Safety Edge SM

Demonstration Project 

Elizabethtown, 

Pennsylvania 

Field Report 

May 24, 2011 
FOREWORD 

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

mix asphalt (HMA) Safety EdgeSM project located near Elizabethtown, Pennsylvania. 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, HMA mixture design information and 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 collected during construction on July 

6, 7, and 8, 2010 to evaluate the use of the Safety EdgeSM during paving, compare Safety 

EdgeSM and non-Safety EdgeSM portions along the project, determine the slope of the Safety 

EdgeSM, recommend adjustments to the Safety EdgeSM design if found to be needed, and 

identify benefits and complications with the use of the Safety EdgeSM device. 
ii

1. Report No. 2. Government Accession No 3. Recipient’s Catalog No

3. Title and Subtitle 

Safety EdgeSM Project, Elizabethtown, Pennsylvania 

5. Report Date 

 May 24. 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 

15. Supplementary Notes 

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

Contracting Officer’s Technical Manager: Andy Mergenmeier 

13. Type of Report and Period Covered 

 Field Report 

 July 2010–May 2011

14. Sponsoring Agency Code 

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 hot mix 

asphalt (HMA) overlay project near Elizabethtown, Pennsylvania. The Advant-Edger device was demonstrated during this 

project. Details regarding the performance of the 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, HMA, Advant-Edger 

18. Distribution Statement 

No restriction. 

19. Security Classif.(of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

26 

22. Price 

Form DOT F 1700.7 (8-72)
iii

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

(none) mil 25.4 micrometers μm

in inches 25.4 millimeters mm

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km

AREA 

in2square inches 645.2 square millimeters mm2

ft2square feet 0.093 square meters m

2

yd2square yards 0.836 square meters m

2

ac acres 0.405 hectares ha

mi2square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 millimeters mL 

gal gallons 3.785 liters L 

ft3cubic feet 0.028 cubic meters m

3

yd3cubic yards 0.765 cubic meters m

3

NOTE: volumes greater than 1000 L shall be shown in m3

MASS 

oz ounces 28.35 grams g 

lb pounds 0.454 kilograms kg 

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) 

°F Fahrenheit 5 (F-32)/9 

or (F-32)/1.8 

Celsius °C

ILLUMINATION 

fc foot-candles 10.76 lux lx

fl foot-Lamberts 3.426 candela per square meter cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 Newtons N 

lbf/in2 (psi) poundforce per square inch 6.89 kiloPascals kPa 

k/in2 (ksi) kips per square inch 6.89 megaPascals MPa 

DENSITY 

lb/ft3 (pcf) pounds per cubic foot 16.02 kilograms per cubic meter kg/m3

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

μm micrometers 0.039 mil (none) 

mm millimeters 0.039 inches in

m meters 3.28 feet ft

m meters 1.09 yards yd

km kilometers 0.621 miles mi

AREA 

mm2square millimeters 0.0016 square inches in2

m

2

square meters 10.764 square feet ft2

m

2

square meters 1.195 square yards yd2

ha hectares 2.47 acres ac

km2square kilometers 0.386 square miles mi2

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m

3

cubic meters 35.314 cubic feet ft3

m

3

cubic meters 1.307 cubic yards yd3

MASS 

g grams 0.035 ounces oz 

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE 

°C Celsius 1.8C+32 Fahrenheit °F

ILLUMINATION 

lx lux 0.0929 foot-candles fc

cd/m2candela per square meter 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N Newtons 0.225 poundforce lbf 

kPA kiloPascals 0.145 poundforce per square inch lbf/in2 (psi) 

MPa megaPascals 0.145 kips per square inch k/in2 (ksi) 

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 

2003) 
iv

Table of Contents 

Page 

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

SUMMARY OF OBSERVATIONS ............................................................................................ 1

Overall Opinion of the Safety EdgeSM ..................................................................................... 1

Slope of the Safety EdgeSM ...................................................................................................... 1

Placement ................................................................................................................................ 1

Compaction ............................................................................................................................. 2

Shoulder Construction ............................................................................................................ 2

HMA Mixture and the Safety EdgeSM ...................................................................................... 2

FIELD EVALUATION OF HMA OVERLAY WITH SAFETY EDGESM ............................ 3

INTRODUCTION ...............................................................................................................................

PAVEMENT STRUCTURE AND PROJECT CONDITIONS .................................................................... 3

FIELD EVALUATION........................................................................................................................ 8

Slope Measurements ............................................................................................................... 9

Cores..................................................................................................................................... 11

Nuclear Density Results ........................................................................................................ 12

OBSERVATIONS MADE DURING PAVING WITH THE SAFETY EDGESM ........................................ 15

Surface Preparation Issues ................................................................................................... 15

Placement/Paving Operations .............................................................................................. 16

Compaction Operations........................................................................................................ 22

HMA Mixture Characteristics and the Safety EdgeSM .......................................................... 25

 3

FINDINGS AND CONCLUSIONS ...................................................................................................... 27

APPENDIX A. DATA TABLES FROM FIELD MEASUREMENTS ............................... A-1
1

SUMMARY OF OBSERVATIONS 

This section of the field 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 the Safety EdgeSM and non-Safety EdgeSM portions of this project. 

Overall Opinion of the Safety EdgeSM

The Safety EdgeSM did not have a detrimental impact on the agency’s paving operation

during mainline paving. Some issues, however, were encountered that need to be resolved. 

These are noted in some of the following bullet items. 

Slope of the Safety EdgeSM

 The average slope of the Safety EdgeSM was found to be 48°. Only one slope 

measurement was found to be less than 40°. 

 Based on observations during paving, the 9.5 mm HMA mix behind the screed appeared 

similar in shape with and without the Safety EdgeSM device. In addition, the coarse 

aggregate at the bottom of the Safety EdgeSM were loose and could be easily removed, 

which is similar to sections without the Safety EdgeSM device. 

Placement 

 The Safety EdgeSM was formed using the Advant-Edger device, which was properly 

bolted to the screed of the paver. Construction personnel recommended that the Safety 

EdgeSM device include an automated system for raising and lowering the device. 

 A goal of this project was to maximize pavement width. The Safety EdgeSM was added 

to the project after it was designed. In several areas where paving extended beyond the 

HMA base, the material upon which the Safety EdgeSM was placed had not been prepared 

prior to paving. In these areas, the Safety EdgeSM was placed over grass and other loose 

debris along the edge of the pavement. It is expected that the Safety EdgeSM within these 

areas may break off from the mat with minimal operations of local traffic along the edge. 

Preparing the edge prior to placing the Safety EdgeSM is believed to be important for 

future performance. 

 The Safety EdgeSM did create some minor problems for the paving crew at times. This 

was particularly apparent at intersections, driveways, and changes in longitudinal 

elevations or profile. It was difficult for the screed operator to adjust four parameters at 

the same time; raising or lowering the Safety EdgeSM device, adjusting the height of the 

screed end plate, extending or retracting the screed extension, and adjusting the height of 

the screed. It is expected that an automated system could eliminate or reduce these 

problems. 

 When used per manufacturer’s recommendation, the Safety EdgeSM device exerts a 

downward pressure that keeps the bottom of the device in contact with the surface being 

paved. In some areas, the Safety EdgeSM hung up on some of the coarse aggregate 

particles of the HMA base mix that was used to widen each side of the roadway. When 
2

this occurred the screed would vibrate or exhibit a jerking mode. If excessive downward 

pressure is used, the screed will no longer operate under the principle of a free floating 

screed that is important for placing HMA. Thus, monitoring the downward pressure is 

important. 

Compaction 

 The HMA mix density was higher and the air voids lower adjacent to the edge of the mat 

for the Safety EdgeSM sections in comparison to the non-Safety EdgeSM section. Thus, 

the Safety EdgeSM was believed to have a confining effect on rolling an unconfined edge 

condition. This observation is considered a benefit to the use of the Safety EdgeSM.

 The air voids of the HMA mat interior and along the Safety EdgeSM varied from 8 to 

over 18 percent. This air void content is higher than desirable for long term performance. 

Shoulder Construction 

 HMA millings are planned to be used for the backing material. Placement of the backing 

material was not observed, because the millings are to be placed later this construction 

season. 

HMA Mixture and the Safety EdgeSM

 No segregation was observed in any of the areas of the mat or Safety EdgeSM. 

 The screed end plate did plow up some dirt and grass in selected areas when the Safety 

EdgeSM material was extended beyond the HMA base mix used to widen the roadway. 

When this occurred dirt and grass were pushed into the 9.5 mm HMA mix being placed 

by the paver. This contamination of the HMA mix will have a detrimental impact on its 

performance, especially near an unconfined edge with low densities and high air voids. 

 The planned HMA overlay thickness was 1.5 inches. The overlay thickness of the cores 

was found to vary from 1.2 to 2.4 inches along the outside edge of the project. 

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. 
3

FIELD EVALUATION OF HMA OVERLAY WITH SAFETY EDGESM

Introduction 

A series of field tests were carried out to assess the placement and condition of an HMA 

overlay along State Road 2009 (Bellaire Road) near Elizabethtown, Pennsylvania, with and 

without the use of the Safety EdgeSM device. The objective or purpose of this field study was 

to evaluate the quality of the in-place HMA material and Safety EdgeSM by investigating 

three issues or features. 

1. Correct use of the Safety EdgeSM device during paving. 

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

3. Slope of the Safety EdgeSM. 

The Safety EdgeSM device attached to the screed for this project was the Advant-Edger. The 

location of the project is shown in Figure 1. The project started at the intersection with 

Colebrook Road or State Route 341 and ended at the bridge for Conewago Creek. The speed 

limit for this section of roadway was 40 mph. The paving crew for this project consisted of 

Pennsylvania Department of Transportation (DOT) personnel. 

Pavement Structure and Project Conditions 

The project consisted of placing a 1.5 inch lift of a 9.5 mm HMA mix over the existing HMA 

pavement. Pennsylvania DOT project personnel indicated that another 1.5 inch HMA lift 

may be placed in the next year or two. The existing pavement was widened to include twotwelve foot lanes. Figure 2 provides a general view of the 1.5 inch HMA overlay, and typical 

cross section of the pavement. 

The ditches along the edge of the pavement were generally shallow or almost level with the 

existing pavement (refer to Figure 2), with the exception of a few areas (refer to Figure 3). 

An HMA base mix had already been placed on both sides of the road to widen the roadway. 

Some areas had narrow ditches that were approximately one to two feet in depth, but were 

covered or hidden in grass. 

The Safety EdgeSM backing material is planned to be HMA millings. This backing material 

was planned to be placed in the future and was not stored on the project site. More 

importantly, there are many areas where placing the HMA millings will be difficult because 

of the edge/shoulder condition (refer to Figures 2 and 3). 

As noted above, the existing pavement was widened on both sides by about 1 foot, by placing 

an HMA base mix (refer to Figure 4). The HMA base mix had already been placed along the 

pavement’s edge. The surface of this material was rough, as shown in Figures 4 and 5. The 

width of the pavement varied significantly along the project because of site features and 

driveways that exist along the project (refer to Figures 3 and 6). 
4

Figure 1 – Location of site. Project starts at the intersection between ColeBrook Rd. and 

Bellaire Rd. and proceeds south to the bridge at Conewago Creek. 

Project Ends at Bridge 

for Conewago Creek. 

Project Starts 

at Intersection. 
5

The Safety 

EdgeSM was over 

the HMA base in 

some areas and 

over grass or soil 

in other areas. 

1.5 inch HMA 9.5 mm Overlay 

Existing HMA Pavement 

3-foot wide 6 inch depth of HMA Base used to widen both sides of 

roadway; total roadway width equals 24 feet. 

Figure 2. General overview of the 1.5 inch HMA layer placed along the project and 

pavement cross section provided by the Pennsylvania DOT. 
6

Figure 3. Localized area with deep ditches adjacent to the pavement. 

6-inch HMA 

base placed 3 

feet wide along 

both edges of 

the existing 

pavement to 

widen the 

roadway to 24 

feet (refer to 

Figure 2). The 

width of this 

material varied 

along the 

project. 

Edge of mat along the 

deep ditch which only 

received one roller 

pass, because of the 

drop-off and loss of 

support along the edge. 

No densities were 

measured within this 

area. 

Figure 4. Additional HMA base material placed along each edge of the roadway. 
7

HMA base mix 

placed prior to 

paving to widen 

the pavement. 

Note large 

aggregate in 

HMA base mix. 

Figure 5. Surface of the HMA base that had been previously placed to widen the roadway. 

Safety EdgeSM slope. Note coarse, rough 

surface texture and coarse aggregate along 

the surface of the Safety EdgeSM. 

HMA base mix placed prior to paving to 

widen the pavement. Note large aggregate 

in the HMA base mix. 

Close-up of the surface texture of the 9.5 

mm HMA overlay mix of the Safety 

EdgeSM section. 
8

Figure 6. Variable pavement width along the project and shoulder condition. 

Field Evaluation 

Three sections were identified during the paving operation; two Safety EdgeSM sections and 

one section without the Safety EdgeSM device. Field density tests were conducted within 

each test section using a Troxler 3440 nuclear density gauge, while slope measurements were 

taken using a straight-edge and six inch ruler along the two Safety EdgeSM sections. 

Fourteen cores were also taken in the test sections established during the paving operations. 

The fourteen cores were obtained at seven different locations within the Safety EdgeSM and 

non-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. 

The longitudinal profile for determining the International Roughness Index (IRI) was not 

included in the field testing plan for this project for comparing the Safety EdgeSM and nonSafety EdgeSM sections. The Pennsylvania DOT does not measure longitudinal profile for 

calculating the IRI or profile index on these types of rehabilitation projects. 

Two Safety EdgeSM test sections were located, marked and used in the field study, while one 

non-Safety EdgeSM section was included in the field study. During paving, the screed 

operator raised and lowered the Safety EdgeSM device throughout the project. Thus, the 

Safety EdgeSM was not used consistently throughout the project. The reason for periodically 
9

raising the Safety EdgeSM device is provided under the section on Observations for this field 

report. The following summarizes the three test sections included within this field study. 

1. Safety EdgeSM Section #1; southbound lane, just south of the intersection between 

Bellaire Road and Maple Dale Road. The station numbers used in the data sheets 

represent the distance from the intersection of the centerlines for these two roadways. 

This area of the project was selected because it was visually observed that the Safety 

EdgeSM

Non- Safety EdgeSM Control Section; north bound lane on the opposite side of the 

roadway from the Safety EdgeSM Section #1. 

Safety EdgeSM Section #2; northbound lane, north of the intersection between Bellaire 

Road and Maple Dale Road – just north of 365 Bellaire Road. Station 0+35 for this 

section is located at the center of the culvert and PCC drainage pipe (refer to Figure 

7). This section was selected because the Safety EdgeSM device was visually 

observed being used and this area is subject to erosion and future lane-shoulder dropoff. 

shoe/device was being used. 

2.

3.

Figure 7. Reference marker for Safety EdgeSM Section #2. 

Slope Measurements 

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

the taper of the Safety EdgeSM (refer to Figure 8). The average slope of the Safety EdgeSM

was 48°. Table A-1 in Appendix A contains slope measurements recorded at each individual 

measurement location. Only one of the measurements was less than 40°. Figure 9 includes a 

comparison between the slope of the Safety EdgeSM and mat thickness at the Safety EdgeSM

for the two test sections. As shown, there appears to be no correspondence between mat 

thickness and the slope of the Safety EdgeSM.

Area of Safety EdgeSM

Section #2. Station 0+35 

is located at the center of 

the PCC drainage pipe in 

the northbound lane. 
10

A 

B 

Toe of the 

slope 

Break point 

Figure 8. Measurement of the Safety EdgeSM angle.

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

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 significantly steeper than what was planned. 

The slope measurements were found to be variable, because it was difficult to locate the toe 

of the slope of the Safety EdgeSM in areas where some of the 9.5 mm mixture was under the 

screed end plate (refer to Figure 5). The screed operator did try to lower the screed end plate, 

but the end plate pulled dirt and weeds into the mix within the screed extension in some 

areas. 
11

Cores 

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

or location; one in the same area where the densities were measured with the nuclear gauge. 

These cores were taken to measure the bulk specific gravity of the compacted HMA mix for 

developing adjustment factors 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 readings. Nuclear density tests were taken before the cores were drilled. 

Tables A-2 and A-3 in Appendix A include a summary of the core thickness and bulk 

specific gravities (saturated surface dry) converted to bulk densities. Figure 11 shows a 

comparison of the core densities taken along the edge and near the center of the steel drum 

roller for the Safety EdgeSM and non-Safety EdgeSM sections. As expected the densities near 

the center of roller are significantly higher than along the edge of the mat (unconfined edge). 

More importantly, the core densities taken along the pavement’s edge are consistently higher 

for the Safety EdgeSM section than for the non-Safety EdgeSM section. Only one of the cores 

taken along the edge of the Safety EdgeSM section was found to have a lower density than for 

the non-Safety EdgeSM section. These results suggest that the Safety EdgeSM is providing 

better confinement for rolling the unconfined edge of the mat. 

Figure 10. Location of cores and nuclear density tests. 

Core #1; Safety EdgeSM

section (A location is 

adjacent to the Edge; B 

ocation is near the center 

of the steel drum roller 

about 3 feet from edge). 

l

(

Core #2; Non-Safety 

EdgeSM section (A 

location is adjacent to the 

Edge; B location is near 

the center of the steel 

drum roller (about 3 feet 

from edge). 
12

Figure 11. Comparison of core densities adjacent to the edge of pavement and near the 

center of the steel drum roller. 

Nuclear Density Results 

Density measurements were made with a Troxler 3440 gauge. Four readings were recorded 

at each station or location. Two readings were made at a point adjacent to the Safety EdgeSM

and two were made near the center of the steel drum roller. At each point, one reading was 

recorded with the nuclear gauge positioned parallel to the pavement edge and the other 

positioned perpendicular to the edge, which is the Pennsylvania DOT’s standard test 

procedure. The nuclear density gauge readings are listed in Table A-4 in Appendix A. 

Nuclear density readings were taken at each core. Figure 12 shows a comparison of the 

nuclear densities and densities measured on the cores. As shown, there is close 

correspondence between the nuclear and core densities. Adjustment factors were determined 

for the nuclear density readings taken at the Safety EdgeSM and near the center of the steel 

drum roller being used to compact the HMA mat. The adjustment factors are included in 

Table A-3 in Appendix A and are summarized as follows: 

Location Adjustment Factor 

Near Center of Steel Drum 1.000 

Adjacent to Safety EdgeSM 0.980 

As shown, the value near the center of the steel drum roller is unity and the value near the 

Safety EdgeSM is close to unity. These factors were used to adjust the nuclear density gauge 

readings to be consistent with the densities that would be measured in the laboratory. 
13

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

recovered from the HMA overlay. 

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

to the Safety EdgeSM and in the center of the vibratory steel wheel roller. Figure 13 also 

includes a comparison of the HMA air voids between both areas. As shown, the air voids are 

much higher adjacent to the Safety EdgeSM, but are higher than desirable for both areas. The 

other important observation from this data is that the density is higher and the air voids are 

consistently lower for the Safety EdgeSM sections, in comparison to the non-Safety EdgeSM

section. 

Figure 14 compares the HMA mat thickness (near the Safety EdgeSM) and slope of the Safety 

EdgeSM. As shown, the thickness of the HMA mat appears to have no effect or impact on the 

slope of the Safety EdgeSM device.
14

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

areas adjacent to the edge and center of the steel drum roller. 

Nuclear densities 

measured in areas 

adjacent to the edge in 

comparison to those 

taken near the center 

of the steel drum 

roller.

Air voids in areas 

adjacent to the edge in 

comparison to those 

taken near the center 

of the steel drum 

roller. 
15

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

Observations Made During Paving with the Safety EdgeSM

This section overviews some of the observations made during the paving and rolling 

operations. 

Surface Preparation Issues 

A goal of this project was to maximize pavement width. The Safety EdgeSM was added to the 

project after it was designed. The shoulder or edge of pavement was not specifically 

prepared to accommodate the Safety EdgeSM prior to paving. In fact, the Safety EdgeSM was 

placed over grass and other loose materials in some areas of the project. Grass was observed 

at the bottom of one of the cores drilled along the non-Safety EdgeSM section. It is expected 

that the edge will deteriorate rapidly with any traffic loadings in these areas (regardless of 

whether it is a Safety EdgeSM or non-Safety EdgeSM section). Figures 2, 3, and 6 showed the 

edge condition of the pavement after paving. In most areas, grass was adjacent to the edge. 

Figure 15 shows the condition of the existing pavement and the placement of the emulsion 

that was used as a tack coat for the HMA overlay. Figure 16 shows the paving adjacent to 

the shoulder. 
16

Figure 15. An emulsion was used as a tack coat prior to HMA placement (note the material 

that was added to the edge of the pavement to widen the roadway). 

Placement/Paving Operations 

DOT personnel operated the paver in manual mode relative to the longitudinal profile to 

place a 1.5 inch overlay over the existing pavement. The DOT considered this lift as a 

leveling course, thus it was not correcting the longitudinal profile of the surface. Figure 16 

shows the paver in operation, while Figure 17 shows the Safety EdgeSM device attached to 

the screed prior to the paving operation. 

The following summarizes some of the observations and comments made by construction 

personnel on the use of the Safety EdgeSM device. 

 The screed operator’s opinion was that it was difficult to control the height of the 

screed, screed end plate, screed extension, and Safety EdgeSM. It was recommended 

that the Safety EdgeSM device be automated rather than operated by manually turning 

the screw. 

 One major issue that was observed during the paving operation was that the bottom 

part of the Safety EdgeSM device or shoe would periodically get caught on the coarse 

aggregate of the HMA base mix used to widen the roadway. This caused a sudden 

jerk in the screed when the coarse aggregate-broke loose or the Safety EdgeSM 

device/screed rose above the aggregate. The screed operator forced the Safety 
17

EdgeSM device down onto the HMA base in accordance with the manufacturer 

recommendations, which was evident by scratch marks on the surface of the HMA 

base (refer to Figure 18 that shows this condition). It is expected that excessive 

downward pressure exerted on the Safety EdgeSM device could cause the screed to 

rise in areas where the device was in contact with the HMA base. To prevent this 

condition, the screed operator suggested raising the Safety EdgeSM device to a height 

about 0.5 inches above the bottom of the end plate. The screed operator also 

suggested attaching the Safety EdgeSM device to the screed end plate rather than to 

the screed. The screed end plate, however, would need to be significantly stiffened. 

 The other detrimental issue was that the screed end plate ski was riding on the surface 

of the shoulder and in some cases, pulled dirt and weeds into the mix. The screed 

operator felt that the screed end plate ski had to be lowered sufficiently so that the 

mix was being retained by the Safety EdgeSM

The screed and paver operators were concerned about overrunning the quantity of 

HMA estimated for this project because of the additional material being placed along 

the edge (increasing yield). For this reason and dragging the shoulder edge noted 

above, the screed operator tried to keep the Safety EdgeSM and edge of the mat on the 

HMA base. 

shoe. 



 There were localized areas along the northern portion of the project where the slope 

of the shoulder was steeper than 30° for an extended distance past the pavement’s 

edge. In these areas, the screed operator did not extend the screed out, but raised the 

Safety EdgeSM device and lowered the screed end plate ski to create a non-Safety 

EdgeSM. This is what the screed operator should do under these conditions. One of 

these areas is shown in Figure 19. 

 The Safety EdgeSM device was able to move in some areas when the paver was 

placing the HMA mixture near the intersections and driveways; when the screed was 

extended further out from the mainline paving (refer to Figure 20). Once a sufficient 

amount of mixture was pushed out to the screed end plate, the Safety EdgeSM device 

remained in close contact with the screed and screed end plate. 
18

Figure 16. Photo illustrating the edge condition of the pavement. 
19

Safety EdgeSM device 

attached to screed and 

in place at the 

beginning of the 

paving. 

Beginning of day’s 

construction; transverse 

joint created prior to 

paving. 

Point of Safety EdgeSM device that periodically hung on the larger aggregate of 

the HMA base mix placed prior to paving operations (see Figure 5). 

Figure 17. Safety EdgeSM device attached to the screed. 
20

Mark on HMA base material left by the Safety EdgeSM device with 

pressure applied in an attempt to increase the slope. 

Mark on HMA base material left by the 

Safety EdgeSM device with pressure applied 

in an attempt to increase the slope. 

Figure 18. Gouges in the HMA left by the Safety EdgeSM device riding on the surface of 

HMA base mix.
21

L

ar

th

th

w

th

of

E

e

di

th

e

Figure 19. Area where the slope of the shoulder was steeper than the Safety EdgeSM slope. 

ocalized 

ea where 

e slope of 

e shoulder 

as steeper 

an the slope 

 the Safety 

dgeSM for an 

xtended 

stance past 

e roadway’s 

dge. 
22

Figure 20. Photographs showing where a sufficient and insufficient amount of head of HMA 

was retained in the extended auger chamber area. 

Localized area where 

the screed was 

extended to place the 

overlay at 

intersections and an 

insufficient amount of 

material was retained 

in the extension area 

to restrain movement 

of the Safety EdgeSM

device. 

During mainline 

paving, sufficient 

amount or head of 

material was retained 

in the extension area 

so that Safety EdgeSM

device was restrained 

and could not move. 

Compaction Operations 

Figure 21 shows the two rollers that were used to compact the HMA 9.5 mm mixture. The 

breakdown roller was a Dynapac CC422VHF and the finish roller was an Ingersoll-Rand 

DD90. 
23

Figure 21. Two steel wheel rollers used to compact the 9.5 mm HMA mix. 

Vibratory steel wheel roller used in the breakdown position for 

compacting the 9.5 mm HMA overlay mix. 

Steel wheel roller used in the finish position for compacting the 

9.5 mm HMA mixture (operated in the static mode). 

The Dynapac steel wheel roller was operated in the high frequency, low amplitude vibratory 

mode, while the Ingersoll-Rand roller was operated in the static mode. The breakdown roller 

was operated close behind the paver. The finish roller was operated right behind the 
24

breakdown roller along most of the areas. The following summarizes the number of passes 

and coverage used by both rollers. 

 Dynapac steel wheel roller; high frequency, low amplitude; primary or breakdown 

roller: 

o First pass along and extended over the shoulder edge by about 2 to 6 inches 

with vibration. 

o Second pass; same location as for first pass but in reverse without vibration. 

o Third pass along the center of the mat in low amplitude with vibration. 

Fourth pass along the centerline with the edge of the drum extended over the 

edge about 2 to 6 inches with vibration. 

o

o Fifth pass same as location for the fourth pass but without vibration. 

 Ingersoll-Rand steel wheel roller; static mode; finish roller: 

o First pass along the shoulder edge with the edge of the steel wheel roller 

extended over the edge about 2 to 6 inches. 

o Second pass; same location as for the first pass. 

o Third pass down the center of the mat. 

o Fourth pass along the center of the roadway with the edge of the steel drum 

extended over the edge by about 2 to 6 inches. 

o Fifth pass; same location as for the fourth pass. 

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

adequate density of the mix. The nuclear density readings and the densities of the cores 

found that an insufficient density level was obtained for this mixture. 

One possible explanation for this low density is that the breakdown roller was being operated 

in the low amplitude and the thickness of the mat was less than 1.5 inches in many areas of 

the project. HMA lifts less than 1.5 inches in thickness may need to be compacted using the 

static mode of a steel wheel roller. 

No visual signs of shoving or tearing of the mixture were noted or observed during the 

compaction operation. In addition, the Safety EdgeSM slope did not shove out or become 

more vertical, during the compaction operation. In a couple areas of the project, the mixture 

was easily depressed after compaction. It is expected that the supporting layers are soft. In 

addition, only localized areas exhibited broken aggregate under the vibratory rollers and most 

of these areas were along the confined longitudinal joint – on the cold side of the joint. 

The Safety EdgeSM was rolled inconsistently during the project. The majority of the rolling 

pattern, however, was that the first pass of the breakdown roller was along the Safety EdgeSM

with the roller extended over the edge of the pavement by about 4 to 6 inches (refer to Figure 

22). 
25

Figure 22. Vibratory steel wheel roller used in the breakdown position shown compacting 

the Safety EdgeSM – first pass overhung the edge about 4 inches. 

HMA Mixture Characteristics and the Safety EdgeSM

The HMA mixture design data was obtained from the Pennsylvania DOT. The HMA 

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

document to this field report. 

Observations made during paving showed that the HMA mixture was not being pushed to the 

end of the Safety EdgeSM device. Figure 23 shows HMA behind the screed and the Safety 

EdgeSM slope prior to rolling. The slope of the Safety EdgeSM was steeper than planned prior 

to rolling because the mix was not being pushed to the end of the Safety EdgeSM. The 

specific reason for the HMA not being pushed to the end of the Safety EdgeSM device is 

unknown for this project. The only mixture design parameter that might have an impact on 

the slope of the Safety EdgeSM and surface texture, however, was voids in the mineral 

aggregate (VMA). The design VMA was reported to be 17.4 and is considered high for this 

HMA mixture. It is unknown whether the higher VMA resulted in the steeper slopes 

measured along this project. 
26

Figure 23. HMA shown under and behind the screed; the HMA was not pushed to the end of 

the Safety EdgeSM resulting in a steeper slope prior to rolling. 

Note: HMA under the 

screed end plate ski. The 

slope of the Safety EdgeSM

was steeper than 30°, even

prior to rolling. Slope 

measurements prior to 

rolling, however, were not 

made on this project. 

Note: HMA behind the 

screed. HMA was not being 

pushed to the end of the 

Safety EdgeSM, so the Safety 

EdgeSM slope prior to rolling 

was steeper than 30°. 

Note: HMA for the Safety 

EdgeSM being placed over 

grass. 

It was also observed that the HMA mixture was not moving above the Safety EdgeSM device 

– near the screed end plate assembly. HMA mixture was observed to be stationary above the 

Safety EdgeSM device. The distance between the end of the auger and screed end plate was 

about 18 to 24 inches. This distance should be less than 18 inches. The reason for the 

mixture bridging at the surface and not being transferred under the screed is unknown. 

However, this may also explain the HMA mix not being pushed to the end or edge of the 

Safety EdgeSM device. The temperature of the HMA being delivered to the project site was 

reported to be 313 to 327 °F, so it is expected that the temperature of the mix was not a factor 

for the mix being held in the corner of the screed extension. 
27

Findings and Conclusions 

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

HMA material and Safety EdgeSM by investigating three features. 

1. Correct use of the 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 some of the findings and conclusions made 

during the paving/compaction operations.

 

 This project is considered an anomaly because of the edge condition along many 

sections of the roadway. The purpose of this project was to maximize the roadway 

width, which caused the Safety EdgeSM to be placed over loose soil and grass in some 

areas of the project. The project was not designed with the concept of using the 

Safety EdgeSM. In addition, the Safety EdgeSM device was used randomly along the 

project. Those areas included in this field study were observed during paving to 

ensure that the Safety EdgeSM was being used. For the other areas, it is unknown 

whether the Safety Edge was used or was raised during paving. SM

 Although the 9.5 mm HMA mixture is considered a relatively fine aggregate mixture, 

the surface texture of the mixture and along the Safety EdgeSM was coarse. More 

importantly, the coarse aggregate were loose along the bottom of the Safety EdgeSM

and could be easily removed. As noted in the field report, this could be one of the 

reasons why the width of the Safety EdgeSM was so narrow – resulting in a much 

steeper slope than expected. 

 The density of the HMA mixture adjacent to the Safety EdgeSM was found to be 

higher than along the unconfined edge in the areas placed without the Safety EdgeSM

– a positive benefit from the Safety EdgeSM device. 

 Many areas along this project were excluded from the field study because the 

thickness of the HMA lift was less than 1.5 inches. The thicknesses, densities, and 

slopes are only representative of those areas where the HMA thickness near the edge 

of the pavement was near or greater than 1.5 inches. 

The pavement should be inspected after the final shoulders have been constructed. Millings 

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

to observe the millings placement and ensure that meets proper relative elevation to the HMA 

mat. Long term monitoring of the shoulder should be performed to see how well the millings 

shoulder remains in place and observe any deformation or erosion in the shoulder. 
A-1 

APPENDIX A. DATA TABLES FROM FIELD MEASUREMENTS 

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 demonstration projects. 

Table A-1. Safety EdgeSM slope measurements. 

Table A-2. Core thickness measurements. 

Width of Taper Thickness of 

Taper

Slope

1 984.8 1.25 1.25 45

1 934.8 1.5 1.875 51

1 884.8 2.5 2.375 44

1 834.8 1.5 1.75 49

3 747 1 1.5 56

3 697 1.625 2.25 54

3 647 1.625 1.375 40

3 597 1.75 2 49

3 547 1 1.25 51

No core 0+00 2.875 2.25 38

No core 0+25 1.5 2 53

No core 0+50 1.5 1.75 49

No core 1+00 1.5 2.125 55

No core 1+25 1.5 1.5 45

No core 1+50 1.5 1.375 43

No core 1+75 2.25 2.125 43

Mean Value 1.648 1.797 47.813

Standard Deviation 0.500 0.382 5.431

Coefficient of Variation, % 30.4 21.2 11.4

Core/Section ID Station

Safety Edge

0+35 for this section is at the culvert and center of the PCC 

pipe (identified by a delineator). This section is north of the 

intersection with Maple Dale Road in the northbound lane 

and south of 365 Bellaire Road. This section looked the 

best.

Section Identifier

Location relative to the cores taken and to the intersection

between Bellaire Road and Maple Dale Road.

A – Adjacent to 

Edge

B – 3 feet 

from Edge

1 Southbound 884.8 Safety Edge 1.25 1.5

2 Northbound 886.4 Non Safety Edge 1.5 1.75

3 Southbound 597 Safety Edge 1.25 1.5

4 Southbound 515 Non Safety Edge 1.5 1.5

5 Southbound 429.6 Non Safety Edge 1 1.25

6 Southbound 1125 Non Safety Edge 1.75 1.75

7 Southbound 782.5 Safety Edge

2 2

1.464 1.607

0.336 0.244

22.97 15.18

Station Type of Section Core Thickness, in.

Area/Location Core #

Areas south of intersection 

between Bellaire Road and 

Maple Dale Road

Lane Direction

Mean, in.

Standard Deviation, in.

Coefficient of Variation, %

Areas north of intersection 

between Bellaire Road and 

Maple Dale Road
A-2 

Table A-3. Nuclear density adjustment factors; core density/nuclear density. 

Table A-4. Density readings made with a nuclear density gauge (Troxlor gauge 3440). 

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

1 Southbound 884.8 Safety Edge 128.2 139.0 139.75 139.75 0.917 0.995

2 Northbound 886.4 Non Safety Edge 129.8 139.7 128.85 139.00 1.007 1.005

3 Southbound 597 Safety Edge 135.7 135.0 138.60 137.15 0.979 0.984

4 Southbound 515 Non Safety Edge 131.4 141.4 136.65 146.60 0.962 0.965

5 Southbound 429.6 Non Safety Edge 133.4 139.0 134.55 137.90 0.991 1.008

6 Southbound 1125 Non Safety Edge 133.8 143.2 132.90 138.50 1.007 1.034

7 Southbound 782.5 Safety Edge 140.3 142.8 140.45 141.85 0.999 1.007

133.23 140.01 135.96 140.11 0.980 1.000

4.0178 2.8026 4.1608 3.2339 0.0322 0.0217

3.02 2.00 3.06 2.31 3.28 2.17

Adjustment Ratio

Core # Lane Direction Station Type of Section

Density of Cores Nuclear Density Values

Areas south of intersection 

between Bellaire Road and 

Maple Dale Road

Areas north of intersection 

between Bellaire Road and 

Maple Dale Road

Area/Location

Mean Value, pcf

Standard Deviation, pcf

Coefficient of Variation, %

Summary Values

2.543 Max. Density: 158.7

A= 0.980

B= 1.000

A – Adjacent to 

Edge

B – 3 feet from 

Edge

A – Adjacent to 

Edge

B – 3 feet 

from Edge

1 Southbound 984.8 Safety Edge 1.25

1 Southbound 934.8 Safety Edge 139.60 145.75 136.81 145.75 1.875 13.79 8.16

1 Southbound 884.8 Safety Edge 139.75 139.75 136.96 139.75 2.375 13.70 11.94

1 Southbound 834.8 Safety Edge 139.40 141.45 136.61 141.45 1.75 13.92 10.87

3 Southbound 747 Safety Edge 1.5

3 Southbound 697 Safety Edge 2.25

3 Southbound 647 Safety Edge 137.35 135.60 134.60 135.60 1.375 15.18 14.56

3 Southbound 597 Safety Edge 138.60 137.15 135.83 137.15 2 14.41 13.58

3 Southbound 547 Safety Edge 141.90 140.90 139.06 140.90 1.25 12.37 11.22

7 Southbound 712.5 Safety Edge 138.30 136.05 135.53 136.05 14.60 14.27

7 Southbound 782.5 Safety Edge 140.45 141.85 137.64 141.85 13.27 10.62

7 Southbound 812.5 Safety Edge 143.55 143.40 140.68 143.40 11.36 9.64

139.878 140.211 137.080 140.211 1.736 13.623 11.650

1.895 3.422 1.857 3.422 0.421 1.170 2.157

1.35 2.44 1.35 2.44 24.27 8.59 18.51

2 Northbound 986.4 Non-Safety Edge

2 Northbound 936.4 Non-Safety Edge 136.65 139.25 133.92 139.25 15.62 12.26

2 Northbound 886.4 Non-Safety Edge 128.85 139.00 126.27 139.00 20.43 12.41

2 Northbound 836.4 Non-Safety Edge

4 Southbound 515 Non-Safety Edge 136.65 146.60 133.92 146.60 1.625 15.62 7.62

4 Southbound 465 Non-Safety Edge 138.45 147.80 135.68 147.80 1.75 14.50 6.87

5 Southbound 429.6 Non-Safety Edge 134.55 139.45 131.86 139.45 1.75 16.91 12.13

5 Southbound 379.6 Non-Safety Edge 136.50 137.90 133.77 137.90 2.25 15.71 13.11

5 Southbound 329.6 Non-Safety Edge 1.5

6 Southbound 1075 Non-Safety Edge 132.25 136.05 129.61 136.05 18.33 14.27

6 Southbound 1125 Non-Safety Edge 132.90 138.50 130.24 138.50 17.93 12.73

6 Southbound 1175 Non-Safety Edge 134.75 141.05 132.06 141.05 16.79 11.12

134.617 140.622 131.924 140.622 1.775 16.872 11.391

2.923 3.971 2.864 3.971 0.285043856 1.805 2.502

2.17 2.82 2.17 2.82 16.0588088 10.70 21.97

Standard Deviation

Core 

Location

Lane Direction

Average Value

Adjusted N

A – Adjacent 

to Edge

uclear Values

B – 3 feet 

from Edge

Standard Deviation

Air Voids, %

HMA 

Location/Area Thickness, in.

Areas south of intersection 

between Bellaire Road and Maple Dale Road

Areas north of intersection 

between Bellaire Road and Maple Dale Road

Coefficient of Variation

Maximum Specific Gravity of Mix:

Adjustment Ratios for Nuclear 

Gauge:

Average Value

Areas north of intersection 

between Bellaire Road and Maple Dale Road

Station Type of Section Nuclear Densities

Areas south of intersection 

between Bellaire Road and Maple Dale Road

Coefficient of Variation