Project Title:
AIRFIELD MARKING DURABILITY STUDY
Date:
12 March 2014
Organization:
Potters Industries, Inc.
Project Location:
Malvern, PA
_________________________________________
Sightline, LC
Airport Marking Consultants
15483 Enterprise Way
Culpeper, VA 22701
540-825-9660
540-825-9088 (FAX)
DONNA J. SPEIDEL – 540-226-2656 (CELL)
[email protected]
MICHAEL W. SPEIDEL – 540-272-3583 (CELL)
[email protected]
http://www.sightline.us/
EXECUTIVE SUMMARY
Pavement markings on airfields provide guidance to pilots and others operating on airfield
surfaces. Airfield pavement markings are enhanced when installed with glass beads embedded
in the coating. When properly applied according to the Airfield Marking Handbook1, the use of
glass beads provides greater conspicuity through reflectivity. Airfield marking reflectivity
increases pilot preview time and distance recognition at night and low light conditions, which
improves user situational awareness and safety.
Low-index glass beads, Federal Specification TT-B-1325D Type I, are less expensive than highindex glass beads, TT-B-1325D, Type III. Despite the higher initial cost, Type III beads have
superior retro-reflectivity performance and a longer life cycle.
Sightline performed the study documented in this report to determine if the use of high-index
Type III glass beads would result in airfield markings that (1) remained effective longer, (2)
reduced the frequency of maintenance, and (3) reduced the cost of marking maintenance.
Based on reflectivity data recorded at 13 airports across the United States, including military
and commercial, Type III glass beads provide higher levels of retro-reflectivity initially and over
time, resulting in lower maintenance costs.
1
Airfield Marking Handbook, Innovative Pavement Research Pavement Foundation for the Federal Aviation
Administration, published September 2008.
2
1.1 Introduction
Pavement markings provide guidance to pilots and others operating on airfield surfaces. The
markings must be clearly visible during both daylight and darkness, “ensuring that each
[marking] provides an accurate reference to the user.”2
Paint markings deteriorate gradually in terms of and markings are maintained with regular
frequency; often annually. When markings are properly installed using best practices, the
frequency of maintenance can be decreased because the markings remain effective (visible)
longer. Best practices include the use of high-quality materials suitable for the airport’s
environment resulting in effective markings that last multiple years.
The type of glass bead applied has a
significant role in how long the
markings can remain effective during
darkness. There are two families of
glass beads approved for use on
airfields, commonly classified as
“low index” and “high index”. High
index glass beads (e.g. FAA TT-B1952D, Type III) reflect more light
back to its source than low index
glass beads (e.g. FAA TT-B-1952D,
Types I and IV). Type III glass beads
not only last longer, but have higher
retro-reflectivity, are brighter in
appearance, and provide greater
distance recognition, contributing to
higher user situational awareness,
visible in Figure 1.
Figure 1 – Type III beads on arrow heads measured
1100 mcd/m2/lx, Type I on arrow stems measured
350 mcd/m2/lx..
Markings are maintained or repainted when they no longer can be seen clearly. The brightness
of pavement markings is measured in millicandelas per square meter per lx (mcd/m2/lx).
Department of Defense (DoD) specifications require newly installed white markings to have a
minimum reflective level of 200 mcd/m2/lx and 175 mcd/m2/lx for yellow markings.3 By
comparison, a white marking without any glass beads measures 50 mcd/m2/lx.4 A study
conducted by the Federal Aviation Administration’s Technical Center at Atlantic City concluded
that a retro-reflectivity value of 100 mcd/m2/lx for white markings and 70 mcd/m2/lx for
2
Part 139 of the Code of Federal Regulations (CFR) 49, Subsection 311(d)
Unified Guide Specification 32 17 23.00, Section 3.2.2.1. – Reflective Markings, p. 19, April 2006.
4
DOT/FAA/AR-TN02/128 – Paint and Bead Durability Study, Holly Cyrus, May 2003
3
3
yellow markings was the lowest acceptable level of reflectivity.5 Markings below that level are
ineffective and require maintenance.
Studies conducted by the Transportation Research Board and other agencies have concluded
that “minimum retro-reflectivity values are speed dependent. Preview distance is important,
especially at higher speeds [that occur during landings and take-offs of aircraft]. When drivers
[or pilots] are provided with higher reflectivity values, longer preview distances are achieved,
which is desirable from an information acquisition, information processing, and safety point of
view.”6
Several studies conducted over the last decade conclude “Type III beads are brighter and more
visible than Type I at installation.” Those studies also indicated that “the Type III markings
remain brighter longer,”7 and consequently require less maintenance relative to maintaining
retro-reflectivity.
1.2 Objective
Following were the main objectives were of the study:
1. Collect retro-reflectivity readings with LTL-X Retrometer using American Standard Test
Method (ASTM) E1710.
2. Evaluate markings from commercial and military airfields that were at least two years
old.
3. Compare retro-reflectivity measurements of different types of glass beads relative to
the age of both white and yellow markings.
The research team had difficulty finding airport markings with Type I beads that were more
than two or three years old. Two airports that used Type III beads had markings that were over
seven years old.
5
DOT/FAA/AR-TN03/22 – Development of Methods for Determining Airport Pavement Marking Effectiveness,
.Holly Cyrus, March 2003
6
Transportation Research Board, NCHRP Synthesis 306, Long-Term Pavement Marking Practices, 2002, Project 205. Chapter 3, Driver Needs, Retroreflectivity Requirements and Information Through Word and Symbol Markings,
page 14, James Migletz and Jerry Graham, consultants.
7
DOT/FAA/AR-TN05/43- Adsil Glass Coating Study, NAS Jacksonville, FL, Holly Cyrus, August 2004;
DOT/FAA/AR-TN02/128 – Paint and Bead Durability Study, Holly Cyrus, May 2003;
U.S. Army Corps of Engineers, Engineer Research and Development Center, “A Comparative Field Study of
Permastripe™ Polymer Concrete and Waterborne Airfield Markings”, 2007.
4
1.3 Evaluation
Airports were identified where markings
(using either Type I or Type III glass
beads) were applied and/or maintained
one or more years prior.
Once identified, technicians traveled to
each airport to gather retro-reflectivity
readings.
Airports were selected in
different geographic and environmental
regions within the continental United
States so that all weather conditions,
including snowplow activity, would be
represented.
The markings at airports that used Type I
glass beads averaged two years of life for
the markings; markings at airport that
used Type III glass beads averaged four
years life. Figure 2 is a compilation of the
data collected from thirteen airports
throughout the United States.
Retro
351
255
775
664
697
457
749
592
168
219
87
136
402
488
577
371
323
468
269
306
Overall Averages [Type/Color/Age]
Type
Color
Age
Samples
Type I
White
1 year
9
Type I
White
2 years
8
Type III
White
1 year
6
Type III
White
2 years
6
Type III
White
3 years
9
Type III
White
4 years
10
Type III
White
6 years
4
Type III
White
7 years
5
Type I
Yellow
1 year
7
Type I
Yellow
2 years
10
Type I
Yellow
3 years
1
Type I
Yellow
5 years
2
Type III
Yellow
1 year
1
Type III
Yellow
2 years
6
Type III
Yellow
3 years
1
Type III
Yellow
4 years
4
Type III
Yellow
5 years
1
Type III
Yellow
6 years
3
Type III
Yellow
7 years
2
Type III
Yellow
8 years
2
The data demonstrates that retroreflectivity measurements of white and Figure 2. Average Retro-reflective value of aging
yellow markings applied with Type III markings applied with Type I v. Type III glass
beads achieve higher readings initially beads on white and yellow paint.
and over multiple years. The data also
shows markings applied with Type III have a longer effective life cycle.
1.4 Other Research Data
Historical research involving the collection of airfield marking retro-reflectivity data supports
the results of this study. The study referenced in Figure 3 compared a polymer concrete
marking material (Permastripe™) to waterborne paint; and both Type I and Type III glass beads
were used.8
8
U.S. Army Corps of Engineers, Engineer Research and Development Center, “A Comparative Field Study of
Permastripe™ Polymer Concrete and Waterborne Airfield Markings”, 2007.
5
Figure 3 – Comparative retro-reflectivity levels on white and yellow paint that
demonstrates the relative brightness of Type III glass beads compared to Type I glass
beads over 1.8 years. The Permastripe™ material being tested in the study did not
retain glass beads well.
Another study concluded that the “Type III (1.9 IOR) Airport bead had the highest retroreflectivity initially and over time.”9
1.5 Cost Comparison
To illustrate the cost benefit of Type III beads, one of the subject airports, NAS Fort Worth, was
selected for a cost comparison. Two estimates were computed theoretically to hire a
contractor to repaint the airfield markings, first using Type I beads, and second using Type III
beads. As seen in Figure 4, the estimate for Type I beads was $272,832; and in Figure 5, the
estimate for Type III beads was $335,885.
9
DOT/FAA/AR-TN02/128 – Paint and Bead Durability Study, Holly Cyrus, May 2003, page 20.
6
Esti mate - Type I beads
Total Quantities
433,654
Average Production
14455
Projected Work Days
30
Travel Days
2
Total Days
32
Item
Labor
52,662
Equipment
11,200
Fuel
Bond
8,185
54,736
7,200
Cos t
Travel
18,000
Profit
34,848
Material
86,001
Tot Job
272,832
Unit
Quantity
White Paint
SF
177,218
0.50
88,609
Yel low Paint
SF
152,850
0.90
137,565
Black Paint
SF
94,929
0.30
28,479
Hold Bars
SF
8,657
2.10
18,180
237,984
Unit Pri ce Extension
272,832
Figure 4 – Estimate to repaint the markings at NAS Fort Worth using
low index (Type I) glass beads.
Esti mate - TT-B-1325D, Type III Gl as s Beads
Total Quantities
433,654
Average Production
14455
Projected Work Days
30
Travel Days
2
Total Days
32
Item
Labor
52,662
Equipment
11,200
Fuel
Travel
Material
Bond
10,077
68,042
7,200
Cos t
18,000
Profit
40,048
Tot Job
335,885
128,656
Unit
Quantity
White Paint
SF
177,218
0.75
132,914
Yel low Paint
SF
152,850
1.00
152,850
Black Paint
SF
94,929
0.30
28,479
Hold Bars
SF
8,657
2.50
21,643
295,837
Unit Pri ce Extension
335,885
Figure 5 – Estimate to repaint the markings at NAS Fort Worth using
high index (Type III) glass beads.
The graph seen in Figure 6 illustrates the relative cost of Type I beads applied at NAS Fort Worth
over an eight-year period versus the cost of Type III beads applied over the same time line. At
approximately 1-1/4 years, the cost of each type is even, and Type III glass beads are more cost
effective thereafter with a higher return on investment.
7
Figure 6 – Cost comparison of Type I and Type III glass beads over eight years.
Besides the cost effectiveness of fewer airfield painting cycles, lowering the number of paint
layers applied diminishes the likelihood markings can become foreign object debris (FOD)
(Figure 7), and reduces paint removal costs over time. After five marking cycles or an
accumulation of 40 mils of paint, the markings may need to be removed.10
Figure 7 – Each maintenance cycle results in another layer of paint and glass beads. Paint
build up has been related to foreign object debris (FOD).
10
UFGS 32 17 23.00, Part 3, Section 3.1 – Surface Preparation:
“Existing marking paints with paint build-up greater than 1 mm 40 mils shall be completely removed in accordance
with Section 32 01 11.51, unless crack free and determined sound. When tested for adhesion (ASTM D4541), a
sound marking paint must exhibit greater than 0.97 MPa 140 psi adhesion and/or produce 100 percent cohesive
failures within the pavement.”
8
1.6 Conclusions
Type III glass beads are brighter initially and over time when applied well.
The additional cost of Type III glass beads can be justified by the longer, sustained performance
versus Type I glass beads. Over time the cost of using Type I glass beads exceeds that of Type III
due to the greater frequency of painting required to maintain visibility. Further, when markings
are maintained less frequently, as with Type III beads, layers of paint build up are minimized,
reducing the chance for FOD and delaying the need for paint removal.
Type III glass beads provide brighter, longer lasting markings on airfields, increasing situational
awareness, safety, and cost effectiveness.
9