Report on basic skid resistance test

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

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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

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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.

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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.

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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.

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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

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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.

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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).

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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)

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`

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

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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.

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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)

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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

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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

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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

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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)

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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

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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

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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

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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

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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


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


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


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


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


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


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


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


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



4). The portable skid resistance values for GSSIT College Road varies from 0.26 to 0.3 for dry



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.

46

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

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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

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Report on basic skid resistance test

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