that weight was then divided by both the
paint’s density and the area of the panel
covered by paint.
Glass beads conforming to AASHTO
M 247, Type II and IV from Potters
Industries, Inc., were applied to the
painted lines of interest at a rate of 6
lbs and 12 lbs of beads per gal of paint,
respectively. Beads were applied from a
dispensing gun immediately following
the corresponding paint gun. Glass bead
dosages were determined by weighing a
panel striped with a bead embedded paint
film and subtracting out the already calibrated amount of paint on the panel.
Retroflectivity and Durability
Measurements
Within seven days of striping the lines
and approximately monthly thereafter,
for a period of 24 months, retroreflectivity was measured on each marking
in the skip-line and wheel track areas.
Retroreflectivity was measured using a
LTL2000 retroreflectometer (Delta Light
and Optics, Denmark), LTL-X retroreflectometer (Delta Light and Optics), or other
approved equivalent device exhibiting the
same geometric design criteria. The ratings
were averaged for replicate lines.
Durability assessments were made
near the skip-line and in the wheel tracks.
In the wheel tracks, an area covering nine
inches on either side of the wheel track
midpoint was examined and rated. The
durability rating was an assessment of the
percent of the marking remaining divided
by 10. For example, a line without any
notable wear receives a 10. Ratings were
averaged for replicate lines.
Abrasion Resistance
The abrasion resistance of the traffic mark-
ing paints was assessed following ASTM
D2486-96. Paint films were prepared on
a Leneta Form P-121-10N plastic chart
utilizing a 7, 15 or 30 mil drawdown bar.
Two paints were cast side-by-side with
one functioning as the control and the
other as the test film. After drying for one
week at 25˚ C and 50% relative humid-
ity the paint films were scrubbed utilizing
a Gardner Straight Line Washability and
Wear Abrasion machine equipped with
three brushes. The average number of
cycles to failure was reported.
To calculate the line’s thickness, the
weight of paint applied to the Leneta chart
was divided by both the paint’s density
and the area of the panel covered by paint.
Discussion
NTPEP Trials
The durability of the traffic marking paints
was assessed at numerous times through-
out the two year trial. Figure 1 illustrates
Figure 1: Transverse paint line on concrete after 10 months exposure.
Figure 2: Transverse paint line on concrete after 24 months exposure.
