Safety Edge SM

Demonstration Project 

State Route 182 

Columbus, Mississippi 

Field Report 

June 27, 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 on State Route (SR) 182 near Columbus, 

Mississippi. 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. 

This report is a summary of the observations made on July 12 through 15, 2010 and 

measurements taken during construction to evaluate the use of the TransTech Shoulder 

Wedge Maker. Observations and data were collected to evaluate the slope and density of the 

Safety EdgeSM, recommend design adjustments, and identify benefits and complications with 

the use of the edge device. 
1. Report No. 2. Government Accession No 3. Recipient’s Catalog No

3. Title and Subtitle 

Safety EdgeSM Demonstration Project, 

State Route 182 near Columbus, Mississippi 

5. Report Date 

 June 27, 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 

 April – June 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 the Safety EdgeSM on a two lane highway hot mix 

asphalt (HMA) overlay project on State Route 182 near Columbus, Mississippi. The TransTech Shoulder Wedge Maker 

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, TransTech Shoulder 

Wedge Maker 

18. Distribution Statement 

No restriction. 

19. Security Classif.(of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

29

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 

Topic Page 

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

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

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

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

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

Compaction ............................................................................................................................. 1

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

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

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

INTRODUCTION ............................................................................................................................... 3

PAVEMENT STRUCTURE AND PROJECT CONDITIONS .................................................................... 4

FIELD EVALUATION TESTS ............................................................................................................ 7

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

Cores ..................................................................................................................................... 10

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

Longitudinal Profile Measurements ..................................................................................... 13

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

Preparatory Work ................................................................................................................. 15

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

Compaction Operations ........................................................................................................ 20

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

Other Observations Related to Site Features ....................................................................... 27

FINDINGS AND CONCLUSIONS ...................................................................................................... 28

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 device 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. These are noted in some of the following bullet items. 

Slope of Safety EdgeSM

 The average slope of the Safety EdgeSM was found to be 37°. Only one slope 

measurement was found to be near 30°. 

 Slope measurements of the Safety EdgeSM were taken before and after rolling in separate 

areas of the project. The slopes before and after rolling were found to be approximately 

equal (an average slope of 37.0 degrees after rolling compared to an average slope of 

40.1 degrees prior to rolling). Rolling did not steepen the slope of the Safety EdgeSM

along this project. 

Placement 

 The Safety EdgeSM was formed using the TransTech Shoulder Wedge Maker, which was 

properly bolted to the screed. Construction personnel recommended that the Safety 

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

 The Safety EdgeSM shaft or screw for raising and lowering the device had been bent from 

use on a previous project. Excessive downward pressure from trying to lower the device 

on a hard surface caused the shaft to bend. The bend caused the device to rotate when the 

screed operator tried to raise or lower the device – allowing HMA mix to get between the 

screed end plate and Safety EdgeSM device. HMA mix getting between the device and 

screed end plate varied along the project. This could have resulted in a steeper slope 

along the project. 

Compaction 

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

for the Safety EdgeSM sections (average air voids of 10.6 percent) in comparison to the 

non-Safety EdgeSM section (average air voids of 12.3 percent). Thus, the Safety EdgeSM

is believed to have a confining effect on rolling an unconfined edge condition. This 

observation is considered a benefit to the use of the Safety Edge . SM

 The air voids of the interior HMA mat were considered good with a mean value of about 

6.5 percent for both the safety and non-Safety EdgeSM sections. The air voids determined 
2

along the edge of the mat were high (varying from 9 to almost 15 percent). This air void 

content is higher than desirable for long term performance. 

Shoulder Construction 

 A soil-aggregate mixture is planned to be used for the backing material. Placement of the 

backing material was not observed because the paving contractor planned to place it after 

all paving had been completed. 

HMA Mixture and Safety EdgeSM

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

 The planned HMA overlay thickness was 1.5 inches. The average overlay thickness of 

the Safety EdgeSM sections was found to be 2.0 inches, while the average thickness of the 

non-Safety EdgeSM section was found to be 2.75 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. 
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 the HMA 

overlay placed along State Route 182 just east of Columbus, Mississippi, with and without 

the use of the Safety EdgeSM device. The paving contractor for the project was Falcon 

Construction. The contractor used the TransTech Shoulder Wedge Maker along most of the 

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

Plymouth Road and ended at the Alabama State line. The western end of the project, through 

the downtown area, was excluded from the Safety EdgeSM project because of curb and gutter 

within the City Limits and numerous driveways. The portion of the project for the Safety 

EdgeSM started at the intersection with South Lehmberg Road and proceeded east to the 

Alabama State Line (refer to Figure 1). 

Figure 1. Project location. 

Safety EdgeSM Portion of Project Started 

at intersection with S. Lehmberg Rd. 

Safety EdgeSM Portion of Project ended 

at the Alabama State Line. 
4

Pavement Structure and Project Conditions 

The project consisted of milling the existing surface to a depth of about 1.5 inches (basically 

removing the existing wearing surface) and placing a 1.5 inch lift of a 9.5 mm HMA mix 

over the existing HMA pavement. Figure 2 provides a general view of the 1.5 inch HMA 

overlay and typical cross section of the pavement, while Figures 3 and 4 provide a general 

view on the condition of the existing pavement after milling. These figures show that a thin 

layer or scab of the existing wearing surface was left in place. This thin layer may become 

debonded with time and have a detrimental impact on the performance of the HMA overlay. 

A leveling course was placed in some areas along the project, and the existing pavement was 

widened to include two 12-foot lanes and a 2-foot width for the edge stripe and rumble strip 

planned to be placed on both sides of the roadway. The leveling course was placed along 

localized areas of the project to improve the transverse and longitudinal profiles (refer to 

Figure 2). The existing shoulder was trenched 2 feet wide, and a 19 mm HMA base mixture 

was placed with a motor-grader and compacted in the trench. The 19 mm HMA base was 

used to widen the roadway by 2-feet on each side and had been placed prior to arriving on 

site. Figure 5 shows the HMA base to widen the roadway, and the windrow of shoulder 

material from the trenching operation. 

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

pavement (refer to Figures 3 to 5). No lane-shoulder drop-offs were observed. As noted 

above, however, the edge of the pavement had been trenched and the HMA base mix had 

already been placed to widen the roadway by 2-feet on each side. The Safety EdgeSM

backing material is the trenched soil-aggregate mixture. The backing material was scheduled 

to be graded back to the Safety EdgeSM near the end of this rehabilitation project. 
5

Figure 2. 9.5 mm HMA overlay already placed in one direction and the thin leveling layer 

placed in opposite direction after milling but prior to overlay placement. 

9.5 HMA Overlay, 1.5 inches 

planned thickness; roadway 

width over bridge is 22 feet. 

Thin HMA leveling course 

placed in selected areas along 

the roadway, after milling. 

24-Foot Roadway Width 

Planned 1.5 inch HMA 9.5 mm Overlay 

Existing HMA Pavement; Surface Milled 1.5 inches 

Prior to Overlay 

Existing shoulder trenched 2-foot wide to place 6 inches of 19 

mm HMA base for widening both sides of roadway for placing 

rumble strip and an edge strip on both sides of roadway. 
6

Figure 3. General overview of the existing HMA pavement after milling; heavily distressed 

area with cracking (view is towards the east). 

Scab of existing 

wearing surface 

left in place after 

milling operation. 

Figure 4. General overview of the existing HMA pavement after milling; minor distressed 

area (view is towards the east). 

Windrow of 

trenched 

shoulder 

material. 

1.5 to 2.0 inch 

9.5 mm HMA 

overlay. 

HMA base mix 

placed in 

trenched 

shoulder 

material. 

Scab of existing 

wearing surface 

left In place 

after milling 

operation. 
7

Figure 5. General view of the 19 mm HMA base placed to widen the roadway. 

Windrowed material 

from the 2-foot wide 

trench. 

19 mm HMA base 

mix placed in the 

trenched area to 

widen the roadway. 

Field Evaluation Tests 

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

sections and one section without the Safety EdgeSM device. The following summarizes the 

three sections included within this project. 

1. Area #1: Non-Safety EdgeSM control section located in the eastbound lane from 

station 397+00 to station 408+00. 

2. Area #2: Safety EdgeSM section located in the eastbound lane from station 429+00 to 

station 435+00. 

3. Area #3: Safety EdgeSM section located in the eastbound lane from station 439+00 to 

station 445+00. 

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

Slope measurements were taken using a straight-edge (4-foot aluminum level) and six inch 

ruler (refer to Figure 6), while density readings were taken adjacent to and 3-feet from the 

mat’s edge using a Troxler 3440 nuclear density gauge (refer to Figure 7). 

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

sixteen cores were obtained at eight different locations (4 within the Safety EdgeSM and 4 

within the 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. 
8

The longitudinal profile was measured by the paving contractor after each day of paving 

using a California Profilometer for determining the smoothness of the 9.5 mm overlay. 

Figure 6. Measurement of the Safety EdgeSM angle.

Break point 

Toe of 

the slope 

A 

B 

Figure 7. Nuclear gauge used to measure HMA density. 
9

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 6). The average slope of the Safety EdgeSM

was found to be 37°. All slope measurements are listed in Tables A-1 through A-3 in 

Appendix A. Only one of the measurements was about 30°. Figure 8 includes a comparison 

between the slope of the Safety EdgeSM after final rolling and thickness of the Safety EdgeSM

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

thickness and the slope of the Safety EdgeSM.

Slope measurements were also made prior to rolling the Safety EdgeSM. These 

measurements are in Table A-2 in Appendix A and were compared to the values after final 

rolling; refer to Figure 8. As shown, the slopes prior to rolling are slightly steeper than after 

final rolling. These data sets were measured in different areas, so there is no direct 

correspondence between the individual point measurements. An observation from this 

comparison is that rolling did not steepen the slope, and suggests that rolling the Safety 

EdgeSM by overhanging the steel drum about 4 to 6 inches over the edge did not increase the 

slope. The rolling patterns used along the project are explained in the Compaction 

Operations section. 

Slopes were also measured along the non-Safety EdgeSM section. These slope measurements 

are included in Table A-3 in Appendix A and shown in Figure 8. As expected, the slopes 

without use of the Safety EdgeSM are greater than when using the Safety EdgeSM device. 

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. 

Figure 8. Comparison of the Safety EdgeSM slope and thickness of the HMA adjacent to the 

edge of the HMA overlay. 
10

Cores 

A total of sixteen 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 HMA for 

developing a correction factor for the nuclear density gauge readings taken adjacent to the 

edge and within the center of the mat. Figure 9 shows the location of the cores and nuclear 

density readings relative to the edge of the HMA mat. Photographs of each core recovered 

from the roadway are included in Appendix A. 

Tables A-4 and A-5 in Appendix A include a summary of these test results; core thickness 

and bulk specific gravities (saturated surface dry) converted to bulk densities. Figure 10 

includes 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, 

densities near the center of roller are 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. These results suggest 

that the Safety EdgeSM is providing better confinement for rolling an unconfined edge of the 

mat. 
11

Figure 9. Photos showing location of cores and nuclear density tests made with the Troxler 

3440 gauge (nuclear density readings were taken and then the HMA overlay was cored). 

Location of nuclear 

density test; A location is 

adjacent to the edge; B 

location is near the center 

of the steel drum roller 

(about 3 feet from edge). 

Core sets recovered from 

selected stations; 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 10. Comparison of core densities adjacent to the edge of pavement and near center of 

steel drum rollers.

Nuclear Density Test Results 

Density measurements were made with a Troxler 3440 gauge (refer to Figure 7). 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. A

each point, one reading was recorded with the nuclear gauge positioned parallel to the 

pavement edge and the other positioned perpendicular to the edge. The average nuclear 

density gauge readings at each point are listed in Table A-5 in Appendix A. 

Nuclear density readings were taken before drilling each core. Figure 11 shows a 

comparison of the nuclear gauge readings and densities measured on the cores. As shown, 

there is close correspondence between the nuclear gauge readings and core densities. 

Adjustment factors were determined for the nuclear gauge 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-4 in Appendix A. The following lists the 

average factors determined for this project, which are near unity. 

t 

Location Adjustment Factor 

Near center of steel drum 1.007

Adjacent to Safety EdgeSM 1.005

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

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

correction factors are listed in Table A-4 in Appendix A. 
13

Figure 11. Comparison of the nuclear density readings and densities measured on the cores 

recovered from the mat. 

Figure 12 shows a comparison of the adjusted nuclear density gauge readings taken adjacent 

to the Safety EdgeSM and near the center of the vibratory steel wheel roller. Figure 12 also 

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

higher adjacent to the Safety EdgeSM, in comparison to 3-feet from the Safety EdgeSM. The 

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

consistently lower along the mat’s edge for the Safety EdgeSM sections, in comparison to the 

non-Safety EdgeSM section. 

Figure 8 included a comparison between the HMA thickness (near the Safety EdgeSM) and 

slope of the Safety EdgeSM. The thickness of the HMA appears to have no effect or impact 

on the slope of the Safety EdgeSM. Figure 13 shows a comparison of the density and HMA 

overlay thickness. As shown, there is also little correspondence between the overlay 

thickness and density or air voids. 

Longitudinal Profile Measurements 

The longitudinal profile measurements made by Falcon Construction using the California 

Profilometer for each of the three test sections were requested, but were unavailable at the 

time of this field report. The purpose of these measurements were to compare the smoothness 

of the Safety EdgeSM and non-Safety EdgeSM sections to ensure that the Safety EdgeSM device 

was not having a detrimental impact on the contractor’s ability to meet the smoothness 

specification. 
14

Figure 12. 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 13. Comparison of HMA thickness at the edge of the mat and HMA air voids. 

Observations Made During Paving with the Safety EdgeSM

This section provides an overview of the observations made during the paving and rolling 

operations. 

Preparatory Work 

Figures 3 and 4 showed examples of the existing pavement after milling but prior to HMA 

overlay placement. The trenched material that was removed to widen the roadway was 

windrowed. As previously discussed, the scab of the existing wearing surface that was left in 

place in some areas after milling could become debonded in the future and have a detrimental 

impact on the performance of the HMA overlay; regardless of whether it is a Safety EdgeSM

or non-Safety EdgeSM section. The following lists the different activities performed by the 

contractor in placing the HMA overlay. 

1. The edge of the pavement or shoulder was graded to level out the windrowed 

material, as shown in Figure 14. The edge of this windrowed material was not 

compacted prior to placing the Safety EdgeSM. In some areas, this material was loose. 

2. The motor grader was followed by a broom to clean the surface, as shown in Figure 

14. Cleaning the surface is considered good practice prior to placing the tack coat. 

3. An emulsion was applied to serve as a tack coat for the HMA overlay. Figure 14 

shows the emulsion being placed prior to paving. The application of the tack coat 

was uniform and covered the entire surface. 
16

Figure 14. Surface preparation activities performed by the contractor prior to placing the 

HMA overlay. 

Motor grader was used to 

move and level the windrowed 

material along the edge of the 

pavement. In a few areas, the 

motor grader was used after 

the tack coat had already been 

applied. 

A motorized broom was used 

to clean the surface of the 

pavement prior to applying the 

tack coat to the surface of the 

existing pavement. 

A tack coat (emulsion) was 

applied to the cleaned 

pavement surface prior to 

placing the HMA overlay. 
17

Placement/Paving Operations 

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

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

sonic sensors for controlling the grade. Figure 16 shows the TransTech Shoulder Wedge 

Maker attached to the screed. The following summarizes some of the observations and 

comments made by construction and other on-site personnel on the use of the Safety EdgeSM

device. 

 The screed operator recommended that the Safety EdgeSM device be an automated 

system rather than manually turning the screw to raise and lower the Safety EdgeSM

device. 

 The shaft of the Safety EdgeSM device was bent during use on a previous project, such 

that when the screed operator turned the screw to raise or lower the device, the device 

would rotate creating a space between the end plate and Safety EdgeSM device. HMA 

material could then become lodged between the screed end plate and the Safety 

EdgeSM device. The screed operator continued to monitor this condition to prevent it 

from occurring, but in some cases HMA mix would push the device away from the 

screed end plate – increasing the slope. This condition may have resulted in some of 

the steeper slopes that were measured within the Safety EdgeSM Area #3 (refer to 

Table A-1 in Appendix A). 

Figure 17 shows the slope and surface texture of the unconfined edge between the Safety 

EdgeSM and non-Safety EdgeSM sections. 

Figure 15. Equipment used to place the HMA overlay. 
18

Figure 16. TransTech Shoulder Wedge Maker attached to the screed. 

TransTech Shoulder Wedge 

Maker used on the project. 

The bottom part of the shaft 

or screw was bent from use 

on a previous project. When 

the screed operator tried to 

turn the device, it would 

rotate from the screed end 

plate, allowing HMA to get 

between the device and 

screed end plate. 

Note the gap between the Safety 

EdgeSM device and screed end plate.
19

Figure 17. Safety EdgeSM and non-Safety EdgeSM sections; different days of paving. 

Safety EdgeSM section non-Safety EdgeSM section 

Safety EdgeSM

Section. 

Non-Safety EdgeSM

Section. 
20

Compaction Operations 

Figures 18 and 19 show the rollers that were used to compact the 9.5 mm HMA mixture. 

Two breakdown rollers were used in parallel for most of the project (refer to Figure 18). One 

of the primary or breakdown rollers was a Sakai double drum vibratory steel wheel (SW990), 

and the other breakdown roller was a Hypac double drum vibratory steel wheel (C778B). 

Both rollers were operated in the vibratory mode (low amplitude, high frequency). The third 

roller used on the project was an Ingram pneumatic, rubber tired roller (5x6 tires) and used in 

the intermediate position (refer to Figure 19). The finish roller was a Hypac static steel wheel 

roller (C784 [refer to Figure 19]). 

Figure 18. Two double drum vibratory steel wheel rollers were used in parallel in the 

breakdown position to compact the 9.5 mm HMA mix. 

Initial Rolling 

Pattern: first two 

passes of the Sakai 

roller were away 

from the safety edge, 

and the final pass was

along the Safety 

EdgeSM. 

Note the location of 

the roller’s edge for 

the first two passes. 

This may result in a 

longitudinal crack 

with time where the 

first two passes were

along the same line. 

Revised Roller 

Pattern: first pass 

of Sakai roller 

over the Safety 

EdgeSM. 

Sakai Double Drum Vibratory SW990 Hypac Double Drum Vibratory C778B 
21

Figure 19. Rollers used in the intermediate and finish positions for compacting the 9.5 mm 

HMA overlay mixture. 

Ingram pneumatic 

or rubber tired 

roller (5x6 tires) 

that was used in 

the intermediate 

position. 

Hypac Double 

Drum static steel 

wheel (C784) 

that was used in 

the finish 

position for 

compacting the 

HMA overlay. 

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. The contractor used two rolling patterns 

along the project. The following summarizes the initial rolling pattern (number of passes and 

location for each roller) used by the Contractor. 

 Hypac double drum steel wheel roller; high frequency, low amplitude; primary or 

breakdown roller (the lead roller in most areas): 
22

o First pass along the centerline of the roadway with the edge of the drum 

extended over the hot mat about 2 to 6 inches. 

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

o Third pass down the center of the hot mat. 

 Sakai double drum steel wheel roller; high frequency, low amplitude; primary or 

breakdown roller, in parallel with the Hypac roller: 

o First pass near the Safety EdgeSM, but with the edge of the drum about 6 to 12 

inches from the Safety EdgeSM on the interior of the mat (refer to Figures 18 

and 20.b). 

o Second pass; down the center of the mat. 

o Third pass along the Safety EdgeSM with the edge of the drum adjacent to or 

just over the Safety EdgeSM

Ingram Pneumatic rubber tired roller; intermediate roller: 

. 



o First pass along the Safety EdgeSM with the outer tire located a couple of 

inches from the edge of the mat. 

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

o Third pass along the centerline with the outer tire located on the hot mat. 

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

o Fifth pass down the center of the mat. 

 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 4 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, but in reverse direction. 

Prior to designating the locations for the Safety EdgeSM test sections, the HMA mix at the top 

of the Safety EdgeSM was being pushed out under the third pass of the Sakai roller, 

steepening the slope of the Safety EdgeSM. The Contractor was asked to revise the rolling 

pattern to observe mixture behavior along the Safety EdgeSM. The major revision was to roll 

the Safety EdgeSM first and extend the edge of the Sakai roller over the Safety EdgeSM. The 

Contractor complied with that request, and the HMA mix did not push out as much. The 

following summarizes the revised rolling pattern (number of passes and location of each 

roller) used by the Contractor in an attempt to reduce or lower the slope of the Safety 

EdgeSM.
Figure 20. Rolling the unconfined edge with the vibratory steel wheel roller; pattern varied 

along the project. 

23

(a) First pass of Sakai roller is 4 to 6 inches over the edge of the mat. 

(b) First pass of Sakai roller is about 6 to 12 inches away from edge of the mat. 

Note the location of the roller’s 

edge for the first pass. This may 

result in a longitudinal crack 

with time where the first two 

passes were along the same line. 
24

 Hypac double drum steel wheel roller; high frequency, low amplitude; primary or 

breakdown roller (the led roller in most areas); rolling pattern remained the same as 

described above. 

 Sakai double drum 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 

(refer to Figure 18 and 20.a). 

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

o Third pass along the center of the mat. 

 Ingram Pneumatic rubber tired roller, intermediate roller; rolling pattern remained the 

same as described above. 

 Ingersoll-Rand steel wheel roller, static mode, finish roller; rolling pattern remained 

the same as described above. 

This rolling pattern continued to be used by the Contractor and was used for the two Safety 

EdgeSM sections. The Sakai roller operator, however, began to divert back to the initial 

pattern during the compaction operation of the second Safety EdgeSM section. In addition, the 

Sakai roller was removed from the project for mechanical reasons, so the Hypac was the only 

breakdown roller used towards the latter part of paving on the last day of the field study. 

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 gauge readings and the densities of the 

cores suggest that adequate density was obtained for this mixture away from the edge, but the 

density was low near the edge. 

The Safety EdgeSM was rolled inconsistently along the project. The rolling pattern used 

along most of the project, however, was that the first pass of the Sakai breakdown roller was 

along the Safety EdgeSM with the roller extended over the edge of the HMA mat by about 4 

to 6 inches (refer to Figures 18 and 20). As noted above, the Sakai roller operator did divert 

back to initially rolling the mat away from the edge and delayed rolling the edge until the last 

pass in different locations (refer to Figures 18 and 20). For the initial rolling pattern, the edge 

of the mat along the Safety EdgeSM received only one pass of the breakdown roller. The exact 

locations of the different rolling patterns were not identified along the project. 

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

compaction operation. In addition, the Safety EdgeSM did not shove out, or stand up, during 

the compaction operation. Figure 21 shows the surface texture of the finished HMA mat 

along the project. The surface texture and condition was relatively uniform throughout the 

project. 
25

Figure 21. Surface texture of the 9.5 mm HMA overlay after final rolling. 

HMA Mixture Characteristics and the Safety EdgeSM

The HMA mixture design data was obtained from the Mississippi DOT, as well as data 

collected during construction from Falcon Contracting. The HMA mixture design parameters 

are documented in the Field Evaluation Form, which is a separate document to this field 

report. The HMA mixture volumetric properties and gradation are considered reasonable. 

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 temperature of the HMA being delivered to 

the project site was reported to be 295 to 305 °F. Mix temperature and the distance between 

the end of the auger and screed end plate, however, are not believed to be contributing factors 

to the steeper slopes. 

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

end of the Safety EdgeSM device. Figure 22 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. A reason for the steeper slope, however, could be related to the bent shaft of the 

Safety EdgeSM device. 
26

Figure 22. HMA under and behind the screed; the HMA was not being pushed to the end of 

the Safety EdgeSM, which resulted in a steeper slope prior to rolling. 

Note: HMA behind the 

screed. HMA was not being 

pushed to the end of the 

Safety EdgeSM, so the slope 

prior to rolling was steeper 

than 30°. 
27

Figure 23. One of the narrow bridges located on the project (about 22-feet wide). 

Other Observations Related to Site Features 

As reported earlier in the document, two narrow bridges were located within the project 

limits. One of these was located within the non-Safety EdgeSM section (refer to Figure 23). 

The first narrow bridge was located within the non-Safety EdgeSM section. The contractor 

was able to retract the extension on the shoulder side of the paver, so that paving across the 

bridge did not result in any problem. The Safety EdgeSM sections were paved the following 

day and none of the narrow bridges were encountered. 

The contractor voiced a concern about being unable to retract the extension on the shoulder 

side of the paver sufficiently, so that the paver operator would not have to steer the paver 

closer to the centerline and retract the other extension. Steering the paver closer to the 

centerline and retracting the other extension could potentially create a longitudinal joint that 

would be difficult to match and compact (refer to Figure 23). 

The other concern of the contractor was that the smoothness of the mat would decrease in 

those areas, and smoothness was a pay item (refer to Figure 24). The contractor requested 

that the Mississippi DOT permit the Safety EdgeSM device to be removed in those areas. It is 

unknown whether the Mississippi DOT permitted the contractor to remove the Safety EdgeSM

device in those areas. 
28

Figure 24. Longitudinal Profile Testing of Final Surface of Overlay 

Findings and Conclusions 

As previously stated, the objective of this field study was to evaluate the quality of the inplace 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 related to the long term performance of the HMA 

mixture and Safety EdgeSM. 

 The average slope of the Safety EdgeSM was 37°, exceeding the target value of 30°. 

The shaft or screw of the Safety EdgeSM was bent. The bend in the rod or shaft may 

have resulted in a steeper angle because HMA was observed between the screed end 

plate and Safety EdgeSM device. 

 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. 
29

 Breakdown and finish rolling did not steepen the slope of the Safety EdgeSM, even 

when the first pass of the vibratory roller was over the Safety EdgeSM. Based on 

visual observations of the mix behavior under the Sakai roller, the 9.5 mm mixture 

shoved out more at the surface by delaying rolling of the outer 6 to 12 inches of the 

mat, in comparison to rolling the Safety EdgeSM first and extending the roller’s edge 

over the Safety EdgeSM. It is expected, however, that this observation or finding will 

be mixture dependent. The Contractor’s stated opinion was that the revised rolling 

pattern was better than the initial pattern used at the beginning of the project. 

 The contractor did obtain adequate density within the interior of the mat, and adjacent 

to the Safety EdgeSM in some areas. The variability in densities adjacent to the Safety 

EdgeSM is believed to be related to the inconsistency in rolling the Safety EdgeSM, as 

explained in the field report. Although the rolling pattern of the Safety EdgeSM will 

be dependent on the mixture properties, it is recommended that the Safety EdgeSM be 

rolled first and not delayed, as recommended in some of the literature for rolling the 

Safety EdgeSM. It is believed that the air voids adjacent to the Safety EdgeSM would 

have been less than 10 percent if the edge was rolled consistently by overhanging the 

roller over the mat’s edge by 4 to 6 inches. 

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

surface texture was dense. Water beads were observed on the surface after rains that 

occurred during one of the evenings during the paving operation. This observation 

indicates that permeability of the HMA overlay is low. 

 HMA 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 shoulder material windrowed along the roadway from the trenching operation to widen 

the road is planned to be used as the backing material for the Safety EdgeSM. The Safety 

EdgeSM should be inspected after the shoulder material has been placed to the final pavement 

elevation. Monitoring of this site would be beneficial in evaluating the long-term 

performance of the Safety EdgeSM.
A-1

APPENDIX A. DATA TABLES FROM FIELD MEASUREMENTS 

This section of the field report provides a listing of the field measurements recorded during 

the paving operations. 

Table A-1. Safety EdgeSM Slope Measurements; After Final Rolling 

Table A-2. Safety EdgeSM Slope Measurements; Prior to Rolling with Primary Roller 

Width of Taper Thickness Slope

5 430+00 2.00 1.50 36.9

431+00 2.50 1.75 35.0

6 432+00 1.75 1.50 40.6

Driveway 432+50 6.00 3.50 30.3

433+00 3.00 2.00 33.7

434+00 3.50 2.50 35.5

440+00 2.00 1.50 36.9

7 441+00 2.50 2.00 38.7

442+00 1.50 1.25 39.8

8 443+00 3.75 3.00 38.7

444+00 1.75 1.50 40.6

Mean Value 2.75 2.00 36.97

Standard Deviation 1.304 0.716 3.187

Coefficient of Variation 47.4 35.8 8.6

Core/Section ID

Station

Safety Edge

Area #3; Safety Edge Section

Section Identifier

Area #2; Safety Edge Section

Width of Taper Thickness Slope

A 2.50 2.00 38.7

B 2.75 2.25 39.3

C 2.25 2.25 45.0

D 3.50 2.50 35.5

E 2.50 2.25 42.0

Mean Value 2.700 2.250 40.10

Standard Deviation 0.481 0.177 3.584

Coefficient of Variation 17.81 7.86 8.94

Slope measurements taken before rolling the safety edge 

within an independent area to determine the change in 

slope after rolling. No cores were taken in this area.

Section Identifier

Core/Section ID

Station

Safety Edge
A-2

Table A-3. Slope Measurements Along Non-Safety EdgeSM Portion; After Final Rolling 

Table A-4. Nuclear Density Adjustment Ratios; Core Density/Nuclear Density 

Width of Taper Thickness Slope

397+00 2.00 2.50 51.3

1 398+00 2.00 3.50 60.3

399+00 2.00 2.75 54.0

400+00 2.50 3.00 50.2

401+00 3.00 3.50 49.4

402+00 3.00 3.00 45.0

2 403+00 2.00 2.50 51.3

404+00 2.00 3.00 56.3

3 405+00 2.75 2.50 42.3

Long. Crack 406+00 2.00 2.25 48.4

4 407+00 1.50 1.75 49.4

Mean Value 2.25 2.75 50.72

Standard Deviation 0.487 0.524 4.971

Coefficient of Variation 21.7 19.1 9.8

Area #1; Control, Non-Safety Edge Section

Section Identifier

Core/Section ID

Station

Safety 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

A – Adjacent 

to Edge

B – 3 feet 

from Edge

1 Eastbound 398+00 Non-Safety Edge 129.1 137.8 128.8 138.5 1.002 0.995 129.44 139.47

2 Eastbound 403+00 Non-Safety Edge 131.6 139.2 129.8 140.0 1.014 0.994 130.45 140.98

3 Eastbound 405+00 Non-Safety Edge 130.5 138.2 128.2 135.6 1.018 1.019 128.84 136.55

4 Eastbound 407+00 Non-Safety Edge 127.5 135.8 128.7 133.4 0.991 1.018 129.34 134.33

5 Eastbound 430+00 Safety Edge 133.4 140.0 130.9 139.3 1.019 1.005 131.55 140.28

6 Eastbound 432+00 Safety Edge 130.0 135.8 131.4 135.8 0.989 1.000 132.06 136.75

7 Eastbound 441+00 Safety Edge 131.5 140.0 132.3 138.0 0.994 1.014 132.96 138.97

8 Eastbound 443+00 Safety Edge 133.9 136.4 131.8 134.7 1.016 1.013 132.46 135.64

130.94 137.90 130.24 136.91 1.005 1.007 130.89 137.87

2.133 1.760 1.570 2.364 0.0128 0.0101 1.578 2.381

1.63 1.28 1.21 1.73 1.27 1.00 1.21 1.73

Core # Lane Direction Station Type of Section Density of Cores Nuclear Density Values Adjustment Ratio Adjusted Nuclear Values

Area #1; Control Section, NonSafety Edge

Area #2; Safety Edge Section

Area/Location

Mean

Standard Deviation

Coefficient of Variation
A-3

Table A-5. Density Readings Made with a Nuclear Density Gauge (Troxlor Gauge 3440) 

Cores 1-4 Maximum Specific Gravity of Mix: 2.357 Max. Density: 147.08

Cores 5-8 2.355 Max. Density: 146.95

A= 1.005

Maximum Specific Gravity of Mix:

B= 1.007

Adjustment Ratios for Nuclear 

Gauge:

Location/Area

Core Location Lane Direction Station Type of Section Nuclear Densities Adjusted Nuclear Values

HMA 

Thickness, in.

Air Voids, %

Area #2

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

5 Eastbound 430+00 Safety Edge 130.9 139.3 131.55 140.28 1.50 10.48 4.54

Eastbound 431+00 Safety Edge 128.2 135.7 128.84 136.65 1.75 12.32 7.01

6 Eastbound 432+00 Safety Edge 131.4 135.8 132.06 136.75 1.50 10.13 6.94

Driveway Eastbound 432+50 Safety Edge 3.50

Eastbound 433+00 Safety Edge 129.6 137.2 130.25 138.16 2.00 11.37 5.98

Eastbound 434+00 Safety Edge 132.1 136.1 132.76 137.05 2.50 9.66 6.74

Eastbound Safety Edge

Eastbound 440+00 Safety Edge 132.3 136 132.96 136.95 1.50 9.52 6.80

7 Eastbound 441+00 Safety Edge 132.3 138 132.96 138.97 2.00 9.52 5.43

Eastbound 442+00 Safety Edge 129.7 135.8 130.35 136.75 1.25 11.30 6.94

8 Eastbound 443+00 Safety Edge 131.8 134.7 132.46 135.64 3.00 9.86 7.69

Eastbound 444+00 Safety Edge 128.8 134.8 129.44 135.74 1.50 11.91 7.63

Eastbound Safety Edge

Area #3

Average Value 130.71 136.34 131.36 137.29 2.00 10.61 6.57

1.523 1.433 1.531 1.443 0.716 1.042 0.982

Coefficient of Variation 1.17 1.05 1.17 1.05 35.79 9.82 14.95

Standard Deviation

Area #1

Eastbound 397+00 Non-Safety Edge 2.00

1 Eastbound 398+00 Non-Safety Edge 128.8 138.5 129.44 139.47 3.50 11.99 5.17

Eastbound 399+00 Non-Safety Edge 131.3 139.7 131.96 140.68 2.75 10.28 4.35

Eastbound 400+00 Non-Safety Edge 127.7 137.9 128.34 138.87 3.00 12.74 5.59

Eastbound 401+00 Non-Safety Edge 129.0 134.8 129.65 135.74 3.50 11.85 7.71

Eastbound 402+00 Non-Safety Edge 124.8 136.6 125.42 137.56 3.00 14.72 6.48

2 Eastbound 403+00 Non-Safety Edge 129.8 140.0 130.45 140.98 2.50 11.31 4.15

Eastbound 404+00 Non-Safety Edge 128.0 133.8 128.64 134.74 3.00 12.54 8.39

3 Eastbound 405+00 Non-Safety Edge 128.2 135.6 128.84 136.55 2.50 12.40 7.16

Long. Crack Eastbound 406+00 Non-Safety Edge 127.5 135.4 128.14 136.35 2.25 12.88 7.30

4 Eastbound 407+00 Non-Safety Edge 128.7 133.4 129.34 134.33 1.75 12.06 8.67

Eastbound Non-Safety Edge

128.38 136.57 129.02 137.53 2.70 12.28 6.50

1.681 2.362 1.690 2.379 0.568 1.149 1.617

1.73 1.31 1.73 21.01 9.36 24.90

Average Value

Standard Deviation

Coefficient of Variation 1.31
A-4

Photographs of the Cores Recovered from the Project 

This section of the field report provides a photograph of each core set that was recovered for 

laboratory density testing. 

Core 8B

Core 8A

Core 7B

Core 7A

Core 8B

Core 8A

Core 7B

Core 7A
A-5

Core 6B

Core 6A

Core 5B

Core 5A

Core 6B

Core 6A

Core 5B

Core 5A
A-6

Core 4B

Core 4A

Core 3B

Core 3A

Core 4B

Core 4A

Core 3B

Core 3A
A-7

Core 2B

Core 2A

Core 1B

Core 1A

Core 2B

Core 2A

Core 1B

Core 1A