advant-Edger sections. The reason for this difference was unknown, 

because the roller pattern used to compact the TransTech section was not recorded during 

placement. Two additional roller passes (one for each of the rollers) along the Safety 

EdgeSM was used to compact the Advant-Edger sections. It was expected that this 

additional pass increased the density (lower air voids) but steepened the slope. 

HMA Mixture Characteristics and the Safety EdgeSM

The WMA mixture design data was obtained from the Delaware DOT. The WMA mixture 

design parameters are documented in the Field Evaluation Form, which is a separate document to 

this field report. This WMA includes 21 percent Recycled Asphalt Pavement (RAP) and 6 

percent shingles.

The WMA mixture volumetric properties and gradation were considered reasonable. Figure 21

shows the surface texture of the finished HMA mat along different areas of the project; with and 

without surface defects or surface texture differences. The surface texture and condition were

relatively uniform within specific areas of the project. Some agency personnel voiced a concern 

about the use of some Superpave mixtures; they can be very tender and move under steel wheel 

rollers. 

The WMA mixture did shove and “push out” during the compaction operation, steepening the 

slope of the Safety EdgeSM. The WMA mixture exhibited tenderness under the steel wheel 

rollers. As an example, roller marks were present after the breakdown roller completed its rolling 

pattern, checking was observed during the rolling operation, and shear cracks were observed 

along the roller’s edge (Figure 22 shows these examples). Chatter from the Volvo breakdown 

roller was observed in those areas exhibiting the more severe checking and shear cracks (refer to 

Figure 22).

The temperature of the WMA delivered to the project site was reported to be approximately 

260 °F and 160 to 170 oF during finish rolling. In some cases, the WMA temperature was below 

150 oF during the last pass of the finish roller. The WMA temperature could be related to the 

roller marks being left in the mat, checking and chatter observed in specific areas, and the steeper 

slopes than planned. 

Longitudinal segregation or surface texture difference was observed along the edges of the slat 

conveyor (refer to Figure 23). Bulk mixture samples (for gradation testing), nuclear gauge 
25 

density tests, and cores were not taken within these locations. 
26 

Figure 21. Surface texture of the overlay after final rolling.

Example showing an area 

with a tight surface, fine 

texture of the mat; small 

surface voids.

Example showing an area 

with a coarse surface texture 

of the mat; large surface 

voids. 

Example showing an area 

with localized crushed 

aggregate at the surface of 

the mat.
27 

 

Figure 22. Surface defects observed after rolling. 

Roller marks 

from the 

vibratory roller.

Checking and shear 

crack along the edge 

of the roller.

Chatter left on the surface 

from the vibratory roller.
28 

Figure 23. Longitudinal segregation or surface texture differences along the edge of both slat 

conveyors. 

Thus, it was not confirmed whether these areas shown in Figure 23 were caused by segregation 

or surface texture difference near the surface. It was expected that these areas were a result of 

longitudinal segregation along the edges of the slat conveyor of the paver. Densities were taken 

with the nuclear density gauge for the non-Safety EdgeSM section near the area in question and 

some of these densities were found to be low (and high air voids). 

The distance between the end of the auger and screed end plate was approximately 24 inches

(refer to Figure 15 and Figure 16). This distance should be less than 18 inches. The distance 

between the end of the auger and screed end plate was not believed to be a contributing factor to 

the steeper slope. 

Other Observations

The following lists the observations and comments made by construction personnel and on-site 

personnel. 

Surface texture 

difference along the 

outside edge of the slat 

conveyor. 

Surface texture 

difference along the 

outside edge of the slat 

conveyor. 
29 

• A shallower angle of the Safety EdgeSM device will be needed to meet the planned 30°

angle.

• There were different opinions on the use of the two Safety EdgeSM devices (AdvantEdger and TransTech). One opinion was that there was no difference between two 

devices, while another opinion was that the Advant-Edger device resulted in a smoother 

edge.

• The densities measured along the Safety EdgeSM created by the TransTech device were 

consistently lower than those measured along the edge created by the Advant-Edger 

device. However, the densities measured within the center of the mat (away from the 

Safety EdgeSM) are also higher for the Advant-Edger section (about 147 pounds per cubic 

foot (pcf)) in comparison to the TransTech section (145 pcf). This observation indicates 

that this difference is more related to the rolling pattern and/or WMA mixture between 

the different days of paving rather than related to the Safety EdgeSM devices. 

• Some construction personnel voiced an opinion that the planned 30° slope of the Safety 

EdgeSM will not be met using Superpave designed mixtures that are tender. 

• After the evaluation, the Delaware DOT management stated that overlays greater than 

1.25 inch will have the Safety EdgeSM. 

• Paving across driveways and other features with hard surfaces causes the screed to rise 

resulting in a reduction of smoothness in localized areas. 

F indings and C onclusions

As previously stated, the objective of this field study was to evaluate the quality of the in-place 

WMA material and Safety EdgeSM by investigating three features.

1. Correct use of Safety EdgeSM device during paving. 

2. Safety EdgeSM versus non-Safety EdgeSM portions of project. 

3. Slope of the Safety EdgeSM. 

This section of the field report summarizes the findings and conclusions made during the 

paving/compaction operations related to the long term performance of the WMA mixture and 

Safety EdgeSM. 

• The average slope of the Safety EdgeSM from the TransTech Shoulder Wedge Maker 

device was 36°, while it was 45 and 50° for the Advant-Edger device; both exceeding the 

planned value of 30°. It was expected that the slope of the Safety EdgeSM device may 

need to be reduced to a value of about 25° to end up with a 30° slope after rolling.

• The average air voids along the edge of the mat were lower for the Safety EdgeSM than 

for the non-Safety EdgeSM section. The reason for this decrease in air voids and increase 
30 

in density was believed to be related to the added confinement from the Safety EdgeSM

material. This observation is considered a benefit from the use of the Safety EdgeSM. 

• Breakdown and finish rolling did steepen the slope of the Safety EdgeSM, especially 

during the paving operations on August 25 and 26. It was expected that the magnitude of 

this increase will be mixture dependent. There was much less of an increase in slope 

during the previous week’s paving. The reason for the increase in the slope of the Safety 

EdgeSM during paving on August 25 and 26 was probably related to the tenderness of the 

WMA, as discussed above. Mix behavior under the steel wheel rollers was not observed 

during the week of August 19. 

• WMA thickness variations measured along the sections had no impact on the slope of the 

Safety EdgeSM or the density adjacent to the Safety EdgeSM. 

The pavement should be inspected after the final shoulders have been constructed. Local soil is 

planned to be used as the backing material for the Safety EdgeSM. Care should be taken to 

observe the material placement and ensure that meets proper relative elevation to the WMA mat. 

Long term monitoring of the shoulder should be performed to see how well the fine- to coarsegrained shoulder material remains in place and observe any deformation or erosion. 
A-1 

APPE NDIX A 

DAT A T ABL E S AND COR E PHOT OGR APHS 
A-2 

DAT A T ABL E S FR OM FIE L D ME ASUR E ME NT S

This section of the field report provides a summary and listing of all field measurements 

recorded during the paving operations. These data are also included in the detailed evaluation 

forms for the Safety EdgeSM projects.

Table A-1. Safety EdgeSM slope measurements for sections placed with the Advant-Edger device 

after final rolling. 

Core/Section ID Station

Safety Edge

Section Identifier Width of Taper Thickness Slope

Area #1; Telephone Pole #44155; Advant-Edger

Core #1 0+50 2.125 1.75 39.5

1+00 2 2 45

1+50 1.5 2 53.1

2+00 2.125 2.4375 48.9

Core #2 2+50 2.375 2.25 43.5

3+00 2.5 2 38.7

3+50 2 2.3125 49.1

4+00 2.375 2.375 45

Mean Value 2.13 2.14 45.35

Standard Deviation 0.313 0.238 4.911

Coefficient of Variation 14.75 11.12 10.83

Area #2; Telephonee Pole #44128; Advant-Edger

1+00 1.5 1.875 51.3

1+50 2.125 2.125 45

2+00 1.875 1.875 45

Core #3 2+50 1.75 2.25 52.1

3+00 1.875 2.5 53.1

3+50 2 2.125 46.7

4+00 1.875 2.25 50.2

4+50 1.25 2.375 62.2

Core #4 5+00 2.625 2.375 42.1

5+50 1.75 2.25 52.1

Mean Value 1.863 2.200 49.980

Standard Deviation 0.365 0.206 5.699

Coefficient of Variation 19.6 9.4 11.4
A-3 

 

Table A-2. Safety EdgeSM slope measurements for sections placed with the TransTech shoulder 

wedge maker device after final rolling. 

Section Identifier Core/Section ID Station

Safety Edge

Width of Taper Thickness Slope

Area #3; Telephone Pole #44010; TransTec Device; HMA 

Placed August 19 or 20, 2010

0+00 1.625 1.625 45

0+25 3.5 1.875 28.2

0+50 2.875 1.875 33.1

0+75 2.5 2 38.7

1+00 3.5 2 29.7

1+25 3.5 2.5 35.5

1+50 2.5 2.25 42

1+75 3.75 2.375 32.3

2+00 3.125 1.875 31

2+25 3.125 2 32.6

2+50 3.25 1.875 30

2+75 3.25 2.125 33.2

3+00 1.875 2.125 62.1

3+25 3.375 2 30.7

3+50 2.125 2.125 45

Mean Value 2.925 2.042 36.61

Standard Deviation 0.653 0.220 8.914

Coefficient of Variation 22.3 10.8 24.3

Table A-3. Safety EdgeSM slope measurements for sections placed with the Advant-Edger 

device; prior to rolling. 

Section Identifier Core/Section ID Station

Safety Edge

Width of Taper Thickness Slope

Area #1; East of German Road; Slope Measurements Prior 

to Rolling

A 4 2.6 33.2

B 4.13 2.68 32.9

C 3.74 2.72 36

D 3.54 2.68 37.1

Mean Value 3.85 2.67 34.80

Standard Deviation 0.264 0.050 2.074

Coefficient of Variation 6.85 1.89 5.96

Area #2; West of German Road; Slope Measurements Prior 

to Rolling

E 4 2.625 33.3

F 4.125 2.5 31.2

G 4.25 2.625 31.7

H 3.75 2.625 35

I 3.75 2.4375 33

Mean Value 3.975 2.563 32.84

Standard Deviation 0.224 0.088 1.491

Coefficient of Variation 5.6 3.4 4.5
A-4 

Table A-4. Nuclear density adjustment ratios; core density/nuclear 

density. 

Area/Location Core # Lane Direction Station Type of Section

Density of Cores Nuclear Density Values Adjustment Ratio Adjusted Nuclear Values

A – Adjacent to 

Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

Area #1; Telephone Pole 

#44155

C 1 Westbound 0+50 Advant-Edger 142.20 150.40 142.20 158.00 1.000 0.952 145.90 159.42

C 2 Westbound 2+50 Advant-Edger 138.80 149.30 143.90 151.00 0.965 0.989 147.64 152.36

Area #2; Telephone Pole 

#44128

C 3 Westbound 2+50 Advant-Edger 142.10 149.90 135.80 156.40 1.046 0.958 139.33 157.81

C 4 Westbound 5+00 Advant-Edger 139.80 148.50 141.20 160.20 0.990 0.927 144.87 161.64

C T-1 Westbound 0+95 Advant-Edger

C T-2 Westbound 2+32 Advant-Edger

CT-3 Westbound Advant-Edger

CT-4 Westbound Advant-Edger

Average 140.725 149.525 140.775 156.400 1.000 0.957 144.435 157.808

Standard Deviation 1.696 0.818 3.499 3.923 0.034 0.025 3.590 3.958

Coefficient of Variation 1.21 0.55 2.49 2.51 3.42 2.66 2.49 2.51

Table A-5. Density readings made with a nuclear density gauge (Troxler Gauge 3430) for the 

sections placed with the Advant-Edger device. 

Core Lane Direction Station Type of Section Nuclear Densities Adjusted Nuclear Values Air Voids, %

Location A – Adjacent to B – 3 feet from A – Adjacent B – 3 feet from HMA A – Adjacent B – 3 feet 

Location/Area

C 1 Westbound 0+50

Westbound 1+00

Westbound 1+50

Westbound 2+00

Area #1; Safety Edge Section; C 2 Westbound 2+50

Telephone Pole # 44155 Westbound 3+00

Westbound 3+50

Westbound 4+00

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Average Value

Standard Deviation

Edge Edge

142.15 157.95

144.45 155.5

146.55 155.3

140.35 151.45

143.9 151

144.85 156

152.3 154.45

151.35 153.5

145.74 154.39

4.191 2.338

to Edge Edge

142.15 151.15815

144.45 148.8135

146.55 148.6221

140.35 144.93765

143.9 144.507

144.85 149.292

152.3 147.80865

151.35 146.8995

145.74 147.75

4.191 2.237

Thickness, in.

1.75

2

2

2.4375

2.25

2

2.3125

2.375

2.141

0.238

to Edge from Edge

10.81 5.15

9.36 6.62

8.04 6.74

11.93 9.06

9.71 9.33

9.11 6.32

4.44 7.25

5.03 7.82

8.55 7.29

2.630 1.404

30.74 19.26

Air Voids, %

A – Adjacent B – 3 feet 

Core Lane Direction Station

Coefficient of Variation

Type of Section

2.88 1.51

Nuclear Densities

2.88 1.51

Adjusted Nuclear Values

11.12

Location A – Adjacent to B – 3 feet from A – Adjacent B – 3 feet from HMA 

Location/Area

Westbound 1+00

Westbound 1+50

Westbound 2+00

C 3 Westbound 2+50

Area #2; Safety Edge Section; Westbound 3+00

Telephone Pole #44128 Westbound 3+50

Westbound 4+00

Westbound 4+50

C 4 Westbound 5+00

Westbound 5+50

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Advant

Average Value

Standard Deviation

Coefficient of Variation

Edge Edge

144.75 152.05

144 151.4

142.1 151.9

135.8 156.35

143.1 153.45

147.7 153.85

147.9 148.7

153.55 157.7

141.15 160.2

144.45 153.96

4.983 3.554

3.45 2.31

to Edge Edge

144.75 145.51

144.00 144.89

142.10 145.37

135.80 149.63

143.10 146.85

147.70 147.23

147.90 142.31

153.55 150.92

141.15 153.31

144.45 147.34

4.983 3.401

3.45 2.31

Thickness, in.

1.875

2.125

1.875

2.25

2.5

2.125

2.25

2.375

2.375

2.25

2.20

0.206

9.36

to Edge from Edge

9.17 8.70

9.64 9.09

10.84 8.79

14.79 6.11

10.21 7.85

7.32 7.61

7.20 10.71

3.65 5.30

11.43 3.80

9.36 7.55

3.127 2.134

33.40 28.26

Overall Average 2.555 159.432

TransTech Device Max. Specific 2.548 158.995

Advant Device Gravity: 2.554 Max. Density: 159.370

Adjustment Ratios for Nuclear 

Gauge:

A= 1

B= 0.957
A-5 

Table A-6. Density readings made with a nuclear density gauge (Troxler Gauge 3430) for the 

section placed with the TransTech Shoulder Wedge Maker device and the section without the 

Safety EdgeSM. 

Nuclear Densities Adjusted Nuclear Values Air Voids, % Core Location/Area Lane Direction Station Type of Section A – Adjacent to B – 3 feet from A – Adjacent B – 3 feet from HMA A – Adjacent B – 3 feet Location Edge Edge to Edge Edge Thickness, in. to Edge from Edge

Westbound 0+00 TransTec 140.95 154.4 140.95 147.76 1.625 11.35 7.07

Westbound 0+50 TransTec 142.6 153.65 142.60 147.04 1.875 10.31 7.52

Westbound 1+00 TransTec 140.9 152.55 140.90 145.99 2 11.38 8.18

Westbound 1+50 TransTec 139.8 152.3 139.80 145.75 2.25 12.08 8.33 Area#3; Safety Edge Section; Westbound 2+00 TransTec 140.5 152.15 140.50 145.61 1.875 11.64 8.42 Telephone Pole #44010; HMA Westbound 2+50 TransTec 140.1 149.2 140.10 142.78 1.875 11.89 10.20 Placed August 19 or 20, 2010 Westbound 3+00 TransTec 134.6 150.1 134.60 143.65 2.125 15.35 9.66

Westbound 3+50 TransTec 142.2 152.8 142.20 146.23 2.125 10.57 8.03

Westbound 4+00 TransTec

Average Value 140.21 152.14 140.21 145.60 1.97 11.82 8.43

Standard Deviation 2.462 1.725 2.462 1.651 0.198 1.548 1.038

Coefficient of Variation 1.76 1.13 1.76 1.13 10.04 13.10 12.32

Nuclear Densities Adjusted Nuclear Values Air Voids, % Core Location/Area Lane Direction Station Type of Section A – Adjacent to B – 3 feet from A – Adjacent B – 3 feet from HMA A – Adjacent B – 3 feet Location Edge Edge to Edge Edge Thickness, in. to Edge from Edge

Westbound 0+00 Non-Safaety Edge 154.6 147.95 7.16

Core T-1 Westbound 0+45 Non-Safaety Edge 133.5 150.7 133.50 144.22 16.23 9.51

Area #4; Non-Safety Edge; Along Westbound 0+95 Non-Safaety Edge 140.8 150.65 140.80 144.17 11.65 9.54

the Centerline of Roadway; Plant Core T-2 Westbound 1+45 Non-Safaety Edge 143.6 157.2 143.60 150.44 9.90 5.60

down so section located along Westbound 2+32 Non-Safaety Edge 129.3 149.65 129.30 143.22 18.87 10.14

the centerline of previously Westbound 2+82 Non-Safaety Edge 142.35 147.25 142.35 140.92 10.68 11.58

placed mix from yesterday; Westbound Non-Safaety Edge

Telephone Pole #44128. Westbound Non-Safaety Edge

Westbound Non-Safaety Edge

Average Value 137.91 151.68 137.91 145.15 #DIV/0! 13.47 8.92

Standard Deviation 6.205 3.599 6.205 3.444 #DIV/0! 3.894 2.161

Coefficient of Variation 4.50 2.37 4.50 2.37 #DIV/0! 28.92 24.23
A-6 

Photogr aphs of Selected C or es R ecover ed fr om the Pr oject

This section of the field report provides a photograph of the cores that were recovered for 

laboratory density testing, and visual observations of the mixture along the edge and 3 feet from 

the edge. No systematic visual differences were noted between the different core sets. 

Cores 1B (3 ft from edge) 

and 1A (adjacent to edge) Cores 2B (3 ft from edge) 

and 2A (adjacent to edge) 
A-7 

Cores 3B (3 ft from edge) 

and 3A (adjacent to edge) Cores 4B (3 ft from edge) 

and 4A (adjacent to edge)