Safety Edge SM

Demonstration Project 

Kearney, Nebraska 

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 along State Route 10 (referred to as 

Pleasanton South) just north of Kearney, Nebraska. These observations and data are to be 

used with similar information from other Safety Edge SM projects to facilitate the 

development of standards and guidance for Safety Edge SM 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 measured during construction on July 

19 and 20, 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 Edge SM device. 
ii

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

3. Title and Subtitle 

Safety EdgeSM Project, Kearney, Nebraska 

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 t o 

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 Edge SM 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 Kearney, Nebraska. The TransTech Shoulder Wedge Maker 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, 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 

27 

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 Safety EdgeSM............................................................................................ 2

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

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

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

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

Slope Measurements ............................................................................................................... 7

Cores ....................................................................................................................................... 9

Nuclear Density Results ........................................................................................................ 10

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

OBSERVATIONS MADE DURING PAVING WITH THE SAFETY EDGESM ........................................ 13

Surface Preparation .............................................................................................................. 13

Placement/Paving Operations .............................................................................................. 13

Compaction Operations ........................................................................................................ 16

HMA Mixture Characteristics and the Safety EdgeSM .......................................................... 26

Other Observations ............................................................................................................... 26

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

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

PHOTOGRAPH OF SELECTED CORES.............................................................................................. 4
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 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. 

Concern was also acknowledged regarding the long term performance of the Safety EdgeSM. 

It was the opinion of some construction personnel that the Safety EdgeSM will “break off” 

during the first year because of local farm traffic. The outside wheel of these farm vehicles is 

located directly over the Safety EdgeSM. The shoulder condition is soft in the spring and 

some of the construction personnel speculate that the heavy duals of the local traffic will 

break the Safety EdgeSM from the mainline pavement. One of these vehicles was observed 

during the last day of the site visit, but a photograph was not taken. 

Slope of the Safety EdgeSM

 The average slope of the Safety EdgeSM was found to be 34°. It was the opinion of 

construction personnel that the slope of the Safety EdgeSM device would need to be 

flattened to about 20 to 25° to meet the 30° desired slope. 

Placement 

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

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. 

 Both contractor and agency personnel voiced a concern that the spring stiffness is too 

high and the travel length too short. In paving across intersections or in areas with higher 

longitudinal profile, the Safety EdgeSM device may raise the screed relative to the profile 

set by the longitudinal ski. 
2

Compaction 

 The HMA density or percent compaction of the non-Safety EdgeSM section was found to 

be the same as for the Safety EdgeSM sections that were compacted using the same rolling 

pattern. 

 The sections for which the rolling pattern was revised to overhang the rollers over the 

edge of the unconfined mat resulted in slightly lower air voids and higher densities as 

compared to the sections where rolling the Safety EdgeSM was delayed and only one pass 

of the vibratory roller was used during breakdown rolling. 

 The air voids of the interior HMA mat had a mean value varying from 6.6 to 8.5 percent 

for the different sections. The air voids determined along the edge of the mat varied 

from 7.8 to 15.9 percent. 

Shoulder Construction 

 A combination of millings, aggregate and soil will be used as shoulder material. 

Placement of the shoulder 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 2.0 inches. The average overlay thickness fo

the Safety EdgeSM sections was found to be 1.5 to 2.1 inches. 

r 

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 10 just north of Kearney, Nebraska, with and without the 

use of the Safety EdgeSM device. The paving contractor for this project was Vontz Paving. 

The Safety EdgeSM device was provided to NDOR by the Federal Highway Administration 

(FHWA), and was added to the project after it was awarded. The contractor, however, did not 

request additional payment related to the Safety EdgeSM (HMA was paid by the ton). The 

Contractor used the TransTech Shoulder Wedge Maker device 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 in Buffalo County, as shown in Figure 1. The project started 

just south of the intersection between Hawk Road and Homestead Road (located one block 

east of SR 10), and ended on the south end of the Pleasanton City Limits. The portion of the 

project for the Safety EdgeSM sections were located south of the intersection with 235th Road, 

while the non-Safety EdgeSM section was located north of 235th Road – all in the northbound 

lane. 

Pavement Structure and Project Conditions 

The project consisted of milling the existing surface to a depth of about 2 inches (basically 

removing the existing wearing surface and some of the underlying layer) and placing a 2 inch 

lift of a 12.5 mm HMA mix over the existing HMA pavement. Figure 2 provides a general 

view of the 2 inch HMA overlay and typical cross section of the pavement. Figure 3 provides 

a general view of the roadway for this project. In preparation for the HMA overlay, the 

following activities and repairs were made. 

 The existing shoulder was graded to remove grass and other debris; no other surface 

preparation along the shoulder was completed. Figures 2 and 4 show the shoulder that 

was graded prior to placement of the HMA overlay and Safety EdgeSM.

 Full depth patches were placed in selected areas of the roadway where the subgrade 

or subsurface layer was found to be soft. Figure 5 shows a full-depth HMA patch that 

was used to repair the roadway prior to overlay placement, and shows depressions 

caused by the paver and belly-dump trucks delivering the 12.5 mm HMA mixture to 

the project site. The full-depth HMA patch was placed across the entire lane width. 

 An emulsion tack coat was placed on the milled surface and patched areas. 
4

Approximate starting 

point of the project. 

Safety EdgeSM portion of the 

project ended at the southern 

part of the Pleasanton city 

limits. N 

1.b. Map of Area Showing Approximate Limits of Project and other Roadways. 

1.a Copy of Plan Sheet Showing Limits of Project Station Numbers. 

Beginning Station: 

413.56.00 

Ending Station: 

941.39.6800 

Figure 1. Location of Site. 
5

Planned 2.0 inch HMA 12.5 mm Overlay 

Existing HMA Pavement; 

Surface Milled about 2.0 

inches Prior to Overlay 

24-Foot Roadway Width 

Full-depth HMA patch placed full lane 

width in localized areas with soft 

pavement layers. 

Confined longitudinal 

construction joint. Both sides of roadway 

were graded to remove 

grass and other debris 

prior to placing the 

HMA overlay & Safety 

EdgeSM. 

Figure 2. 12.5 mm HMA overlay being placed in one direction where the overlay in the 

opposite lane has already been placed. 
6

Figure 3. General overview of project location; 

view is towards the north. 

Figure 4. Graded shoulder ready for placing 

shoulder material. 

Figure 5. Close-up of the full-depth patch area with surface depressions from the belly-dump 

trucks and paver. 
7

The ditches along the edge of the pavement were generally shallow (2 to 5 feet in depth) with 

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

had been graded on each side of the roadway prior to visiting the project. A combination of 

millings, aggregate and soil will be used as shoulder material. The shoulder material was 

scheduled to be graded back to the Safety EdgeSM near the end of this rehabilitation project; 

after overlay placement. 

Field Evaluation 

 Five sections were identified and marked during the paving operation; four Safety EdgeSM

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

sections included within this project. 

1. Area #1: Northbound lane; Safety EdgeSM section located from station 652+20 to 

station 656+20. 

2. Area #2: Northbound lane; Safety EdgeSM section located from station 694+00 to

station 698+00. 

3. Area #3: Northbound lane; Safety EdgeSM section located from station 569+15 to

station 573+15. 

4. Area #4: Northbound lane, Safety EdgeSM section located from station 613+71 to 

station 617+71. 

5. Area #5: Northbound lane, non-Safety EdgeSM section located from station 720+00 to 

station 725+00. 

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

Slope measurements were taken using a 4-foot aluminum straight-edge 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). 

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

cores were obtained at five different locations (4 within the Safety EdgeSM sections and 1 

within the non- Safety EdgeSM section). 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 was not measured along this project because the 2.0 inch 

HMA overlay was considered a temporary repair to this roadway. Agency personnel noted 

that they expect this roadway to need additional strengthening and rehabilitation within 5 

years. 

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

for all four test sections was found to be 34°. Table A-1 in Appendix A contains slope 

measurements recorded at each individual measurement location. Figure 8 includes a 

comparison between the slope of the Safety EdgeSM after final rolling and thickness of the 
8

Safety EdgeSM for the four test sections. As shown, there appears to be no correspondence 

between thickness and the slope of the Safety EdgeSM.

A 

B 

Toe of the slope 

Breakpoint 

Figure 6. Measurement of the Safety EdgeSM slope angle. 

Figure 7. Troxler nuclear density gauge used to measure HMA density. 
9

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

edge of the HMA overlay. 

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

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

established for future performance reviews. Thus, the slope of the Safety EdgeSM was found 

to be slightly steeper than what was planned. 

Cores 

A total of ten 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 adjustment factors for the nuclear density gauge readings taken adjacent to the 

edge and within the center of the mat. Table A-2 in Appendix A includes a summary of the 

bulk specific gravities (saturated surface dry) converted to bulk densities and the adjustment 

factors. Figure 9 shows the location of the cores and nuclear density gauge readings relative 

to the edge of the HMA mat. Figure A-1 in Appendix A shows five of the ten cores 

recovered from the roadway. 

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). As shown, one of the densities of the cores taken along the edge is 

extremely low and considered an outlier. The core densities taken along the pavement’s edge 

are approximately equal for the Safety EdgeSM and non-Safety EdgeSM sections. 
10

Nuclear Density Results 

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

readings were recorded at each station or location; one reading was taken at a point adjacent 

to the Safety EdgeSM and one near the center of the steel drum roller. The nuclear gauge was 

positioned parallel to the pavement edge (refer to Figure 7). The nuclear gauge readings at 

each point are listed in Table A-3 in Appendix A. 

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

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

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 the 

edge). 

Location A; adjacent to 

the edge of the mat where 

nuclear density readings 

were made and a core was 

extracted from the overlay. 

Location B; the 

approximate center of the 

double drum steel wheel 

roller used to compact the 

HMA overlay where 

nuclear readings were 

made and a core was 

extracted from the overlay. 
11

Figure 10. Comparison of core densities adjacent to the edge of pavement and near center of 

the steel drum rollers. 

Nuclear gauge 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 a 

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

determined for the nuclear gauge readings taken at the edge of the HMA mat and near the 

center of the steel drum roller being used to compact the HMA mat. The following lists the 

average adjustment factors determined for this project: 

Location Adjustment Factor 

Near Center of Steel Drum 1.009 

Adjacent to Safety EdgeSM 1.026 

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 

adjustment factors are included in Table A-3 in Appendix A. 

Figure 12 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 12 also 

includes a comparison of the HMA air voids between both of these areas. As expected, the 

air voids are higher adjacent to the Safety EdgeSM in comparison to 3-feeet from the Safety 

EdgeSM. The other observation from this data and comparison is that the densities and air 

voids are similar between the Safety EdgeSM and non-Safety EdgeSM measurements adjacent 

to the edge of the HMA mat. 

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 air voids or densities. 

Outlier 
12

Figure 11. Comparison of the nuclear gauge readings and densities measured from cores.

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.
13

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

Longitudinal Profile Measurements 

As noted above, the longitudinal profile was not measured along this project because the 2.0 

inch HMA overlay was considered a temporary repair to this roadway. Agency personnel 

noted that they expect this roadway to need additional strengthening and rehabilitation within 

5 years. 

Observations Made During Paving with the Safety EdgeSM

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

operations. 

Surface Preparation 

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

HMA overlay. 

1. Full-depth patches were placed in selected areas along the project where the 

subsurface pavement layers and subgrade were weak or soft. Some of the areas after 

patching were considered weaker than desirable (refer to Figure 5). 

2. An emulsion was applied to serve as a tack coat for the HMA overlay. The 

application of the tack coat was uniform and covered the entire surface. 

Placement/Paving Operations 

Figure 14 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 15 shows the TransTech Shoulder Wedge 
14

Maker device attached to the screed. The HMA overlay was placed in windrows using bellydump trucks. The use of windrows and associated paving equipment allowed the paver to 

place the HMA at a constant and uniform rate with few stops of the paver. 

Figure 16 shows the slope and surface texture of the Safety EdgeSM. The contractor 

superintendent/owner recommended that the Safety EdgeSM device be an automated system 

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

Figure 14. Equipment used to place the HMA overlay. 
15

Figure 15. TransTech Shoulder Wedge Maker device attached to the screed. 
16

Figure 16. Typical surface texture and slope of the Safety Edge SM sections. 

Compaction Operations 

Figure 17 shows the two rollers that were used to compact the 12.5 mm HMA mixture. The 

primary or breakdown roller was a Caterpillar double drum vibratory (CB 534D), while the 

finish roller was an Ingersoll-Rand double drum vibratory (DD118 420HFA). The field 

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

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

point on the mat receiving a pass of the roller). In summary, each roller had 5 passes with 2 

coverages, except for the area adjacent to (within 6 inches) and along the Safety Edge SM, 

which only received one pass of the breakdown roller. 

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. 
17

Figure 17. Rollers used for compacting the 12.5 mm HMA overlay mixture.

Caterpillar double 

drum vibratory steel 

wheel roller used in 

breakdown or 

primary position for 

compacting the 

HMA overlay. 

Ingersoll-Rand double 

drum vibratory steel 

wheel roller used in 

the vibratory and 

static mode that was 

used in the finish 

position for 

compacting the HMA 

overlay. 

Project personnel indicated that during the first day of paving significant effort was expended 

to assess various rolling patterns. It was clear that NDOR and contractor project personnel 

considered this as a demonstration type project and worked cooperatively to assess ho w best 

to construct the Safety EdgeSM. The goal of the rolling pattern assessment was to obtain as 

close to a 30 degree Safety EdgeSM slope after compaction was completed. 

The first rolling pattern used was the standard rolling pattern the contractor uses for this 

HMA mix under similar conditions. The first pass of the breakdown roller had the roller’s 

edge extended over the Safety EdgeSM by about 6 inches. This resulted in the Safety Edge SM

slope being pushed close to vertical. This did not accomplish the goal of maintaining a 30 

degree slope, so several different rolling patterns were attempted at the beginning of the 

project (i.e., changes in location of first pass of roller, waiting some time before rolling 

commenced near Safety EdgeSM, etc.). NDOR and contractor personnel agreed on the rolling 

pattern to use for production that balanced obtaining a reasonable Safety Edge SM slope with 
18

adequate HMA production. Figure 18 shows the variation in the location of the roller’s edge 

along the Safety EdgeSM. 

Figure 18. Initial rolling pattern; edge of the breakdown roller varied along the Safety 

EdgeSM, prior to finish rolling. 

Initial rolling pattern; rolling the 

Safety EdgeSM was delayed, and the 

location of the steel wheel roller 

varied along the edge from 

successive passes. 

Initial rolling pattern; rolling the 

Safety EdgeSM was delayed, and the 

location of the steel wheel roller 

varied along the edge from 

successive passes. 

The contractor was asked to revise the initial rolling pattern for a couple of the test sections. 

Two of the five sections, were rolled differently than the majority of the project to determine 

if different rolling patterns had an impact on the density of the unconfined edge (Safety 

EdgeSM and non-Safety EdgeSM sections). The following summarizes the two rolling patterns 

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

Initial Rolling Pattern ─ This pattern was used along most of the project, and for test 

sections 2, 3 and 4 (refer to Table A-1 in Appendix A.). 

 Caterpillar Breakdown Roller: The following describes the pattern used by the 

breakdown roller for rolling the mat in locations with a confined longitudinal 
19

centerline joint. The rolling pattern for an unconfined centerline joint is described in a 

latter part of this section. 

o First pass was along the longitudinal centerline joint in the static position 

along the cold side of the joint (refer to Figure 19.a; cold-side-pinch). 

o Second pass was along the longitudinal centerline joint but on the hot side of 

the joint in the vibratory mode (low frequency, low amplitude [refer to Figure 

19.b]). 

Third pass was near the center of the mat but about 6 to 12 inches from the 

Safety EdgeSM; also in the vibratory mode (refer to Figure 20). 

o

o Fourth pass was over the same location as for the third pass but in the reverse 

direction and in vibratory mode. 

o Fifth pass of the roller was delayed for a short time period and along the 

Safety EdgeSM (edge of drum varied from near the edge to about 6 inches 

from the Safety EdgeSM, refer to Figure 18) in the vibratory mode. 

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

vibratory mode. In some areas, the roller’s edge was located slightly away 

from the Safety EdgeSM. 

o Seventh pass; same location as for the second pass, but in the reverse direction 

in vibratory mode. 

It was observed that only five passes of the breakdown roller was applied in a few areas of 

the roadway where the adjacent lane had not already been paved. In summary, Passes #6 and 

#7 were not used or omitted from the rolling pattern of the breakdown roller. 

The pattern used to compact areas with an unconfined centerline construction joint required 

fewer passes. For the first pass the roller’s edge was located about 6 inches from the 

centerline joint or unconfined edge; for the second pass the roller’s edge was extended over 

the unconfined edge by about 2 to 4 inches; for the third pass the roller’s edge was located 

about 6 to 12 inches from the Safety EdgeSM; the fourth pass was the same as for the third 

pass; and the fifth pass was delayed and located along or slightly over the Safety EdgeSM. 

The delay in rolling the Safety EdgeSM caused the roller operator to increase the speed of the 

breakdown roller to keep up with the paver. The increase in speed resulted in chatter in 

localized areas of the mat surface (roller being operated too fast for the frequency selected). 

The other important point is that the outer edge of the mat (6 to 12 inches from the Safety 

EdgeSM) only received one pass of the breakdown roller in some areas prior to the first pass 

of the Ingersoll-Rand roller (refer to Figure 21). 

 Ingersoll-Rand Finish Roller: The first pass of the finish roller was delayed up to 

about 2 hours after paving to retain the angle of the Safety EdgeSM.

o First pass of the roller (refer to Figure 21) was along and over the Safety 

EdgeSM (the edge of the roller was about 4 to 6 inches over the Safety EdgeSM) 

in the vibratory mode (high frequency, low amplitude). 

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

in vibratory mode. 
20

o Third pass was about 6 inches from the centerline longitudinal joint in the 

vibratory mode. 

o Fourth pass was over the centerline longitudinal joint in vibratory mode. 

o Fifth pass was along the center of the lane in the static mode. 

The finish roller appeared to remove most of the chatter caused by the breakdown roller. The 

finish roller did not eliminate the longitudinal roller mark left by delaying the breakdown 

roller along the outside edge of the mat (refer to Figure 22). It is expected that this mark will 

eventually result in a longitudinal crack along the edge of the mat. 

(a) First pass of 

Caterpillar 

breakdown roller in 

static mode along 

the cold-side of the 

longitudinal joint. 

(b) Second pass of 

Caterpillar 

breakdown roller in 

vibratory mode 

along the hot-side of 

the longitudinal 

.joint.
21

Figure 19. Initial rolling pattern; cold-side-pinch was used to compact the confined 

longitudinal construction joint. 
22

Pass #3 of Caterpillar roller is 6 to 12 inches from the edge of the mat. 

Figure 20. Rolling the unconfined edge with the vibratory steel wheel roller. 

Note the location of the 

roller’s edge for the third 

pass. This may result in a 

longitudinal crack with time 

where the passes were along 

the same line and the rolling 

of the edge is delayed. 
23

Figure 21. First pass of the Ingersoll-Rand finish roller along the Safety EdgeSM.

Figure 22. Longitudinal mark left by delaying the breakdown rolling of the Safety EdgeSM; 

image taken after finish rolling. 
24

Revised Rolling Pattern ─ At the request of the field evaluation team, this pattern was used 

for a couple of the test sections; one of the Safety EdgeSM sections (test section 1, refer to 

Table 1) and the non-Safety EdgeSM section (test section 5, which was the non-Safety EdgeSM

section). 

 Caterpillar Breakdown Roller: The only difference between the initial rolling pattern 

used along most of the project was that the first two passes of the breakdown roller 

were in the vibratory mode with the edge of the roller extended over the Safety 

EdgeSM by about 4 to 6 inches. 

o First pass of roller was along the Safety EdgeSM in the vibratory mode with 

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

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

and in vibratory mode. 

o Third pass was along the longitudinal centerline joint with the roller’s edge 

extended over the joint by 4 to 6 inches and in vibratory mode. 

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

and in vibratory mode. 

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

 Ingersoll-Rand Finish Roller: The revised rolling pattern was the same as used for 

the initial rolling pattern; no change in rolling pattern was made to the finish roller. 

Figure 23 shows a comparison of the adjusted nuclear density gauge readings and air voids 

adjacent to the Safety EdgeSM in comparison to the center of the breakdown roller (3-feet 

from the edge) for the two rolling patterns. The air voids adjacent to the edge were dependent 

on the rolling pattern used to compact the HMA unconfined edge. The following summarizes 

the average air voids and slopes of the Safety EdgeSM for the two rolling patterns in 

comparison to the initial or standard pattern that was being used by the contractor. 

Rolling Pattern 

Average Slope of 

Safety EdgeSM

Air Voids 

Adjacent to Edge 

Delay Rolling the Safety EdgeSM Pattern 34 12.3 

No Delay in Rolling the Safety EdgeSM Pattern 34 10.4 

As tabulated above and shown in Figure 23, rolling the Safety EdgeSM first without delay 

and extending the edge of the breakdown roller over the Safety EdgeSM by 4 to 6 inches 

resulted in lower air voids and higher densities without significantly steepening the average 

slope of the Safety EdgeSM, as compared to delaying rolling of the Safety EdgeSM. 

No shoving or tearing of the mixture was observed during the compaction operation. In 

addition, the Safety EdgeSM did not shove out, or “stand up”, during the compaction 

operation. Figure 24 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 23. Comparison of volumetric properties between the areas adjacent to the edge and 

center of the steel drum roller for the two different rolling patterns. 

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. 
26

Figure 24. Surface texture of the 12.5 mm HMA overlay after final rolling. 

HMA Mixture Characteristics and the Safety EdgeSM

The HMA mixture design data was obtained from the Nebraska Department of Roads. 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. 

Figure 14 showed the HMA behind the screed and the Safety EdgeSM slope prior to rolling. 

The slope of the Safety EdgeSM prior to rolling was equal to or slightly steeper than the 

planned 30°. The distance between the end of the auger and screed end plate was about 18 

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

the HMA being delivered to the project site was reported to be 310 to 318 °F. Mix 

temperature and the distance between the end of the auger and screed end plate are not 

believed to be contributing factors to the steeper slopes. 

Other Observations 

The following lists some of the observations and comments made by construction personnel. 

 Density along the edge of the HMA mat is a concern. 

 It was also the opinion of construction personnel that the Safety EdgeSM will “breakaway” from the HMA mainline pavement in a short period of time, because of local 

farm traffic where the outer tire is located along the edge of the pavement. NDOR 

personnel indicated that as part of their future Safety EdgeSM efforts, they were 

planning to investigate adding some structural material beneath the Safety EdgeSM to 

alleviate agricultural/heavy vehicle damage. 
27

 The contractor had manufactured a separate Safety EdgeSM device that was used on a 

portion of the project, but not included in any of the test sections established for this 

demonstration project. The contractor’s special device had a longer travel length and 

a weaker spring stiffness. The contractor’s opinion was that the travel length of the 

TransTech device was too short and the spring was too stiff. Project personnel noted 

that the stiff spring and short travel length could cause the screed to rise when paving 

across intersections or when paving over hard surfaces with higher elevations. 

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 related to the long term performance of the HMA

mixture and Safety EdgeSM.

 The average slope of the Safety EdgeSM was 34°, slightly exceeding the target value 

of 30°. Project personnel indicated that the slope of the Safety EdgeSM device may 

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

NDOR personnel indicated that as part of their future Safety EdgeSM efforts, they 

were planning to use Safety EdgeSM equipment with a 20 ̊ slope and more compactive

effort that would allow them to get the rollers on the mat sooner and result in higher 

density and a finished slope closer to 30 ̊.

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

when the first pass of the Caterpillar vibratory roller was over the Safety EdgeSM

along test section 1. Based on visual observations, the mixture did not shove out 

more or less than when the edge of the roller was extended over the Safety EdgeSM

without any delay in rolling the Safety EdgeSM. Project personnel did report that the 

slope did steepen using their standard rolling pattern during the first day of paving. It 

is expected that this observation or finding will be mixture dependent. 

 The contractor did revise the rolling pattern for a short segment to eliminate any delay 

in rolling the Safety EdgeSM and extending the edge of the roller over the Safety 

EdgeSM by 4 to 6 inches (test section 1). The revised rolling pattern increased the 

density of the HMA adjacent to the edge without significantly increasing the slope of 

the Safety EdgeSM. The density of the HMA mat along the Safety EdgeSM is lower 

and the air voids higher in the areas where the Safety EdgeSM was rolled last and only 

received one pass of the Caterpillar steel wheel roller. High air voids have a 

detrimental effect on performance of the mixture. 
28

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

to the Safety EdgeSM in areas with the revised rolling pattern. It is recognized that the 

rolling pattern of the Safety EdgeSM will be dependent on the mixture properties. It is 

expected that as Safety EdgeSM equipment and procedures are enhanced, an 

improvement in efficiently obtaining density will occur. 

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

similar to the areas without the Safety EdgeSM when similar rolling patterns were used 

to compact or roll an unconfined edge. 

 The 12.5 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 just prior to the demonstration project. 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 pavement should be inspected after the final shoulders have been constructed. The 

onsite windrowed material that is a combination of millings, aggregate and soil are planned 

to be used as the unpaved shoulder. Care should be taken to observe the shoulder 

construction and ensure that meets proper relative elevation to the HMA mat. Long term 

monitoring should be conducted of the Safety EdgeSM to assess heavy vehicle impacts on the 

wedge and monitoring to observe how well the coarse-grained shoulder remains in place and 

any deformation or erosion in the shoulder material. 
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 after final rolling. 

Core/Section ID

Station

Safety Edge

Area #2, Northbound Lane

Section Identifier

Area #1,Northbound Lane

Width of Taper Thickness Slope

652+20 3.5 2.125 31.3

652+70 3.25 2.125 33.2

653+20 3.5 2.125 31.3

653+70 3.125 2.25 35.8

C 3-1 654+20 3.25 2.125 33.2

654+70 3.25 2.125 33.2

655+20 3.25 2.375 36.2

655+70 3 1.875 32

656+20 3.75 2.125 29.5

Mean Value 3.32 2.14 32.86

Standard Deviation 0.226 0.132 2.152

Coefficient of Variation 6.82 6.16 6.55

694+00 3.125 2 32.6

694+50 1.625 1.125 34.7

695+00 2.375 1.5 32.3

695+50 2.5 1.75 35

TS-3 696+00 2.5 1.625 33

696+50 2.375 1.625 34.4

697+00 2.5 2 38.7

697+50 2.375 1.75 36.4

698+00 2.625 1.625 31.8

Mean Value 2.444 1.667 34.322

Standard Deviation 0.386 0.265 2.215

Coefficient of Variation 15.8 15.9 6.5

Width of Taper Thickness Slope

569+15 2.5 1.5 31

569+65 0.75 0.75 45

570+15 2.25 1.5 33.7

570+65 2.625 1.75 33.7

C 2-4 571+15 2.125 1.625 37.4

571+65 2 1.25 32

572+15 2 1.375 34.5

572+65 2.75 1.875 34.3

573+15 2.5 1.75 35

Mean Value 2.17 1.49 35.18

Standard Deviation 0.596 0.339 4.102

Coefficient of Variation 27.52 22.82 11.66

613+71 3.375 2 30.7

614+21 3.25 2 31.6

614+71 2.875 2 34.8

615+21 3.5 2.625 36.9

C 2-5 615+71 3.5 2 29.7

616+21 2.375 1.75 36.4

616+71 3 1.875 32

617+21 2.75 1.625 30.6

617+71 2.875 1.625 29.5

Mean Value 3.056 1.944 32.47

Standard Deviation 0.381 0.300 2.842

Coefficient of Variation 12.5 15.5 8.8

Section Identifier

Core/Section ID

Station

Safety Edge

Area #3, Northbound Lane

Area #4, Northbound Lane
A-2

Table A-2. Nuclear density adjustment factors; core density/nuclear density. 

Table A-3. Density readings made with a nuclear density gauge (Troxlor gauge 3440). 

Average

Standard Deviation

Coefficient of Variation

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

A – Adjacent to

Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

A – Adjacent 

to Edge

B – 3 feet 

from Edge

C 3-1 Northbound 654+20 Safety Edge 133.05 141.95 131.60 140.80 1.011 1.008 135.02 142.07

C 2-4 Northbound 571+15 Safety Edge 133.40 140.89 131.60 140.00 1.014 1.006 135.02 141.26

C 2-5 Northbound 615+71 Safety Edge 129.81 140.63 128.00 138.50 1.014 1.015 131.33 139.75

C 3-2 Northbound 722+46 Non-Safety Edge 136.08 139.14 127.9 136.4 1.064 1.020 131.23 137.63

TS-3 Northbound 696+00 Safety Edge 118.35 139.68 130.40 140.60 0.908 0.993 133.79 141.87

133.085 140.458 129.900 139.260 1.026 1.009 133.277 140.513

1.979 1.094 1.847 1.835 0.002 0.010 2.133 1.852

1.49 0.78 1.42 1.32 0.16 1.01 1.60 1.32

NOTE: The density measured on the core TS-3 adjacent to the edge is believed to be in error (the highlighted cells).

The highlighted values noted above was excluded from determining the average adjustment ratio and other statistical values.

2.423 151.2

A= 1.026

B= 1.009

Maximum Specific Gravity of Mix: Max. Density:

Adjustment Ratios for Nuclear 

Gauge:

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

Northbound 652+20 Safety Edge 133.2 141 136.6632 142.269 2.125 9.72 6.02

Northbound 652+70 Safety Edge 2.125

Northbound 653+20 Safety Edge 133.6 141 137.0736 142.269 2.125 9.45 6.02

Northbound 653+70 Safety Edge 2.25

C 3-1 Northbound 654+20 Safety Edge 131.6 140.8 135.0216 142.0672 2.125 10.81 6.15

Northbound 654+70 Safety Edge 2.125

Northbound 655+20 Safety Edge 131.1 137.4 134.5086 138.6366 2.375 11.15 8.42

Northbound 655+70 Safety Edge 1.875

Northbound 656+20 Safety Edge 132.5 139.9 135.945 141.1591 2.125 10.20 6.75

1.051 1.534 1.079 1.547 0.132 0.712 1.022

Lane Direction Adjusted Nuclear Values Air Voids, %

HMA 

Location/Area Thickness, in.

Standard Deviation

Average Value 132.40 140.02 135.84 141.28 2.139 10.26 6.67

Station Type of Section Nuclear Densities

Coefficient of Variation 0.79 1.10 0.79 1.10 6.16 6.94 15.32

Core 

Location

Area #1, Northbound Lane

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

Northbound 694+00 Safety Edge 129.4 138.4 132.76 139.65 2 12.30 7.75

Northbound 694+50 Safety Edge 1.125

Northbound 695+00 Safety Edge 127.1 138.3 130.40 139.54 1.5 13.86 7.82

Northbound 695+50 Safety Edge 1.75

TS-3 Northbound 696+00 Safety Edge 130.4 140.6 133.79 141.87 1.625 11.62 6.29

Northbound 696+50 Safety Edge 1.625

Northbound 697+00 Safety Edge 130.4 139.2 133.79 140.45 2 11.62 7.22

Northbound 697+50 Safety Edge 1.75

Northbound 698+00 Safety Edge 133.2 139.6 136.66 140.86 1.625 9.72 6.95

130.10 139.22 133.48 140.47 1.67 11.82 7.21

2.195 0.944 2.253 0.953 0.265 1.488 0.630

1.69 0.68 1.69 0.68 15.91 12.59 8.74

Average Value

Standard Deviation

Adjusted Nuclear Values

Coefficient of Variation

Nuclear Densities

Location/Area

Core 

Location

Lane Direction Station Type of Section

HMA 

Thickness, in.

Air Voids, %

Area #2, Northbound Lane
A-3

Table A-3. Continued. 

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

Northbound 569+15 Safety Edge 124.5 140.9 127.74 142.17 1.5 15.52 6.02

Northbound 569+65 Safety Edge 0.75

Northbound 570+15 Safety Edge 127.1 137.7 130.40 138.94 1.5 13.75 8.16

Northbound 570+65 Safety Edge 1.75

C 2-4 Northbound 571+15 Safety Edge 131.6 140 135.02 141.26 1.625 10.70 6.62

Northbound 571+65 Safety Edge 1.25

Northbound 572+15 Safety Edge 137.3 137.4 140.87 138.64 1.375 6.83 8.36

Northbound 572+65 Safety Edge 1.875

Northbound 573+15 Safety Edge 128.3 140.1 131.64 141.36 1.75 12.94 6.56

129.76 139.22 133.13 140.47 1.49 11.95 7.14

4.927 1.567 5.055 1.582 0.339 3.344 1.045

3.80 1.13 3.80 1.13 22.82 27.98 14.63

HMA 

Thickness, in.

Air Voids, %

Average Value

Location/Area

Core 

Location

Lane Direction Station Type of Section Nuclear Densities

Standard Deviation

Coefficient of Variation

Adjusted Nuclear Values

Area #3, Northbound Lane

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

Northbound 613+71 Safety Edge 128.9 136.6 132.25 137.83 2 12.53 8.84

Northbound 614+21 Safety Edge 2

Northbound 614+71 Safety Edge 130 138.1 133.38 139.34 2 11.79 7.84

Northbound 615+21 Safety Edge 2.625

C 2-5 Northbound 615+71 Safety Edge 128 138.5 131.33 139.75 2 13.14 7.58

Northbound 616+21 Safety Edge 1.75

Northbound 616+71 Safety Edge 124 137.8 127.22 139.04 1.875 15.86 8.04

Northbound 617+21 Safety Edge 1.625

Northbound 617+71 Safety Edge 129.8 137.5 133.17 138.74 1.625 11.92 8.24

128.14 137.70 131.47 138.94 1.94 13.05 8.11

2.447 0.718 2.511 0.724 0.300 1.660 0.479

1.91 0.52 1.91 0.52 15.45 12.73 5.91

Nuclear Densities Adjusted Nuclear Values

HMA 

Thickness, in.

Air Voids, %

Average Value

Standard Deviation

Lane Direction Station

Coefficient of Variation

Area #4, Northbound Lane

Location/Area

Core 

Location

Type of Section

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

Northbound 720+46 Non-Safety Edge 135.4 137.4 138.92 138.64 8.23 8.42

Northbound 721+46 Non-Safety Edge 133.4 138.8 136.87 140.05 9.59 7.49

C 3-2 Northbound 722+46 Non-Safety Edge 127.9 136.4 131.23 137.63 13.31 9.08

Northbound 722+46 Non-Safety Edge

Northbound 723+46 Non-Safety Edge 127.2 142.6 130.51 143.88 13.79 4.95

Northbound 724+46 Non-Safety Edge 136.1 131.4 139.64 132.58 7.76 12.42

132.00 137.32 135.43 138.56 #DIV/0! 10.54 8.47

4.189 4.061 4.298 4.098 #DIV/0! 2.839 2.707

3.17 2.96 3.17 2.96 #DIV/0! 26.95 31.95

Nuclear Densities Adjusted Nuclear Values

HMA 

Thickness, in.

Air Voids, %

Location/Area

Core 

Location

Lane Direction Station Type of Section

Average Value

Standard Deviation

Coefficient of Variation

Area #5, Northbound Lane
A-4

Photograph of Selected Cores 

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

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

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

Some of the cores did exhibit much larger aggregate than included in the test results for 

mixture design, quality control and other tests, as shown in the picture for two of the five 

cores. Larger aggregate would tend to steepen the slope of the Safety EdgeSM, because those 

larger aggregate would prevent the finer aggregate particles being nearer the bottom of the 

slope. Based on visual observations of the Safety EdgeSM, this is not believed to be the case, 

with the possible exception in a few localized areas. 

Figure A-1. Cores recovered for laboratory density testing.