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Its just the study on skid resistance carried out in and around Bangalore, India on different types of pavement conditions. Its a brief study and not elaborate. It might just guide you in the right direction. Thank You.
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CHAPTER 1
INTRODUCTION
1.1 Background
Motor vehicle crashes are the third leading cause of death and the leading cause of
injuries in India. It is reported that in 2008 more than 1,35,000 people were killed and nearly
2.35 million were injured in crashes on the nation’s roadways of India (National Records Bureau,
2010). The consequences of traffic crashes are felt not only by those directly involved but also
by family members, friends, and coworkers who must deal with a devastating loss or find
resources to cope with disabling injuries. The costs to society such as lost productivity, property
damage, medical costs, emergency services, and travel delays are also tremendous. The World
Health Organization (WHO) reports that motor vehicle crashes worldwide kill 1.2 million and
injure 50 million people annually. The worldwide economic loss is estimated at $518 billion
each year (WHO, 2004). For these reasons improving safety is one of the primary goals of
transportation officials.
Pavement skid resistance is related to properties of both the vehicle tyre and the
pavement surface, and can be affected by volume and composition of the traffic load, available
tire tread depth and pattern, pavement temperature, the presence of water (rain), and other
pavement surface conditions.
Cross slopes have to be designed to provide adequate surface drainage and this is
considered a key measure to reduce hydroplaning occurrence. The design stopping distances are
determined based on assessments of the available pavement skid resistance, while speed limits
on highways have to take into consideration operational safety, i.e. skidding and hydroplaning.
Considering its importance, research on pavement skid resistance started since 1920s and most of
them mainly focused on two aspects, i.e. to measure and predict pavement dry and wet skid
resistance accurately, and to develop the strategies to increase skid resistance of wet pavements.
It is interesting to review two of the types of vehicular skidding one type of skidding is
when the wheels of a vehicle are locked by braking and cease to rotate, but the vehicle continues
to move. Another type is on horizontal curves when the vehicle moves at an angle to the intended
1
path. Skid resistance is the force at the tire-pavement interface which tends to keep the vehicle
from sliding. The measurement of this frictional resistance is called the coefficient of kinetic
friction.
Pavement skid resistance is primarily a function of the surface macrotexture and
microtexture. Macrotexture refers to the large irregularities on the road surface (coarse-scale
texture) that are associated with voids between aggregate particles. The magnitude of the
macrotexture depends on the size, shape, and distribution of coarse aggregates used in pavement
construction as well as the particular construction techniques used in the placement of the
pavement surface layer.
Microtexture refers to small irregularities on the pavement surface (fine-scale texture),
and it is related mostly to aggregate surface texture and the ability of the aggregate to maintain
this texture against the polishing action of traffic and environmental factors.
While a vehicle negotiates a horizontal curve, if the centrifugal force is greater than the
counteracting forces (i.e, lateral friction force and component of gravity due to super elevation),
lateral skidding takes place. The lateral skid is considered dangerous as the vehicle goes out of
control leading to an accident. The lateral skid resistance is generally equal to or slightly higher
than the longitudinal skid resistance in braking test.
The friction coefficient decreases with skid speed, which in turn depends on the speed of
vehicle and degree of brake application or the brake efficiency. The friction coefficient also
decreases slightly with increase in pavement temperature, tyre pressure and wheel.
Figure 1.1 Comparision of Micro-Texture and Macro-Texture
2
For the calculation of stopping distance, the longitudinal friction coefficient values of
0.35 to 0.40 have been recommended by the Indian Roads Congress, depending upon speed.
These values have been suggested keeping in view the minimum coefficient of friction in the
longitudinal direction on wet pavements and after allowing a suitable factor of safety, further
when a longitudinal friction coefficient of 0.40 is allowed for stopping the vehicle, the resultant
retardation is 3.93m/sec which is not too uncomfortable to the passengers. In the case of
horizontal curve design, the Indian Roads Congress has recommended the lateral friction
coefficient of 0.15. This low value of transverse skid resistance has been suggested considering
the worst possible surface condition such as mud on pavement surface at horizontal curve with
super elevation during the rains; us it is essential to prevent possible lateral skid, even under such
adverse pavement condition.
1.2 Need for present investigation
Through numerous investigations, the relationship between surface friction and roadway
safety has been recognized by transportation agencies and concern has grown with the number of
accidents occurring in wet pavement conditions. Several devices, from the simplest locked wheel
method to the more sophisticated trailers capable of measuring braking force over the entire
range of wheel slip, have been invented to measure skid resistance of road pavements or
runways.
However, the understanding of skid resistance mechanisms have not improved much over
the past century despite the improvements in the measurement techniques because it is hampered
by the lack of development in the theoretical, analytical or numerical models that can easily
explain and analyze skid resistance. This results in the reliance of empirical relationships in skid
resistance prediction.
It is still not possible to predict the traction performance of a tire-road system based on
the many tire and surface variables. Indeed, there is, as yet, no agreement as to how to quantify
many of these variables in a meaningful way. Hence the study was aimed at predicting the
relationship between portable skid resistance tester and dynamic skid resistance tester with
texture depth.
3
1.3 Objectives of present study
1). To conduct the Skid Resistance test on Dry, Wet & Mud on Pavement condition by using
Portable Pendulum Skid Resistance tester equipment.
2) .To conduct Skid Resistance test on Dry pavement by using Dynamic Trailer Type Skid
Resistance tester equipment.
3). To conduct Sand Patch method on pavements to measure the texture depth on different
stretches.
4). To Compare the values of texture depth and sampled portable skid values.
5). Comparision between skid resistance values for portable and dynamic skid resistance tester
for the test stretches.
4
CHAPTER 2
REVIEW OF LITERATURE
2.1 General
Traffic crashes and the associated injuries and fatalities remain a significant problem for
transportation professionals. The relationship between skid resistance and roadway safety has
long been recognized by transportation agencies and concern has grown with the number of
accidents occurring in wet pavement conditions. It is well documented that a pavement with high
skid resistance properties can be a significant factor in reducing the likelihood of a crash.
Inadequate skid resistance can lead to higher incidences of skid-related crashes.
Considering its importance, research on pavement skid resistance had started since 1920s
and most of them mainly focused on two aspects: to measure and predict wet pavement skid
resistance accurately, and to develop strategies to increase skid resistance of wet pavements.
Compared with the large amount of experiments and measurements on skid resistance, however,
understanding in skid resistance mechanism has not improved much over the past century
because it is hampered by the lack of development in the theoretical, analytical or numerical
models that can explain and analyze skid resistance. This results in the reliance of empirical
relationships in skid resistance prediction.
It is noted that it is still not possible to predict the traction performance of a tire-road
system based on the various tire and surface variables. Indeed, there is, as yet, no agreement as to
how to quantify many of these variables in a meaningful way. It is clear that there is a great deal
of definitive work yet to be done in this field.
Through numerous investigations, the relationship between surface friction and roadway
safety has been recognized by transportation agencies and concern has grown with the number of
accidents occurring in wet pavement conditions. NTSB and FHWA reports indicated that 13.5%
of fatal crashes and 18.8% of all crashes occur when pavements are wet (Dahir and Gramling
1990). It is well documented that a pavement with high skid resistance properties can be a
significant factor in reducing the likelihood of a crash.
5
Inadequate skid resistance can lead to higher incidences of skid-related crashes. Hosking
(1987) reported that an improvement in the average skid resistance level of 10% could result in a
13% reduction in wet skid rates. These studies show the importance of adequate frictional
characteristics between the tire and pavement surface and its associated reduction in the risk of
hydroplaning occurrences.
Cross slopes have to be designed to provide adequate surface drainage and this is
considered a key measure to reduce hydroplaning occurrence (AASHTO, 2004; Wolshon, 2004).
The design stopping distances are determined based on assessments of the available pavement
skid resistance, while speed limits on highways have to take into consideration operational
safety, i.e. skidding and hydroplaning (Lamm et al., 1999).
Up to date, modern theories still cannot grasp the complex mechanism due to their
dependence on empirical constants obtained from experiment. The contact area and adhesion
mechanism between the moving rubber tire and pavement is hard to obtain. The lubrication
theories and rubber constitutive modeling result in non-linear partial differential equations where
the solutions could not be obtained analytically.
However, with the development of computing power, researchers can employ the
numerical model to simulate the complex phenomenon. It is feasible to establish a more complex
finite element model considering tire-fluid-pavement interactions so as to gain a better
understanding of the skid resistance and hydroplaning and to offer new perspectives to the skid
resistance problem.
2.2 Skid Resistance
Skid resistance is the opposing force developed at the tire-pavement contact area. In other
words, skid resistance is the force that resists the tire sliding on pavement surfaces. It is a
measure of the ability of pavement to resist the skidding of a tire and an essential component of
traffic safety to maintain vehicle control and reduce the stopping distance in emergency braking
situations.
Skidding occurs when the frictional demand exceeds the available friction force at the
interface between a tire and pavement (Kennedy et al. 1990). Numerous factors can influence the
6
magnitude of the skid resistance generated between the tire and pavement surface. These factors
include characteristics of pavement surface (microtexture and macrotexture), tread depth and
patterns, groove width, construction material and inflation pressure of tires, presence of
contaminant, vehicle speed and so forth.
Skid Number (SN): Friction always involves two bodies. It is even imprecise to say that
a particular tyre on a given pavement produces a certain friction factor, unless forward or sliding
speed, inflation pressure, load, temperature, water-film thickness and other details are specified.
To overcome the resulting communication-problem standards have been developed that prescribe
all variables that influence the friction factor. SN = 100 f = 100 F/L
F is obtained in a strictly defined manner by sliding, a lucked, standardized tyre at a
constant speed (usually 40 mph) along an artificially wetted pavement. The term skid number (or
SN) should not be used in connection with any other skid resistance measurements except those
made at the same speed in accordance with ASTM E 274.
Slip occurs when a wheel, revolves more than the corresponding longitudinal movement
along the road. Slipping usually takes place in the driving wheels of a vehicle when the vehicle
rapidly accelerates from Stationary position or from slow speed on pavement surface which is
either slippery and wet or when the road surface is covered with loose material such as mud.
2.3 Mechanism of Skid resistance
Skid resistance developed between tire and pavement surface has two major components:
adhesion and hysteresis. In the dry case the mechanism of molecular-kinetic bonding is most
widespread due to the maximum interfacial area. However, upon wetting, the interfacial film of
fluid is spread uniformly and this effectively suppresses the electrical roughness of the surface,
thereby reducing the adhesion component to a very low value (Moore, 1972).
If the road surface has a high macrotexture, the voids in the asperities can act as
reservoirs for the fluid and the pressure distribution at each asperity summit promotes local
drainage. Thus, some adhesion under wet condition for a pavement with good macrotexture will
still exist to provide friction.
7
Adhesion
The adhesion component of skid resistance indicates the shear force which develops at
the tire-pavement interface as the tire conforms to the shape of the contact area (Choubane et al.
2003). It is due to the actual contact between the rubber tire and the pavement and results from
the shearing of molecular bonds formed when the tread rubber is pressed into close contact with
pavement surface particles (Panagouli and Kokkalis, 1998).
It has been noted that the adhesion component is reduced when particles or water film are
present at the contact surface (Roberts, 1992; Person, 1998) and will disappear if the surface is
completely covered by a lubricant. It is believed that the adhesion component of skid resistance
is governed by the microtexture of pavements (Priyantha and Gary, 1995).
On wet pavements, the intimate contact remains by breaking through the thin water film
even after the bulk of water has been displaced. However, the manner in which microtexture is
effective is complex because it affects the molecular and electric interaction between the
contacting surfaces (Kummer, 1966). The adhesion component is dependent of vehicle speed and
is dominant at low speeds (Moore, 1972). In the low speed range, the microtexture ensures
physical penetration of the interface squeeze-film so that good adhesion is obtained.
Hysteresis
The hysteresis component of skid resistance is related to the energy storage and
dissipation as the tire rubber is deformed when passing across the asperities of a rough surface
pavement. The hysteresis component typically becomes dominant after the tire begins to skid. At
that moment, the adhesion component, which is dominant prior to a skidding condition, begins to
decrease and the hysteresis component undergoes a corresponding increase (Choubane et al.
2003).
The hysteresis contribution usually is fairly independent of speed in the range in which
highway tires are likely to slide. Thus it gains in importance at higher speeds when adhesion
component decreases (Moore, 1969). Although both microtexture and macrotexture have effect
on the hysteresis friction, it is believed that the magnitude is mainly controlled by the
macrotexture of pavement surface (Priyantha and Gary, 1995).
8
2.4 Factors affecting Skid Resistance
2.4.1 Properties of aggregates
Surface Texture
Microtexture and macrotexture are the two levels of pavement texture which affect the
friction between the pavement and tire, as depicted in Figure 2.1. Microtexture refers to
irregularities in the surfaces of the stone particles (fine-scale texture) that affect adhesion. It has
the function of preventing the formation of a thin, viscous, lubrication film of water between the
tire and road.
A harsh microtexture provides a high level of friction, but a surface having a smooth,
polished microtexture will give poor friction even at low speeds (Leland and Taylor, 1965).
Microtexture and adhesion contribute to skid resistance at all speeds especially at speeds less
than 30 mph (48km/h).
Macrotexture refers to the larger irregularities in the road surface (coarse-scale texture)
that affect hysteresis. Macrotexture has the primary function of providing drainage channels for
water trapped between the tire and road. Surfaces having rough macrotexture show a less rapid
decrease of friction with increasing speed than do surfaces having smooth macrotexture (Sabey,
1966), as shown in Figure 2.3. Macrotexture and hysteresis are less critical at low speeds;
however, as speeds increase a coarse macrotexture is very desirable for wet weather travel.
Figure 2.1 Comparison between Microtexture and Macrotexture (Flintsch et al., 2003)
9
`
Figure 2.2 Comparison between Textured surfaces (Flintsch et al., 2003)
Size & Shape of aggregates
Aggregate Shape: Aggregate shape depends on many of the same factors that influence
its texture. These include hardness of grains, strength of matrix, and overall resistance of the
aggregates to abrasion.
Size and Gradation of Aggregates: In bituminous surface, generally larger size
aggregates have greater control over the skid resistance than the smaller size aggregates. In
cement concrete pavements, however, the sand-size aggregates control the skid resistance
performance of the pavement surface. Aggregate size is controlled by the grading requirements.
Petrology
It has been observed that aggregates undergo polishing effect with passage of traffic.
These exhibit varying degree of polishing characteristics, depending mainly on petrology, the
differential polishing characteristics of the mineral constituents are mainly responsible for this
10
phenomenon. An optimum blend of hard and soft material in the rock has been observed to yield
high skid resistance properties.
Resistance to Polishing: The ability of an aggregate to resist the polish-wear action of
traffic has long been recognized as a most important characteristic. When an aggregate becomes
smooth it will have poor skid resistance. Also if it wears and polishes too rapidly, the pavement
will lose its texture and become slippery when wet. The polish-wear characteristics of an
aggregate is not readily predictable from its physical and chemical makeup.
Lime-stone is found to get polished rapidly and causes slipperiness of the surface. This
effect of polishing is due to the amount of acid insoluble material present in the lime-stone.
Higher the amount of acid insoluble material lesser is the polishing rate and so higher is the skid
resistance. This is due to the reason that impurities wear less rapidly than the pure carbonate,
thus presenting a surface favorable lo antiskid properties.
The rate of polishing depends on the hardness of the grains, die frequency of contact by
the traffic and the media (such as dust and grime) on the roadway surface. For an aggregate to
exhibit satisfactory skid resistance properties, it probably should contain at least two mineral
constituents of different hardness in order to wear differentially and expose new surfaces.
2.4.2 Nature of Surfacing
With a few exceptions, all types of new surfacing are capable of attaining a high skid
resistance in wet weather. On the other hand, under adverse conditions such as heavy traffic, age
and poor quality control and improper mix design, low values of skid resistance may be obtained
on most surfacing.
2.4.3 Presence of Water on pavement Surface
Adhesion between the tyre and the road surface in a dry condition is sufficiently high, but
it drops down steeply as the road surface becomes wet. It steadily drops until a certain water rate
is reached and the reduction in skid resistance at this stage can be of the order of 50 percent. The
phenomenon of reduction of skid resistance on wetting can be explained in simple terms that the
water film lubricates the tyre-pavement interface and causes reduction in the frictional resistance.
11
2.4.4 Other materials on Pavement Surface
Rubber, oil, and accumulated oil spillage are some of the more common contaminants
that are found on roadways. When contamination, such as a thin film of oil or water, is present,
the tire-pavement interface will be lubricated, thus reducing tire-pavement friction significantly
(Irick, 1972). It has been noticed that even a very small amount of water can cause a large
decrease in friction coefficient, especially on surfaces having a polished microtexture (Leland
and Yager, 1968).
2.4.5 Vehicle Factors
Vehicle factors affecting skid resistance include tire inflation pressure, tire temperature,
tread pattern, tread depth, wheel load, and vehicle speed. These factors contribute to the level of
strength in the interaction generated between the tire and the pavement. In general, friction
decreases with speed increasing, while increases as tire pressure and wheel loads increasing,
particularly on wet pavements. It is reported that both peak and locked wheel braking force
coefficients decrease with increasing speed on the wet pavements. However, the locked wheel
value usually decreases more rapidly than does the peak value.
Figure 2.3 Effect of speed on wet pavement skid friction (McLean and Foley, 1998)
12
Tire treads are another important factor. After the tread is worn away, tires develop more
friction on dry pavements because more rubber comes into contact with the pavement. However,
when the pavement becomes wet, the friction diminishes with tread wear because the tire cannot
expel water from the contact area through the treads. In addition, the types of tires also have
significant influence on skid resistance. Truck tires generally have remarkably lower skid
resistance compared with car tires.
2.5 Methods of measurement of skid resistance
2.5.1 Passenger car braking tests
In this test, the wheels of the test vehicle are locked at a given speed and the behavior of
sliding vehicle is observed. A certain length of roadway which is blocked for other movement of
traffic is used. The test vehicle is brought upto the required speed and the tyres of this vehicle is
allowed to roll for a short distance so that it becomes thouroughly wet. When the test vehicle are
locked the vehicle slides to stop. The main disadvantage of this test is that it is dangerous to
perform these tests on wet pavements at high speeds.
2.5.2 Deceleration test
Figure 2.4 Forces developed when a passenger car is braked
13
When a passenger car is braked the total weight of the vehicle which is acting through the
center of gravity is counter acted by the normal forces at the front and rear of the wheels. A
decelerometer which could be fitted to test vehicle consists of damped pendulum unit which is
rigidly mounted to the frame of the test vehicle. As the brake is applied, the rate of deceleration
appears on a dial and may be read along with vehicle speed.
2.5.3 Variable Slip Devices
Variable slip devices measure the frictional force as the tire is taken through a
predetermined set of slip ratios (Henry 2000). ASTM Standard K 1859 outlines the full
procedure for measuring pavement friction using a variable slip technique. The slip friction
number (SFN is a measurement of the longitudinal frictional force divided by the vertical force
on the test tire (ASTM F 1859). The SFN is recorded over a range of slip speeds from zero up to
the test speed and the results are presented in a graphical format.
2.5.4 Locked-Wheel Devices
The most common method for measuring pavement friction in the United States is the
locked-wheel method (Henry, 2000). The locked-wheel method is specified in ASTM E 274.
This method is meant to test the frictional properties of the surface under emergency braking
conditions for a vehicle without anti-lock brakes.
Figure 2.5 Locked Wheel Trailer Type Skid Resistance Tester
14
As opposed to the side force and fixed slip methods, the locked-wheel approach tests at a
slip speed equal to the vehicle speed, this means that the wheel is locked and unable to rotate
(Henry 1986). The results of a locked-wheel test conducted under ASTM specifications are
reported as a skid number (SN) or friction number (I N), liquation (4) is used for computing SN
or FN.
2.5.5 Accelerated Polishing Test
The purpose of this test is to give a relative measure of the degree of polishing of
aggregates under traffic condition (Shahin, 1994). The test consist of two separate steps, the first
is the accelerated polishing machine and secondly by the pendulum skid tester. Figure 2.5 shows
the accelerated polishing machine.
Figure 2.6 Accelerated polishing machine (BSI, 1990)
The accelerated polishing machine has a road wheel with a flat periphery (45mm wide
and 406 mm in diameter) and of such a size and shape that 14 specimens can be clamped around
the periphery so as to form a continuous surface of aggregate particles. The wheel is rotated
15
about its axis at a speed of 315 to 325 rev/min (Shahin, 1994). The first 3 hours, water and corn
emery grits are fed continuously onto the surface of the specimens. The machine and the
specimen are washed thoroughly and then continue for another 3 hours but fed with water and
air-floated emery flour. The specimen are then removed from the machine and tested using the
portable skid resistance tester.
2.5.6 British Pendulum Tester
The BPT is one of the stationary types of skid testers. It comprises a support frame that
can be leveled on the road. Attached to the support frame is a swinging arm, at the bottom of
which is an ASTM1 rubber measuring foot. This swinging arm, when released.
The British pendulum tester is a dynamic impact device used to measure the energy loss
when a pendulum with a rubber slider contacts a test surface located tangentially to the arc of the
pendulum swing. A standard procedure for use of the British pendulum tester is given in ASTM
E 303-74 [31]. The tester provides a reading called the British pendulum number BPN, which is
generally accepted as an indirect measure of pavement micro texture.
Figure 2.7 Pendulum Skid Resistance Tester (BSI, 1990)
16
2.5.7 Dynamic Skid Resistance Tester
Various types of trailer type or towed vehicle skid resistance testing equipment have been
developed .by various organizations/institutions. The Equipment consists of trailer unit and load
measuring devices. The trailer unit is to be towed by a tractor unit which may be a Jeep or any
other automobile. The two wheeled trailer unit for skid resistance testing is attached to the tractor
unit through the load measuring equipment with the help of suitable attachments.
The skid resistance of the pavement surface is measured by locking the wheels of the trailer unit
and dragging it over the test. The ends of the axle are attached to the chassis frame through a pair
of leaf springs. The chassis is made of tubular frame using I.S. pipes.
The chassis is attached to balast frame with vertical supports. The overall dimension of the frame
is resting over the wheel axle assembly. In order to pull the trailer V-shaped arm made of 25mm
diameter S pipes of length 75 cms each is attached to the chassis frame. The other end of the V-
arm houses through which a 20 mm latch.
A suitable connecting device is screwed to the end of this rod to enable the trailer unit to be
connected to the towing vehicle with special bracket and chain assembly. A suitable attachment
has been housed on the frame between the V-arm and the chassis to house the load cell. The
details of the attachment consist of a base plate and two vertical supports with elongated holes.
The load measuring device is an electrical load cell of 500kg capacity and is housed in this
assembly such that the direct pull is transmitted to the load cell and the cell is not damaged due
to torque's and due to the lateral forces acting during transverse oscillations of the trailer unit and
while turning. An auxiliary arrangement for measuring the load by means of another load cell of
250kg capacity is used. The wheels have been attached with hydraulic braking system consisting
of master cylinder.
2.6 Works done on Skid Resistance
2.6.1 Predicting Asphalt Mixture Skid Resistance Based On Aggregate Characteristics
Eyad Masad, Arash Rezaei, Arif Chowdhury, and Pat Harris., 2009 conducted a study to
develop a method to determine the skid resistance of an asphalt mixture based on aggregate
17
characteristics and gradation. Asphalt mixture slabs with different combinations of aggregate
sources and mixture designs were fabricated in the laboratory, and their skid resistance was
measured after different polishing intervals. Frictional characteristics of each slab were measured
by sand patch method, British Pendulum, Dynamic Friction Tester (DFT), and Circular Texture
Meter (CTMeter). The results of the analysis confirmed a strong relationship between mix
frictional properties and aggregate properties. The analysis has led to the development of a
model for the International Friction Index (IFI) of asphalt mixtures as a function of polishing
cycles.
2.6.2 Analysis of the Seasonal and Short-Term Variation of Road Pavement Skid
Resistance
Study was undertaken by Douglas James Wilson et al., 2006 regarding regular field
monitoring using the GripTester and the Dynamic Friction Tester measurement was carried out
on seven sites in the Auckland and Northland Regions of New Zealand was undertaken over a
three year period. The effects of temperature, rainfall, contaminants, new surfacings, geometric
elements and aggregate properties were analyzed to investigate factors that initiate changes in the
measured skid resistance of pavement surfacings.
The results have demonstrated that significant and previously unpredictable variations
(greater than 30%) in measured skid resistance can occur over short time periods. These
variations cannot be explained by any one factor. They are the result of a number of inter-related
factors, including the geological properties of the aggregates and the contaminants themselves,
the previous rainfall history, the road geometry, the calendar month of the year and depending
upon the measurement device, the temperature during testing.
2.6.3 Precision of Locked Wheel Testers for Measurement of Roadway Surface Friction
Characteristics
Bouzid Choubane, Charles R. Holzschuher, Salil Gokhale, 2003 conducted a field study
to assess the level of precision of its own locked-wheel testers for field measurements. Friction
measurements were acquired using four friction locked-wheel testers concurrently on a number
of asphalt section sites. The collected friction data was first analyzed to determine the friction
characteristics at each test location, in terms of a friction number at 40 mph using a standard
18
ribbed test tire. The primary objective of this study was to assess the precision of locked-wheel
testers for determining the friction characteristics of roadway surfaces in Florida in accordance
with ASTM2E-274, Standard Test Method for Skid Resistance of Paved Surfaces Using a Full-
Scale Tire. The precision of these units was addressed in terms of testing repeatability and
reproducibility.
2.6.4 Evaluation of Tire Skid Resistance on Contaminated Wet Pavements
W. R. Tyfour et al., 2008 has designed, fabricated, and used an experimental test rig to
study the effect of wet pavement contamination on the tire-pavement skid resistance. Results
showed that although precipitation water reduces tire-pavement skid resistance, the presence of
other contaminants plays a major role in further loss of this resistance. It has also been shown
that the fractional constituents of pavement contaminants vary according to the vertical profile of
the same road under the same traffic density.
The skid resistance on a contaminated up-gradient was found to be lower than that of a
contaminated down-gradient of the same traffic density. Among other contaminants, rubber
particulates produced by tire wear appear to have minimal effect on the loss of tire-pavement
skid resistance.
2.6.5 Evaluation of Field Performance of High Friction Surfaces
Edgar de Len Izeppi & Kevin K. McGhee, 2006 describes an evaluation of high friction
surface (HFS) systems. The goal of this evaluation was to develop guidance for agencies when
considering whether an HFS was an appropriate solution when addressing specific instances of
low skid resistance and/or especially high friction demand. Study also seeks to learn enough
about the special characteristics of common HFS options to be able to match alternatives with
appropriate location and application.
2.6.6 Evaluating the effect of crushing on the Skid Resistance of Chipseal Roads
R. Henderson, G. Cook, P. Cenek, J. Patrick, S. Potter 2005 , checked the level of
allowabilty of more effective utilization of road surfacing aggregate by better understanding how
aggregate shape and texture affect skid resistance. It was found that Skid resistance increases
linearly with percentage crushing. For new and unpolished aggregate, the increase in BPN in
19
going from 0% crushed chips to 100% crushed chips is approximately 25%. Also Skid resistance
increases with crushing by two mechanisms ie., the microtexture of crushed faces is greater than
the microtexture of uncrushed faces (after Accelerated Polishing Machine (APM) polishing, the
increase in PSV of crushed faces compared with uncrushed faces is approximately 4.5 PSV units
and it was found that new and unpolished crushed chips are more ‘angular’ in shape than
uncrushed chips, but for heavily polished surfaces where sharp chip edges have become rounded,
the increase in BPN due to chip shape in going from 0% crushed chips to 100% crushed chips is
estimated as negligible.
2.6.7 Measurment of Skid Resistance and Durability of Coated and Uncoated Concrete
Floors in Dairy Cattle Buildings
In order to evaluate walking areas of cattle buildings and their grip or skid resistance,
Heiko Georg, 2008 measured with a Skid Resistance Tester to obtain SRT-values were
performed on several dairy farms in Germany.
Uncoated concrete, brushed concrete, epoxy resin coating and mastic asphalt as coating
of concrete were investigated. Results demonstrated, that even high quality concrete had low
SRT-values and thus low grip, whereas mastic asphalt showed high SRT-values, meaning good
grip. Processing uncoated concrete surface and epoxy resin coating lead to higher SRT-values
compared to mastic asphalt.
2.6.8 Aggregate Resistance to Polishing and its Relationship to Skid Resistance,
Study were conducted by Arif Chowdhury, Tom Freeman, Arash Rezaei, to establish the
present state of knowledge in the area of skid resistance models, techniques for measuring skid
resistance, and methods for measuring aggregate frictional characteristics. The surface treatments
had a very high variability in skid number. PFC mixes exhibited better skid resistance and lowest
variation than other mix types.
There was high interaction between aggregate characteristics, mixture types, and traffic
levels (polishing due to traffic). In general, it is hard to classify aggregates without specifying
mixture type and traffic levels. Skid resistance depends on micro-texture, macro-texture, and
20
polishing susceptibility of the aggregates. This is why some aggregate types performed poorly in
certain mixtures, while their performance was acceptable in other mixtures.
2.6.9 Skid Resistance and Hydroplaning analysis of Rib Truck Tires
Cao Changyong, et al., 2009 conducted studies to investigate the skid resistance and
hydroplaning performance of rib truck tires including wide-base truck tire by using a dynamic
friction tester and British Pendulum Tester. The slip speed for BPT is very low (6 mph or 10
km/h) and as a result British Pendulum (BPN) is typically used as a surrogate for pavement
microtexture. it only provides a measurement for the friction at very low speeds and that the
values of BPN do not correlate well with the frictional properties measured using other devices.
It has been noted that the adhesion component is reduced when particles or water film are
present at the contact surface (Roberts, 1992; Person, 1998) and will disappear if the surface is
completely covered by a lubricant. It is believed that the adhesion component of skid resistance
is governed by the microtexture of pavements (Priyantha and Gary, 1995).
On wet pavements, the intimate contact remains by breaking through the thin water film
even after the bulk of water has been displaced. However, the manner in which microtexture is
effective is complex because it affects the molecular and electric interaction between the
contacting surfaces (Kummer, 1966). The adhesion component is dependent of vehicle speed and
is dominant at low speeds (Moore, 1972). In the low speed range, the microtexture ensures
physical penetration of the interface squeeze-film so that good adhesion is obtained.
2.6.10 Evaluation of various Friction measurement methods and the correlation between
road friction and traffic safety
The aim of the project conducted by Carl-Gustaf Wallman , Henrik Åström, was to gather
information about the different friction methods in use and about published quantitative relations
between road friction and accident risk. Regarding friction measurements, every country has
instruments and methods of its own, and the friction values reported from different international
investigations are therefore not directly comparable.
21
2.6.11 Measurement of Non-Contact Skid Resistance using Locked Wheel Skid Trailer
(ASTM- E 274) 15 Dynamic Friction Tester (DFT) (ASTM E-1911) 15 & Sideway-force
Coefficient Routine Investigation Machine (BS 7941-1:2006)
Dr. Jay N. Meegoda et al., 2009 presented a mechanistic explanation and a correlation
between skid number (SN40R) and Mean Profile Depth (MPD) for asphalt pavements. They
were proposed based on texture data collected from high speed laser for five new asphalt
pavements. The comparison of data between old and new asphalt pavements is also presented in
this manuscript. The result shows that the trend of correlation for old asphalt pavements is
similar to that of new asphalt pavements.
The proposed correlation and the PMS interface will be used by the NJDOT to screen all the
roadway pavements belonging to the state of New Jersey using high speed laser and the
predicted skid numbers will be included in the NJDOT Pavement Management Database. Hence
with the predicted skid numbers NJDOT could reduce the use of expensive locked wheel skid
testers saving thousands of taxpayer dollars.
2.6.12 Evaluation of International Friction Index and High friction Surfaces
Julio Alberto Roa, 2008 studied some of the HFS systems available by measuring their
performance in different applications, under different weather conditions, and in various
locations, Compare friction measuring results made with different devices & evaluate if available
harmonization adopted models are valid.
The results of the evaluation of the various identified HFS products and applications
suggested that HFS are an appealing alternative for areas with frequent wet weather and/or run‐off‐the‐road crashes. Therefore, HFS systems should continue to be considered in the pool of
available safety improvement alternates. Additional application and before and after crash
studies for different application conditions may provide additional understanding of the benefits
of the various available systems.
The use of recorded accident data on black spots where friction is being monitored
frequently is recommended to determine required threshold levels for surface properties’
maintenance and rehabilitation. The existing correlation between accidents, skid resistance and
22
geometric design parameters, like radius of curvature, could be further studied, for the reason
that a high percentage of accidents occur on curves.
2.6.13 Friction Testing of Pavement Preservation Treatments for Temperature Corrections
and Operator/Machine Variability
Bruce Steven, University of California Pavement Research Center carried out tests to
develop, if possible, a correlation between friction values measured using CTM 342 and the BPT
together with its level of significance, development of a new temperature correction relationship
for the BPT to account for the significantly higher pavement temperatures experienced in
California during BPT testing (up to 45°C); and evaluation of the variability of the BPN
resulting from different operators, BPT devices, slider pad wear, and pavement temperature.
The British standard for British Pendulum Tester (BPT) measurements requires the use
of a temperature correction factor for test temperatures outside the range of 17°C to 22°C; the
ASTM standard does not specify a temperature correction. Based on the results presented it can
be concluded that there is no appreciable difference in the BPN20 results obtained by either
suitably trained and experienced operators or the results obtained from slider pads that are within
the material, age, and level-of-wear specifications. There was small bias between the two
instruments that were used; however, the bias was small (0.5 BPN20 units) and within the
repeatability limits that were found in this investigation.
23
CHAPTER 3
PRESENT INVESTIGATION
3.1 General
Skid resistance measurement and analysis is now a routine procedure in motor vehicle
crash analysis. Many different measurement methods are in common use, including visual
estimation assisted by friction tables; various dragged devices with friction force measurement
and instrumented vehicle skid-to-rest testing, the last having become the preferred alternative for
many investigators over the past decade.
Over the years, tyre manufacturers have done a lot of research into different types of
rubber and tread patterns to improve the safety of motor vehicles Highway engineers have also
researched ways to improve the skid resistance of road surfaces. The impetus for this research
came from the Transport and Road Research Laboratory (TRRL) of UK. One of the first things
they did was to devise the Pendulum Skid Tester which, being portable, can be taken to the site
or used in laboratory experiments. This device simulates the skid resistance offered by a road
surface to a motor car travelling at 50 km/h. It gives a number, being a percentage, somewhat
akin to a coefficient of friction. Subsequently, they devised the Sideways Force Coefficient
Routine Investigation Machine (SCRIM).
The interpretation and analysis of the results obtained by skid resistance measurement in
the forensic context may seem to be an obvious process but it is not always straightforward.
Uncertainties exist and there is considerable scope for fundamental error. Hence a comparative
study was made between the dynamic skid tester and the portable pendulum tester to correlate
their values.
3.2 Tests conducted
1). Measurement of Skid Resistance using Dynamic Skid Resistance Tester (ASTM E 274)
2). Measurement of Skid Resistance using Portable Skid Resistance Tester (ASTM E 303)
3). Measurement of Texture Depth (TRRL 1969)
24
3.3 Portable Skid Resistance Tester
Skid resistance tests are conducted on wet surfaces and produce a coefficient of friction
measured by a portable skid resistance tester. The device consists of a pendulum with a rubber
pad fixed to the lower end, and a graduated scale. The device is operated by swinging the
pendulum through a standard distance such that the rubber pad touches the surface to be tested,
reducing the pendulum's inertia as it completes the arc. A light pointer indicates the peak of the
first swing, which is measured against the graduated scale giving the coefficient of friction of the
surface tested. The result expressed as a decimal fraction which when multiplied by a hundred
gives the skidding resistance of the surface. To obtain adequate results the test should be
repeated to obtain a minimum of three results or until there are at least three consecutive
consistent readings.
Figure 3.1 Portable Skid Resistance Tester
3.3.1 Test procedure
1). First the portable pendulum type skid resistance tester is placed on the pavement surface at
the test spot.
2). The swing of the pendulum was kept parallel and in the direction of traffic.
3). The base plate is leveled by using foot screws and spirit level.
25
4). The indicator is adjusted to indicate zero when the pendulum is allowed to swing freely.
5). The height of the pendulum is adjusted such that the skid is equal to the standard length
(127mm) measured by means of a reference scale and the position of the hinge is fixed by
tightening the fixing knob.
6). The pendulum is raised to the horizontal position and is held by the catch, the pointer is
brought to vertical position.
7). The pendulum is then released allowing the tire specimen fixed with shoe of the pendulum
hammer slides over the pavement surface and the pendulum swings upwards leaving the dead
pointer at the highest position.
8). The angle or skid number read on the calibrated circular scale indicated by red pointer.
9). The pendulum is held by hand when it swings back before the shoe strikes the ground again.
10). The test is repeated three times at every test spot to get consistent readings and the average
at the three values was taken as the skid resistance of that test spot.
11). The angle obtained is converted to skid resistance based on the concept that,
Loss in kinetic energy = Amount of work done
W*H*tan θ = R*f*L
Where,
W- Total weight of the pendulum, kgs
H- Distance of shoe of tester from centre of rotation, cms
θ- Angle of Swing
R- Reaction of the shoe of the tester, kgs
f- Coefficient of friction
L- Skid length, cms
26
12). The test was repeated at the same spot after applying water and wetting the pavement
surface to determine the wet skid resistance values.
Figure 3.2 Graduated Scale with swing indicator
Figure 3.3 Water on Pavement Condition
27
The quantity measured with the portable tester has been termed "Skid-resistance" and this
correlates with the performance of a vehicle with patterned tires braking with locked wheels on a
wet road at 50 km/h.
3.4 Measurement of Texture Depth by Sand Patch Method
3.4.1 Test Procedure
1). Before starting the work, the road traffic is diverted away from the test sections.
2). Along the selected wheel paths points are selected to measure macro texture depth. These
points are suitably marked for easy identification, cracked spots are avoided.
3). Before the sand is spread, the testing point is cleaned with a brush to remove any dust are dirt
present in the voids.
4). Known quantity of sand (200gms) passing 300 micron and retained on 150 micron sieve is
poured on the pavement surface and it is evenly spread to fill the depressions of the pavement
surface and the sand is spread in a circular shape.
5). The average diameter of the circular patch is measured.
6). From the measured average diameter and known volume of sand used, we can find out the
texture depth by using the relation
Texture Depth=Volume of Sand ÷ Area of Sand
7). The same procedure is repeated for the other points in the test section and average texture
depth is calculated.
28
3.5 Measurement of Skid Resistance using Dynamic Skid Resistance Tester
Trailer Unit
The trailer unit is fixed in the special bracket of the towing vehicle (Sumo) with a bolt &
nut. The load cell is fixed to a plate in between two guides provided. A steel wire rope from the
bottom end of the dynomometer passes through the pulley and is connected to one end of the
load cell. The pull is applied in a horizontal direction. The wire rope is clamped at by C-clamps.
Provision has been made for fixing both the load cell and dynomometer .The brake
master cylinder of the trailer is fixed in the towing vehicle in such a position that the brakes of
the trailer could be applied conveniently from the test seat on the towing vehicle.
The 12 volts DC storage battery is placed on the towing vehicle to supply power to the
digital display unit. The display unit is connected to the battery and switched on. Now the
dynamic skid resistance testing units are ready for the tests. The total normal load on the two
wheels of the trailer W is found to be 240kgs.
Figure 3.4 Load Cell Assembly with Guide Rods
29
Figure 3.5 Trailer Unit Connected to the Towing Vehicle
Test Procedure
1). The towing vehicle with the trailer unit attached is moved on the test section at uniform speed
and the initial load reading P1kg of the load cell is noted on the laptop.
2). The brake pedal is pressed hard with the foot so as to fully lock the wheels of the trailer unit
and allowed to skid over the test surface at the uniform speed. During the application of brakes
the two wheels of the trailer are checked, whether they are uniformly locked; if not the brake
shoes are adjusted until both the wheels are equally locked simultaneously on- applying the
brakes.
3). Now the load reading, P2 kg of the load cell is recorded in the laptop along with the rpm of
the wheel. The average speed of the towing vehicle during the load readings P1 and P2 may also
be recorded.
4). The difference between the two load readings i.e., (P2-P1) kgs gives the total frictional force
offered by the pavement surface against the skidding trailer wheels.
f= P2−P1W
= P2−P1240
30
Figure 3.6 Skid marks on the test stretch
Figure 3.7 Trailer along with the towing vehicle
31
CHAPTER 4
ANALYSIS OF DATA
Skid resistance studies are conducted on five different identified stretches using Dynamic
Trailer Type Skid Resistance Tester and portable pendulum tester equipment and also sand patch
method was conducted to find the texture depth on this straight stretches namely
1). Nagadevanahalli Arch
2). Dodda Basti Road
3). Komghatta Road
4). GSSIT College Road
Table 1.1 Mean skid resistance values on Nagadevanahalli Arch
Stretch Location
Mean Skid
Resistance
On Wet
Pavement
Mean Skid
Resistance
On Mud
Pavement
Mean Skid
Resistance
On Dry
Pavement
Mean
Texture
Depth
Nagadevanahall
i Arch
NA1 0.56 0.43 0.81 0.56
NA2 0.58 0.41 0.68 0.59
NA3 0.57 0.47 0.79 0.7
NA4 0.63 0.32 0.77 0.65
NA5 0.49 0.49 0.67 0.68
NA6 0.57 0.42 0.69 0.63
NA7 0.6 0.44 0.72 0.52
NA8 0.64 0.44 0.78 0.59
NA9 0.6 0.45 0.72 0.66
NA10 0.54 0.43 0.7 0.7
32
Table 1.2 Mean skid resistance values on Dodda Basti Road
Stretch Location
Mean Skid
Resistance
On Wet
Pavement
Mean Skid
Resistance
On Mud
Pavement
Mean Skid
Resistance
On Dry
Pavement
Mean
Texture
Depth
Dodda Basti
Road
DB1 0.47 0.7 0.65 0.67
DB2 0.48 0.64 0.61 0.61
DB3 0.38 0.51 0.56 0.56
DB4 0.39 0.57 0.58 0.65
DB5 0.47 0.52 0.61 0.74
DB6 0.39 0.54 0.55 0.68
DB7 0.46 0.58 0.58 0.55
DB8 0.53 0.56 0.67 0.59
DB9 0.51 0.57 0.65 0.59
DB10 0.49 0.54 0.64 0.57
Table 1.3 Mean skid resistance values on Komghatta Road
Stretch Location
Mean Skid
Resistance
On Wet
Pavement
Mean Skid
Resistance
On Mud
Pavement
Mean Skid
Resistance
On Dry
Pavement
Mean
Texture
Depth
Komghatta Road
KR1 0.42 0.31 0.62 0.54
KR2 0.41 0.34 0.56 0.41
KR3 0.41 0.32 0.66 0.58
KR4 0.41 0.36 0.72 0.55
KR5 0.44 0.29 0.7 0.49
KR6 0.51 0.3 0.68 0.48
KR7 0.48 0.31 0.69 0.59
KR8 0.57 0.31 0.71 0.68
KR9 0.44 0.38 0.75 0.64
KR10 0.42 0.33 0.7 0.66
Table 1.4 Mean skid resistance values on GSSIT College Road
33
Stretch Location
Mean Skid
Resistance
On Wet
Pavement
Mean Skid
Resistance
On Mud
Pavement
Mean Skid
Resistance
On Dry
Pavement
Mean
Texture
Depth
GSSIT College Road
GR1 0.23 0.19 0.3 0.53
GR2 0.23 0.21 0.3 0.57
GR3 0.23 0.22 0.3 0.51
GR4 0.19 0.19 0.27 0.51
GR5 0.18 0.18 0.26 0.58
GR6 0.18 0.19 0.27 0.43
GR7 0.23 0.19 0.3 0.5
GR8 0.23 0.22 0.3 0.56
GR9 0.21 0.23 0.27 0.44
GR10 0.23 0.19 0.3 0.56
0.5 0.55 0.6 0.65 0.7 0.750.4
0.45
0.5
0.55
0.6
0.65
0.7
f(x) = − 0.285545023696683 x + 0.757322274881517R² = 0.160411073918183
SR V/S TD (Wet)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 1 shows skid resistance v/s texture depth for wet condition at Nagadevanahalli Arch
34
0.45 0.5 0.55 0.6 0.65 0.7 0.750.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
f(x) = 0.103672985781991 x + 0.36489336492891R² = 0.019720404904183
SR V/S TD (Mud)
TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 2 shows skid resistance v/s texture depth for mud on pavement condition at
Nagadevanahalli Arch
0.5 0.55 0.6 0.65 0.7 0.750.55
0.6
0.65
0.7
0.75
0.8
f(x) = − 0.143364928909953 x + 0.82303317535545R² = 0.0304202654942646
SR V/S TD (Dry)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 3 shows skid resistance v/s texture depth for dry condition at Nagadevanahalli Arch
35
0.5 0.55 0.6 0.65 0.7 0.75 0.80.3
0.35
0.4
0.45
0.5
0.55
0.6
f(x) = − 0.147856517935259 x + 0.548818897637796R² = 0.0299733125122654
SR V/S TD (Wet)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 4 shows skid resistance v/s texture depth for wet condition at Dodda Basti Road
0.5 0.55 0.6 0.65 0.7 0.75 0.80.45
0.475
0.5
0.525
0.55
0.575
0.6
f(x) = 0.0778652668416449 x + 0.524645669291339R² = 0.00697417854636695
SR V/S TD (Mud)
TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 5 shows the skid resistance v/s texture depth for mud on pavement condition at
Dodda Basti Road
36
0.5 0.55 0.6 0.65 0.7 0.75 0.80.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
f(x) = − 0.0554097404491109 x + 0.644409448818898R² = 0.00674862223418593
SR V/S TD (Dry)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 6 shows the skid resistance v/s texture depth for dry condition at Dodda Basti Road
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70.35
0.4
0.45
0.5
0.55
0.6
f(x) = 0.20464135021097 x + 0.335991561181435R² = 0.108175536623783
SR V/S TD (Wet)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 7 shows the skid resistance v/s texture depth for wet condition at Komghatta Road
37
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70.2
0.25
0.3
0.35
0.4
f(x) = 0.0708257986738999 x + 0.285195901145268R² = 0.0472171991159331
SR V/S TD (Mud)
TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 8 shows the skid resistance v/s texture depth for mud on pavement condition at
Komghatta Road
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70.5
0.55
0.6
0.65
0.7
0.75
0.8
f(x) = 0.429776974080771 x + 0.437465340566607R² = 0.459244634724001
SR V/S TD (Dry)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 9 shows the skid resistance v/s texture depth for dry condition at Komghatta Road
38
0.4 0.45 0.5 0.55 0.60.15
0.17
0.19
0.21
0.23
0.25
f(x) = 0.136382196815027 x + 0.143217639853001R² = 0.102593814721214
SR V/S TD (Wet)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 10 shows skid resistance v/s texture depth for wet condition at GSSIT College Road
0.35 0.4 0.45 0.5 0.55 0.60.1
0.15
0.2
0.25
0.3
f(x) = − 0.0730910575745203 x + 0.238934258881176R² = 0.0486368003934541
SR V/S TD (Mud)
TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 11 shows the skid resistance v/s texture depth for mud on pavement condition at
GSSIT College Road
39
0.4 0.45 0.5 0.55 0.60.25
0.27
0.29
0.31
0.33
0.35
f(x) = 0.117190690077583 x + 0.226178031849735R² = 0.128864858437801
SR V/S TD (Dry)
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 12 shows skid resistance v/s texture depth for dry condition at GSSIT College Road
0.5 0.55 0.6 0.65 0.7 0.750.40
0.43
0.45
0.48
0.50
0.53
0.55
f(x) = − 0.27361769352291 x + 0.645965244865721R² = 0.613232201322048
Dynamic Skid Resistance at 20 Kmph
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 13 shows skid resistance v/s texture depth for dry condition in Nagadevanahalli
Arch
40
0.5 0.55 0.6 0.65 0.7 0.75 0.80.35
0.40
0.45
0.50
0.55
f(x) = − 0.00917663069894037 x + 0.442498687664042R² = 0.000580425826797737
Dynamic Skid Resistance at 20 Kmph
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 14 shows skid resistance v/s texture depth for dry condition at Dodda Basti Road
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70.40
0.45
0.50
0.55
f(x) = − 0.0515973477998787 x + 0.490864376130199R² = 0.0606545970840845
Dynamic Skid Resistance at 20 Kmph
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 15 shows the skid resistance v/s texture depth for dry condition at Komghatta Road
41
0.4 0.45 0.5 0.55 0.60.35
0.37
0.39
0.41
0.43
0.45
0.47
0.49
f(x) = 0.121518987341772 x + 0.373198312236287R² = 0.070790222999069
Dynamic Skid Resistance at 20 Kmph
MEAN TEXTURE DEPTH
MEA
N S
KID
RESI
STAN
CE
Graph 16 shows skid resistance v/s texture depth for dry condition in GSSIT College Road
0.4 0.45 0.5 0.55 0.6 0.65 0.70
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
drywetmud on pavement
Texture Depth
Skid
Res
istan
ce
Graph 17 shows comparision between texture depth v/s sampled portable skid values
42
0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.80.40
0.42
0.44
0.46
0.48
0.50
0.52
f(x) = − 0.27361769352291 x + 0.645965244865721R² = 0.613232201322048
SR Portable
SR D
ynam
ic
Graph 18 shows comparision b/w skid resistance values for portable and dynamic skid
resistance tester for Nagadevanahalli Road
0.38 0.43 0.480.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
f(x) = − 0.858704974271014 x + 0.994082332761579R² = 0.41264203038085
SR Portable
SR D
ynam
ic
Graph 19 shows comparision b/w skid resistance values for portable and dynamic skid
resistance tester for Dodda Basti Road
43
0.5 0.55 0.6 0.65 0.7 0.75 0.80.42
0.43
0.44
0.45
0.46
0.47
0.48
0.49
0.50
f(x) = − 0.0623742454728361 x + 0.486169282360831R² = 0.238284785942068
SR Portable
SR D
ynam
ic
Graph 20 shows comparision b/w skid resistance values for portable and dynamic skid
resistance tester for Komghatta Road
0.24 0.26 0.28 0.3 0.320.36
0.38
0.40
0.42
0.44
0.46
0.48
0.50
f(x) = 0.94814814814815 x + 0.164148148148148R² = 0.459292254392473
SR Portable
SR D
ynam
ic
Graph 21 shows comparision b/w skid resistance values for portable and dynamic skid
resistance tester for GSSIT College Road
44
CHAPTER 5
DISCUSSIONS AND CONCLUSION
5.1 Discussion
1). The portable skid resistance values for Nagadevanahalli Road varies from 0.68 to 0.81 for dry
condition, 0.54 to 0.64 for wet and 0.32 to 0.47 for mud on pavement condition with texture
depth varying from 0.52 to 0.57 mm.
2). The portable skid resistance values for Doddabasti Road varies from 0.56 to 0.65 for dry
condition, 0.38 to 0.53 for wet and 0.42 to 0.6 for mud on pavement condition with surface
texture varying from 0.41 to 0.45 mm.
3). The portable skid resistance values for Komghatta Road varies from 0.56 to 0.75 for dry
condition, 0.42 to 0.57 for wet and 0.29 to 0.38 for mud on pavement condition with surface
texture varying from 0.44 to 0.49 mm.
4). The portable skid resistance values for GSSIT College Road varies from 0.26 to 0.3 for dry
condition, 0.18 to 0.23 for wet and 0.19 to 0.23 for mud on pavement condition with surface
texture varying from 0.41 to 0.47 mm.
5). The dynamic skid resistance values for Nagadevanahalli Road varies from 0.45 to 0.59, 0.41
to 0.49 for Dodda basti road, 0.44 to 0.49 for Komghatta Road and 0.41 to 0.46 for GSSIT
College Road for dry pavement condition.
6). The best fit curve for Dynamic Skid Resistance at 20 Kmph was obtained as y = -0.2736x +
0.646 for Nagadevanahalli Arch and y = -0.0092x + 0.4425 for Dodda basti Road, y = -0.0516x
+ 0.4909 for Komghatta Road and y = 0.1215x + 0.3732 .
45
5.2 Conclusion
1).From the test results observed at Nagadevanahalli Arch it can be concluded that the pavement
has good macrotexture as it offers good drainage even in wet pavement condition and hence the
functional condition is good.
2). From the test results observed at Dodda basti Road it is observed that the pavement has high
skid resistance as it has good microtexture and hence no mainainence work is required.
3). From the test results observed at Komghatta Road it is observed that the road stretch has good
microtexture as the road is a newly constructed stretch thereby offering high functional
performance.
4). From the tests results it is observed that the pavement is in a bad condition as the skid
resistance value is very low and the road stretch is completely raveled thereby it needs
immediate repair.
5). The skid resistance value obtained from portable skid resistance tester and dynamic friction
tester show a correlation and the variation may be due to speed and contact area.
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REFERENCES
1). DSIR, Technical symphonium on “Research on road safety”, HMSO, London.
2). National co-operative Highway Research programme 14, Report on “Skid resistance”, 1972.
3). Indian Road Congress- Highway Research Board, State of Art”-“Pavement slipperiness and
Skid Resistance “special report-2 IRC, New Delhi-1976.
4). Bobkov .V.F, “Road Condition and Traffic Safety”, Mir publishers, Mascow, 1975.
5). Corley-Lay, Jayawickrama and Thomas “Skid Resistance depends on Pavement surface
Macro and Micro texture” in 1998
6). James.C, Wambold and John Jewett Henry, Pennsylvania transportation institute studies
(USA) 1982 on “Evaluation of Pavement Surface Texture Significance and Measurement
Techniques”.
7). Giles, C.G. and Sabey, Barbara E, “Skidding as a factor in Accidents on the roads of Great
Britain”, First International Skid Prevention Conference, Part-1, August 1959.
8). Don L, Ivey, Charles J. Keese, A.H. Neill, and J.Cecil Brenner, “Interaction of Vehicle and
Road Surface”, Highway Research Record-376, Highway Research Board, Washington D.C.,
1971.
9). Goodwin, W.A. “Pre-evaluation of Pavement Materials for Skid Resistance”, A Review of
U.S.A. Techniques, HRB, Special Report101, 1969.
10). Kentucky Department of Highways, “Proposed Specification for Open Graded Friction
Courses”, Kentucky Department Of Highways, Research Report-Division Of Research 1974.
11). Wood, K.B., “Highway Engineering Handbook”, Mcgraw Hill Book Company, 1960.
12).Texas Department of Transportation and the Federal Highway Administration Report 0-
5627-3, September 2010
13).State Materials Office FDOT Research Report FL/DOT/SMO/03-464, July 2003
47
14).Virginia Tech Transportation Institute Annual Report Center for Sustainable Transportation
Infrastructure: Report No.: FHWA/VTRC 10-CR6
15). NCHRP Guide for Pavement Friction, Virginia State University, February 2009
16). Technical Memorandum: UCPRC-TM-2008-05 by California Department of Transportation
(Caltrans) Division of Research and Innovation and Division of Maintenance, April 2009
48