Pavement Preservation Journal - Winter 2013 - (Page 35)
By Yetkin Yildirim, P.E.
he Texas Pavement Preservation Center
would like to thank the late Mr. Gary
Billiard for his years of service to the industry, and
hopes to honor his memory in endorsement of his
presentation on friction and texture enhancement which is
available for viewing online at the TPPC website (see News
Briefs, Fall 2013, p 29).
The Pavement Preservation Strategies: Friction Restoration
Conference was held at the Center for Transportation
Research in Austin. The workshop, which was jointly
sponsored by Skidabrader and TPPC, can be accessed on
the TPPC webpage under "conferences" (ww.utexas.edu/
These proceedings included presentations from direction
of the TPPC Dr. Yetkin Yildirim, Thomas Yager from
NASA Langley Research Center, and Mr. Billiard, former
president of Skidabrader.
Surface texture and friction are the main factors affecting
the safety of pavements. The friction force that develops
between the tire and pavement surface is an essential part of
the vehicle-pavement interaction; it gives the vehicle the ability
to stop safely. The greater the frictional resistance, the quicker
the vehicle can be slowed or stopped. Skid resistance is the
friction force which develops at the tire-pavement contact area.
Many factors influence the level of skid resistance on a
paved road such as: microtexture and macrotexture, age of
the road surface, seasonal variation, traffic intensity, aggregate
properties, and road geometry. The macrotexture of the
pavement surface is related to mixture design, compaction level,
as well as aggregate gradation. The microtexture is related to
the texture and shape characteristics of aggregates. Pavement
texture is defined as a road surface property that describes the
interaction between the road surface and vehicles tires.
When in a dry and clean state, roads generally provide
insignificant differences in friction levels, regardless the
type of pavement and surface configuration. Hence, the
operation on dry runway surfaces is mostly satisfactory.
Many studies have revealed that 15 to 18 percent of traffic
crashes occur on wet pavements. When in this state, the
water acts as a lubricant between the pavement surface and
the tires, which reduces friction. For this reason, most of the
equipment dealing with pavement friction measurement
operates in wet conditions.
Microtexture and macrotexture greatly influence the skid
resistance of road surfaces. Fig. 1 illustrates the difference
between microtexture and macrotexture. Adequate
macrotexture provides good drainage of water from the
pavement surface. Microtexture, on the other hand, provides
the direct contact between the tires and road surface and
contributes to the adhesion part of the pavement friction.
Pavement with rougher texture provides better skid
resistance; however, it may increase noise, vibration, and tire
Aggregate, being part of asphalt mixtures, plays a
major role when it comes to skid resistance. The aggregate
properties such as gradation, shape, and mineralogy dictate
its ability to resist polishing action by traffic. This ability to
resist polishing is the most significant characteristic to skid
resistance of pavement surfaces.
Hogervorst (1974) explained that skid resistance changes
with vehicle speed, and it depends on both microtexture and
macrotexture. The results of this study showed that the skid
resistance decreased as vehicle speed increased, and pavements
with a coarse and rough surface provided better skid resistance
compared to those with fine and polished surfaces.
Because of the great importance of pavement surface
skid resistance, many pieces of testing equipment are
developed and correlated to each other in order to measure
friction. The need for improvement of pavement friction
performance in existing roads has led to the development of
different treatments like shot-abrading, grooving, grinding,
and overlays. These topics were presented in more detail at
the Pavement Friction workshop which can be accessed on
the TPPC webpage.
Yildirim is director, Texas Pavement Preservation Center
Fig. 1: Microtexture and macrotexture greatly influence the skid resistance
of road surfaces
pavement preservation journal
Table of Contents for the Digital Edition of Pavement Preservation Journal - Winter 2013
NCPP Marks Decade as Voice of Pavement Preservation
Rocky Mountain West Partnership Honors Galehouse, Moulthrop
NCAT UPDATE: Eventful First Year for NCAT Preservation Group Study
Polymers Boost Performance of Conventional Fog Seals
Rare Double Fog Seal Among Techniques for Oklahoma Road
Florida Puts HIR Plus Virgin Overlay to Work on Tamiami Trail
ARRA, FHWA Sponsor In-Place Recycling Workshop and Demo
Problem Pavement Gets Permanent Patch
TPPC: Macrotexture and Microtexture Infl uence Pavement Safety
Wait Before First Slurry Seal Application
Index of Advertisers
Pavement Preservation Journal - Winter 2013