Committee E17 defines skid resis-
The index allows highway profession-
E17 also covers data format require-
tance as "the ability of a traveled
als to compare roads internationally.
ments (E2560) for the profile-based
surface to prevent the loss of tire trac-
"Whether a fixed slip tester in the
systems as well as guidance for
tion (E867)," and a core E17 docu-
United States, a locked wheel tester in
m e a s u r i n g a n d r e p o r t i n g t h e
ment standardizes a familiar proce-
Saudi Arabia or a scrim, a side force
International Roughness Index
dure to check it. ASTM E274, Test
coefficient tester, in Germany, if we
(E1926).
Method for Skid Resistance of Paved
measure the texture in each location
Surfaces Using a Full-Scale Tire,
with the friction data then we can turn
Checking Runways
details how to measure pavement skid
all of the numbers into the same index,
As the U.S. space shuttles take their
resistance using a locked wheel tester
the International Friction Index," says
final flights this year, scientists and
and a special test tire. "E274 is a stan-
Frank Holt, vice president of business
engineers will check and recheck the
dard that defines the operation of that
d e v e l o p m e n t
f o r
D y n a t e s t
runways to measure friction and deter-
skid trailer," says Yager. "It's a device
International, Westland, Mich., an E17
mine runway condition. The proce-
that provides spot measurements of
member and former E17 chairman.
dures are based on such E17 stan-
friction at constant speed." The skid
Comparisons of friction results can
dards as E1859, Test Method for
trailer includes a hose and nozzle that
lead to better mix designs and
Friction Coefficient Measurements
lays down a stream of water in front of
reduced road maintenance costs.
Between Tire and Pavement Using a
a full scale rib (E501) or smooth
Variable Slip Technique, which
(E524) tire specified by such perfor-
The committee is also responsible for
utilizes a series of friction force
mance characteristics as tensile
standards that characterize the rough-
measurements of a braked test wheel
strength, modulus, specific gravity
ness of a road, which makes a differ-
as it is pulled over a pavement
and elongation.
ence in the comfort of a ride and ulti-
surface.
mately safety. "With a rough road, you
Information about pavement friction
can lose control," says Holt, who adds
Runway friction tests are taken within
from various testers together with
that the World Bank, headquartered in
3-5 m of its center, going up one side
surface texture measurements can
Washington, D.C., uses roughness as
and down the other, according to
then be compared using another E17
a factor in decisions about funding
Yager, so that the equipment software
standard: E1960, Practice for
pavement rehabilitation internation-
produces three values representing
Calculating International Friction
ally. One E17 test to measure rough-
each third of the runway. Pilots then
Index of a Pavement Surface, which
ness is E1274, Test Method for
know where rubber buildup exists due
was developed in the PIARC (World
Measuring Pavement Roughness
to previous landings. Yager says, "rub-
Road Association) International
Using a Profilograph, which calls for
ber buildup reduces the texture and
E x p e r i m e n t
t o
C o m p a r e
a n d
an articulated multi-wheeled device
hence the friction performance," and
H a r m o n i z e T e x t u r e a n d S k i d
that records road bumps over a speci-
pilots can plan landings according to
Resistance Measurements. Veteran
fied size. Another frequently refer-
the values from the ground vehicle fric-
ASTM and E17 member J.J. Henry,
enced roughness standard is
tion measurements.
Huntingdon, Pa., who was involved in
E950/E950M, which describes a stan-
the PIARC work, says that the index
dard approach for taking direct
Continuous reading tests such as
was developed to harmonize devices
measurements of elevation profile,
E2340, Test Method for Measuring the
that measure wet pavement friction.
which can then be used to estimate
Skid Resistance of Pavements and
The index consists of parameters that
roughness. E1364, Test Method for
Other Trafficked Surfaces Using a
report the calibrated wet friction and
Measuring Road Roughness by Static
Continuous Reading, Fixed-Slip
anticipated change in wet friction with
Level Method, focuses on direct
Technique, also provide a way to
speed, the speed constant of wet pave-
measurement of elevation profile and
record skid resistance along a track
ment friction.
is typically used to validate other
length and determine averages for
profile-based measurement methods.
specific test segments.
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Issue 70 September 2013 2013 70

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