highway engineering/ transportation engineering-i

Elements of a Typical Cross-section of

Road and Highway drainage

Transportation Engineering – ISubrat Kumar Padhy

Pavement surface characteristics

• For safe and comfortable driving four aspects of the pavement surface are important.

• It includes :-– Friction between the wheels and the pavement

surface.– Smoothness of the road surface– The light reflection characteristics of road.– Drainage of water.

Friction between the wheels and the pavement surface.

• It is a crucial factor in the design of horizontal curves.

• It affects the acceleration and deceleration ability of vehicles

• Lack of adequate friction can cause skidding or slipping of vehicles.– Skidding happens when the path traveled along the

road surface is more than the circumferential movement of the wheels due to friction.

– Slip occurs when the wheel revolves more than the corresponding longitudinal movement along the road

• Various factors that affect friction are:– Type of the pavement (like bituminous, concrete, or

gravel),– Condition of the pavement (dry or wet, hot or cold, etc),– Condition of the tyre (new or old), and– Speed and load of the vehicle.

• The frictional totally depends upon a factor called the coefficient of friction and denoted as f.– IRC suggests the coefficient of longitudinal friction as

0.35-0.4 useful in sight distance calculation.– Coefficient of lateral friction as 0.15 useful in horizontal

curve design

Friction between the wheels and the pavement surface.

Pavement Unevenness• Even if a road is constructed with high quality pavers, it is

possible to develop unevenness due to pavement failures.• Unevenness affects the vehicle operating cost, speed, riding

comfort, safety, fuel consumption and wear and tear of tyres.• Pavement Unevenness is measured in terms of Unevenness

index.• Unevenness index is a measure of unevenness which is the

cumulative measure of vertical undulations of the pavement surface recorded per unit horizontal length of the road.

• An unevenness index value– Less than 1500 mm/km - good– Less than 2500 mm/km - satisfactory– Greater than 3200 mm/km - uncomfortable even for speed

of 55 kmph.

Pavement Unevenness

Light refection characteristics• It is necessary that the road surface should be

visible at night and reflection of light from the road surface should be less.

• White roads have good visibility at night, but caused glare during day time.

• Black roads has no glare during day, but has poor visibility at night

• Concrete roads has better visibility and less glare.• Wet pavement surface can cause high glare.

– Glare is difficulty seeing in the presence bright light such as direct or reflected sunlight or artificial light such as car headlights at night.

https://en.wikipedia.org/wiki/Light

https://en.wikipedia.org/wiki/Sunlight

https://en.wikipedia.org/wiki/Headlamp

Light refection characteristics

Drainage• The pavement surface should be absolutely

impermeable to prevent seepage of water into the pavement layers.

• Further, both the geometry and texture of pavement surface should be such that it drain out all the water from the surface in less time.

• Drains should be provided on one side or both side of the road pavement

Typical Road Cross-Section

Kerb

Cross-Section ElementsThe cross section of a road includes some or all of the following elements: – Right of way.– Carriage way– Camber or cross slope.– Kerbs– Road margins.

• Shoulders• Parking lanes• Bus-bays• Service roads.• Footpath.• Guard rails

Right of Way• Right of way (ROW) or land width is the width of land acquired

for the road, along its alignment. • It should be adequate to accommodate all the cross-sectional

elements of the highway and may reasonably provide for future development.

• The width of right of way is governed by:– Width of formation of road.– Height of embankment or depth of cutting– Side slopes of embankment or cutting– Drainage system– Sight distance considerations – Reserve land for future widening

• According to IRC normal width of ROW– For 2 lane road = 150 ft width of area (46m)– For 4 lane road = 250 ft width of area (76m)– For 8 lane road = 300 ft width of area (91m)

Right of Way

Traveled Way or Carriage Way

• The portion of the roadway provided for the movement of vehicles, exclusive of shoulders.

• Number of lanes on a traveled way are decided on the basis of expected traffic volumes and appropriate level of service required for the facility.

• Width of a lane depends on the width of the vehicle and the clearance needed.

• According to IRC – Minimum of lane width of 3.75 m - Single lane road.– Two lane road require minimum of 3.5 meter for each lane

total 7m for both lane.

Carriage Way Width

Road Way• The portion of a highway provided for

vehicular use. • It includes both carriageway and

shoulders.

Shoulders• Shoulders are the strips provided on both sides of

the carriage way.• A minimum width of 2.5 m is recommended for 2-

lane highways in India. (max 4.5m)

Functions of shoulders• accommodation of stopped vehicles

(disabled vehicles, bus stops)• emergency use• lateral support for the pavement• space for roadside facilities• space for bicycles and pedestrians• driving comfort (freedom from strain)• improvement in sight distance• improvement in capacity

Camber• Camber is the cross slope provided to raise middle of

the road surface in the transverse direction to drain off rain water from road surface.

• Too steep slope is undesirable for it will erode the surface.

• Camber is measured in 1 in n or n% (Eg. 1 in 50 or 2%)

• The objectives of providing camber are:– Surface protection especially for gravel and bituminous

roads– Sub-grade protection by proper drainage.– Quick drying of pavement which in turn increases safety.

Types of Camber

IRC Values for camber

Surface type Heavy rain Light rainConcrete/Bituminous 2 % 1.7 %

Gravel/WBM 3 % 2.5 %

Earthen 4 % 3.0 %

Kerb• It is the dividing line between carriageway

and footpath.

Types of Kerbs

• Low or mountable kerbs:– Height of 10 cm above the pavement edge.– With a slope which allows the vehicle to climb over easily

• Semi-barrier type kerbs– Height is 15 cm above the pavement edge.– parking vehicles, but at emergency only.

• Barrier type kerbs.– Height of 20 cm above the pavement edge – With a steep slope.

• Submerged kerb.– Provide lateral stability

Types of Kerbs

Functions of Kerbs

• Drainage control• Roadway edge delineation• Right-of-way reduction• Delineation of pedestrian walkways• Reduction in maintenance operation• Assistance in roadside development

Median or Traffic Separators

• It is the physical or painted separation provided on divided highways between two adjacent roadways.

• Medians can also be used to isolate slow and fast moving traffic in the same direction.

• Width of medians ranges from 1.2 to 2.4 m.

Median

Foot Path or side Walk

• Foot paths are provided in Urban roads

• These are raised strips constructed along both the edges of roads.

• Their minimum recommended width is 1.5 m.

Foot Path or side Walk

Bicycle and Parking lane

• Bicycle lane is a portion of the roadway designated by striping, signing, and/or pavement markings for preferential or exclusive use by bicycles and/or other non-motorized vehicles.

• Parking lane is an additional lane provided on Urban roads and streets for on-street parking.

Bicycle and Parking laneMinimum Width Requirements

Bicycle and Parking lane

Traffic Barriers or Guard rails• They are provided at the edge of the

shoulder usually when the road is on an embankment.

• They serve to prevent the vehicles from running o the embankment, especially when the height exceeds 3 m.

• Guard rails of stones painted in alternate black and white are usually used.

• They also give better visibility of curves at night under headlights of vehicles.

Traffic Barriers

Bus-bays

• Bus bays are provided by recessing the kerbs for bus stops.

• They are provided so that they do not obstruct the movement of vehicles in the carriage way.

• They should be at least 75 meters away from the intersection so that the traffic near the intersections is not affected by the bus-bay.

Bus-bays

HIGHWAY MATERAILS

Pavements

Highway pavement is a structure consisting Highway pavement is a structure consisting layers of processed materials above the layers of processed materials above the natural soil sub-grade, whose primary natural soil sub-grade, whose primary function is to distribute the applied vehicle function is to distribute the applied vehicle loads to the sub-grade.loads to the sub-grade.

The pavement structure should be able to The pavement structure should be able to provide a surface with adequate skid provide a surface with adequate skid resistance, favourable light reflecting resistance, favourable light reflecting characteristics, and low noise pollution.characteristics, and low noise pollution.

Two types of pavements • Flexible pavements • Rigid pavements.

Types Of Pavements

Flexible Pavements

Flexible pavements normally has many layers. Hence, the design of flexible pavement uses the concept of layered system.

Flexible pavements will transmit wheel load stresses to the lower layers by grain-to-grain transfer through the points of contact in the granular structure

Flexible Pavements

Typical layers of a flexible pavement

Typical layers of a conventional flexible pavement includes • Seal coat• Surface course• Tack coat• Binder course• Prime coat• Base course• Sub-base course• Compacted sub-grade• Natural sub-grade

Sealcoat

Sealcoat is a liquid that is applied to asphalt to protect it from oxidation and the damage caused by winter cracking, as well as UV rays and traffic.

In areas of the world that experience freezing and thawing, this special coat is applied.

Surface course

Surface course is the layer directly in contact with traffic loads and generally contains superior quality materials.

They are usually constructed with dense graded asphalt concrete(AC).

It provides characteristics such as friction, smoothness, drainage, etc. Also it will prevent the entrance of excessive quantities of surface water into the underlying layers.

Tack coat

It is a thin coating of tar or asphalt applied before a roads surface course is laid to form an adhesive bond.

It must be thin, uniformly cover the entire surface, and set very fast.

Binder course

In asphaltic concrete paving, an intermediate course between the base course and the surfacing material is present called binder course.

It consists of intermediate-size aggregate bound by bituminous material.

Prime coat

Prime coat is an application of a low viscosity asphalt to a granular base in preparation for an initial layer (or surface course layer) of asphalt.

It is generally • Provide adhesion between the base course and

succeeding asphalt course.• It penetrates into the layer below, plugs the voids, and

forms a water tight surface.

After applying the prime coat, it must cure for a minimum of 48-72 hours before asphalt is placed, with no rain in the forecast

Prime coat

Base course

The base course is the layer of material immediately beneath the surface of binder course.

It provides additional load distribution and contributes to the sub-surface drainage

It may be composed of crushed stone, crushed slag, and other untreated or stabilized materials.

Base course

Sub-Base course

The sub-base course is the layer of material beneath the base course

primary functions are to provide structural support, improve drainage, and reduce the intrusion of fines from the sub-grade.

A sub-base course is not always needed or used. For example, a pavement constructed over a high quality materials, In such situations, sub-base course may not be provided.

Sub-Base course

Sub grade soil

The supporting soil beneath pavement and its special under courses is called sub grade.

Undisturbed soil beneath the pavement is called natural sub grade.

Compacted sub grade is the soil compacted by controlled movement of heavy compactors.

Desirable properties

The desirable properties of sub grade soil as a highway material are• Stability• Incompressibility• Permanency of strength• Minimum changes in volume and stability

under adverse conditions of weather and ground water

• Good drainage• Ease of compaction

Soil Types

The wide range of soil types available as highway construction materials have made it obligatory on the part of the highway engineer to identify and classify different soils.

Broadly, the soil types can be categorized as Laterite soil, Moorum/red soil, Sandy soil, Alluvial soil, Clay including Black cotton soil.

Soil Types Gravel: These are coarse materials with particle size under

2.36 mm with little or no fines contributing to cohesion of materials.

Moorum: These are products of decomposition and weathering of the pavement rock. Visually these are similar to gravel except presence of higher content of fines.

Sand : Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt.

Silts: These are finer than sand, brighter in color as compared to clay, exhibit little cohesion and show dilatancy.

Clays: These are finer than silts. Clayey soils exhibit stickiness, high strength when dry, and show no dilatancy.• Black cotton soil and other expansive clays exhibit swelling and

shrinkage properties. Paste of clay with water when rubbed in between fingers leaves stain, which is not observed for silts.

Soil Types

Tests on sub-grade soil

The main function of the sub grade is to give adequate support to the pavement.

For this the sub grade should possess sufficient stability under adverse climatic and loading conditions. Therefore, it is very essential to evaluate the sub grade by conducting tests.

The tests used to evaluate the strength properties of soils are of 3 types.

• Shear tests• Bearing tests• Penetration tests

Direct Shear TestCONCEPTThe Direct Shear Test is used for determination of the consolidated drained (or undrained) shear strength of soils. The test is performed by deforming a specimen at a controlled rate on or near a single shear plane.

DESCRIPTION AND PROCEDUREThe soil sample is placed in a cubic shear box composed of a upper and lower box. The limit between the two parts of the box is approximately at the mid height of the sample. The sample is subjected to a controlled normal stress and the upper part of the sample is pulled laterally at a controlled strain rate or until the sample fails.The applied lateral load and the induced strain are recorded at given internals. These measurements are then used to plot the stress-strain curve of the sample during the loading for the given normal stress.

Direct Shear Test

Plate Bearing Test

CONCEPTIn plate bearing test, a compressive stress is applied to the soil or pavement layer through rigid plates relatively large size and the defections are measured for various stress values.The plate-bearing test was originally meant to find the modulus of sub grade reaction.

DESCRIPTION AND PROCEDUREThe setup consists of

• Plates of 75,60,45 and 30 cm diameter.• Proving ring arrangement.• Hydraulic jack• Reaction frame• Datum frame loaded with dial gauges.

Plate Bearing Test

DESCRIPTION AND PROCEDURE Modulus of sub grade reaction

• It can be defined as the pressure sustained per unit deformation of subgrade soil at a specified pressure level.

• It is directly calculated as the load imposed upon the plate(75 cm) to achieve a deflection of 1.25mm.

• This give a value in N/mm2/mm or N/mm3. Test Procedure.

• The test site is prepared and loose material is removed so that the 75 cm diameter plate rests horizontally in full contact with the soil sub-grade.

Plate Bearing Test Test Procedure.

• a seating load is applied and released after a few seconds and the settlement dial gauge is now set corresponding to zero load.

• A load is applied by means of jack and the load and settlement dial readings are noted.

• The load is increased until a deflection of 1.25mm is achieved.

• The average of three or four settlement dial readings is taken as the settlement of the plate corresponding to the applied load.

Calculation• A graph is plotted with the mean settlement

versus bearing pressure.

Plate Bearing Test

California Bearing Ratio Test

DESCRIPTION AND PROCEDURE

California Bearing Ratio (CBR) test was developed by the California Division of Highway as a method of classifying and evaluating soil-sub grade and base course materials for flexible pavements. It is a penetration test wherein a standard piston, having a 50 mm diameter is used to penetrate the soil at a standard rate of 1.25 mm/minute. The penetration at 2.5 mm and 5.0 mm penetrations is taken as the bearing value.The ratio to the bearing value of the soil sample and standard crushed rock is termed as the CBR.In most cases, CBR decreases as the penetration increases. The CBR is a measure of resistance of a material to penetration of standard plunger under controlled density and moisture conditions


Test Procedure The laboratory CBR apparatus consists of a mould 150 mm diameter with a base plate and a collar, a loading frame and dial gauges for measuring the penetration values and the expansion on soaking.The specimen in the mould is soaked in water for four days and the swelling and water absorption values are noted.The mould and the assembly is placed under the plunger of the loading frame.Load is applied on the sample by a standard plunger with dia of 50 mm at the rate of 1.25 mm/min.A load penetration curve is drawn. The load values on standard crushed stones are 1370 kg and 2055 kg at 2.5 mm and 5.0 mm penetrations respectively.CBR value is expressed as a percentage of the actual load causing the penetrations of 2.5 mm or 5.0 mm to the standard loads mentioned above.


CALCULATION

Aggregates

Aggregate is a collective term for the mineral materials such as sand, gravel, and crushed stone that are used in the construction of a pavement.

DESIRABLE PROPERTIES Strength Hardness Toughness Shape of aggregates Adhesion with bitumen Durability Freedom from deleterious particles

Aggregates tests

To decide the suitability of the aggregate for use in pavement construction, following tests are carried out.Crushing test Abrasion test Impact test Soundness test Shape test Specific gravity and water absorption test Bitumen adhesion test

Aggregate Crushing Test This test is used to determine the crushing strength of

aggregates The aggregate crushing value provides a relative measure of

resistance to crushing under gradually applied crushing load.

Test Procedure Dry aggregates passing through 12.5 mm sieves and retained

10 mm sieves are taken as test sample. The test sample is weighed and placed in the test cylinder of

11.5 mm diameter and 18 cm height in three layers each layer being tampered 25 times.

The specimen is subjected to a compressive load of 40 tonnes gradually applied at the rate of 4 tones per minute.

Then crushed aggregates are then sieved through 2.36 mm sieve and weight of passing material (W2) is expressed as percentage of the weight of the total sample (W1) which is the aggregate crushing value.

Aggregate Crushing Test

CALCULATIONAggregate crushing value = (W2/W1) x 100.A value less than 10 signifies an exceptionally strong aggregate while above 35 would normally be regarded as weak aggregates.

Abrasion test

DESCRIPTION AND PROCEDUREAbrasion test is carried out to test the hardness property of aggregates and to decide whether they are suitable for different pavement construction works. Los Angeles abrasion test is a preferred one for carrying out the hardness property and has been standardized in India.The principle of Los Angeles abrasion test is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as abrasive charge.

Abrasion testTest Procedure Los Angeles machine consists ofCircular drum

• internal diameter 700 mm • length 520

An abrasive charge (cast iron spherical balls)• 48 mm diameters• weight 340-445 g

Charge is placed in the cylinder along with the aggregates.The quantity of aggregates to be used depends upon the gradation and usually ranges from 5-10 kg.The cylinder is then locked and rotated at the speed of 30-33 rpm for a total of 500 -1000 revolutions.After this, the material is sieved through 1.7 mm sieve and passed fraction is expressed as percentage total weight of the sample. This value is called Los Angeles abrasion value.

Abrasion test

CALCULATION

Los Angeles abrasion value= (W2/W1) x 100

• W1= weight of test sample initially taken.• W2= weight of test sample that passed

through 2.36 mm sieveA maximum value of 40 percent is allowed for WBM base course in Indian conditions.

Abrasion test

Impact testDESCRIPTION AND PROCEDUREThe aggregate impact test is carried out to evaluate the resistance to impact of aggregates.

Test Procedure Aggregates passing 12.5 mm sieve and retained on 10 mm sieve is filled in a cylindrical steel cup of internal dia 10.2 mm and depth 5 cm which is attached to a metal base of impact testing machine. The material is filled in 3 layers where each layer is tamped for 25 number of blows. Metal hammer of weight 14 Kg is arranged to drop with a free fall of 38.0 and 15 number of blows are given. The crushed aggregate is allowed to pass through 2.36 mm IS sieve. The impact value is measured as percentage of aggregates passing sieve (W2) to the total weight of the sample (W1).

Impact test

CALCULATION

Los Angeles abrasion value= (W2/W1) x 100

• W1= weight of test sample initially taken.• W2= weight of test sample that passed

through 2.36 mm sieveFor bituminous macadam the maximum permissible value is 35 percent.For Water bound macadam base courses the maximum permissible value defined by IRC is 40 percent.

Impact test

Pavement materials: Bitumen

Bituminous materials or asphalts are extensively used for roadway construction, primarily because of their excellent binding characteristics and water proofing properties and relatively low cost.

Bitumen is the residue or by-product when the crude petroleum is refined

Different forms of bitumen

Cutback bitumen- Normal practice is to heat bitumen to reduce its viscosity. In cutback bitumen suitable solvent is used to lower the viscosity of the bitumen.

Bitumen Emulsion-Bitumen emulsion is a liquid product in which bitumen is suspended in a finely divided condition in an aqueous medium and stabilized by suitable material.

Bituminous primers- Bitumen Primer is a locally manufactured bitumen solution suitable for sealing and priming porous and non-porous surfaces.

Modified Bitumen-Certain additives or blend of additives called as bitumen modifiers can improve properties of Bitumen and bituminous mixes. Bitumen treated with these modifiers is known as modified bitumen.

Tests on bitumen

1. Penetration test2. Ductility test3. Softening point test4. Specific gravity test5. Viscosity test6. Flash and Fire point test7. Float test8. Water content test9. Loss on heating test

Penetration test

It measures the hardness or softness of bitumen by measuring the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds.

The penetrometer consists of a needle assembly with a total weight of 100g.

The bitumen is softened to a pouring consistency, stirred thoroughly and poured into container

A grade of 40/50 bitumen means the penetration value is in the range 40 to 50 at standard test conditions.

Ductility test Ductility is the property of bitumen that permits it to undergo

great deformation or elongation. Ductility is defined as the distance in cm, to which a standard

sample of the material will be elongated without breaking. The bitumen sample is heated and poured in the mould

assembly placed on a plate. Then the mould with assembly containing sample is kept in

water bath for about 90 minutes. The sides of the moulds are removed and the machine is

operated. The distance up to the point of breaking of thread is the

ductility value which is reported in cm. A minimum ductility value of 75 cm has been specified by the

BIS

Ductility test

Softening point test

DESCRIPTION AND PROCEDURESoftening point denotes the temperature at which the bitumen attains a particular degree of softening under the specific test conditions.The test is conducted by using Ring and Ball apparatus.sample of bitumen is suspended in liquid like water or glycerin at a given temperature. A steel ball is placed upon the bitumen sample and the liquid medium is heated at a rate of 5o C per minute.Temperature is noted when the softened bitumen touches the metal plate which is at a specified distance below. Generally, higher softening point indicates lower temperature susceptibility and is preferred in hot climates.

Softening point test

Viscosity test

Viscosity denotes the fluid property of bituminous material and it is a measure of resistance to flow.

Low or high viscosity - Result in lower stability values. High viscosity - Resist the compactive effort and thereby

resulting mix is heterogeneous. Orifice type viscometers are used to indirectly find the

viscosity of liquid binders like cutbacks and emulsions. The viscosity expressed in seconds is the time taken by

the 50 ml bitumen material to pass through the orifice of a cup, under standard test conditions.

Viscosity of a cutback can be measured with either 4.0 mm orifice at 25o C or 10 mm orifice at 25 or 40o C.

Viscosity test

Flash and fire point test

At high temperatures depending upon the grades of bitumen materials converts in to volatile substance.

And these volatiles catches re which is very hazardous and therefore it is essential to qualify this temperature test for each bitumen grade.

BIS defined the flash point as the temperature at which the vapor of bitumen momentarily catches fire in the form of flash under specified test conditions.

The fire point is defined as the lowest temperature under specified test conditions at which the bituminous material gets ignited and burns.

Flash and fire point test

Specific gravity test

The density of bitumen is greatly influenced by its chemical composition. Increase in mineral impurities cause an increase in specific gravity.The specific gravity of bitumen is defined as the ratio of mass of given volume of bitumen of known content to the mass of equal volume of water at 27 0C. The specific gravity can be measured using either pycnometer or preparing a cube specimen of bitumen in semi solid or solid state. The specific gravity of bitumen varies from 0.97 to 1.02.

Specific gravity test

Loss on heating test

When the bitumen is heated it loses the volatility and gets hardened.

About 50gm of the sample is weighed and heated to a temperature of 163 0C for 5hours in a specified oven designed for this test.

The sample specimen is weighed again after the heating period and loss in weight is expressed as percentage by weight of the original sample.

Bitumen used in pavement mixes should not indicate more than 1% loss in weight, but for bitumen having penetration values 150-200 up to 2% loss in weight is allowed.

Loss on heating test

Bituminous mix designRequirements of Bituminous mixes

Stability - Stability is defined as the resistance of the paving mix to deformation under traffic load. Two examples of failure are

(i) Shoving - a transverse rigid deformation which occurs at areas subject to severe acceleration

(ii) Grooving - longitudinal ridging due to channelization of traffic.

Primarily of the aggregates and the cohesion offered by the bitumen The stability decreases when the binder content is high and when the particles are kept apart.

Bituminous mix design


Durability- Durability is defined as the resistance of the mix against weathering and abrasive actions. Weathering causes hardening due to loss of volatiles in the bitumen. Abrasion is due to wheel loads which causes tensile strains. Typical examples of failure are

pot-holes- deterioration of pavements locally stripping-lost of binder from the aggregates and

aggregates are exposed. Disintegration is minimized by high binder content since they cause the mix to be air and waterproof and the bitumen film is more resistant to hardening.


Flexibility- Flexibility is a measure of the level of bending strength needed to counteract traffic load and prevent cracking of surface.

Fracture is the cracks formed on the surface (hairline-cracks, alligator cracks), main reasons are shrinkage and brittleness of the binder.

Shrinkage cracks are due to volume change in the binder due to aging.

Brittleness is due to repeated bending of the surface due to traffic loads. Higher bitumen content will givebn better flexibility and less fracture.


WorkabilityWorkability is the ease with which the mix can be laid and compacted, and formed to the required condition and shape.This depends on the gradation of aggregates, their shape and texture, bitumen content and its type. Angular, flaky, and elongated aggregates decreases workability.Rounded aggregates improve workability


Desirable properties Stability to meet traffic demand Bitumen content to ensure proper binding and water proofing Voids to accommodate compaction due to traffic Flexibility to meet traffic loads, esp. in cold season Sufficient workability for construction Economical mix

Dedicated to Sanjay….

The idea of this presentation is not to make you pass in the exam.

The only idea is to save at least some of the 1.2 millions killed in road accidents every year.

If at least one life can be saved, that will be a great success.

Road Accident Statistics

More than 1.2 million people are killed in Road Accidents, worldwide , every year.

3 to 4 % of Gross National Product Is lost in Road Accidents.

One child is killed in Road Accidents, every three minutes in the World.

Causes of road accidentsThe various causes of road accidents are:

Road Users - Excessive speed and rash driving, violation of traffic rules, failure to perceive traffic situation or sign or signal in adequate time, carelessness, fatigue, alcohol, sleep etc.


Vehicle - Defects such as failure of brakes, steering system, tyre burst, lighting system .


Road Condition - Skidding road surface, pot holes, ruts.

Causes of road accidents

The various causes of road accidents are:

Road design - Defective geometric design like inadequate sight distance, inadequate width of shoulders, improper curve design, improper traffic control devices and improper lighting,.


Environmental factors -unfavorable weather conditions like mist, snow, smoke and heavy rainfall which restrict normal visibility and makes driving unsafe.


Other causes-improper location of advertisement boards, gate of level crossing not closed when required etc..

Measures To Reduce Accident Rate.

There are three measures are generally termed "3-Es". To reduce accident rates.

• Engineering• Enforcement • Education

Engineering measures. Road design : The geometric design features of the road

such as sight distances, width of pavement, horizontal and vertical alignment design details and intersection design elements, the pavement surface characteristics including the skid resistance values - are checked and corrected if necessary.

Preventive maintenance of vehicles : The braking system, steering and lighting arrangements of vehicles plying on the roads may be checked at suitable intervals


Before and after studies : The record of accidents and their patterns for different locations are maintained by means of collision and condition diagrams. • After making the necessary improvements in design

and enforcing regulation, it is again necessary to collect and maintain the record of accidents "before and after" the introduction of preventive measures to study their efficiency.

Road lighting : Proper road lighting can decrease the rate of accidents.• Lighting is particularly desirable at intersections, bridge

sites and at places where there are restrictions to traffic movements.


Enforcement Measures Speed control : To enable drivers of buses to develop

correct speed habits tachometers may be fitted so as to give the record of speeds. • Also surprise checks on the spot should be done at

selected locations Traffic control devices Signals may be re-designed or

signal system fee introduced if necessary, Similarly proper traffic control device like signs, markings or channelizing islands may be installed wherever found necessary.

Training and supervision : The transport authorities should be strict in testing and issuing license to drivers of public service vehicles and taxis.• Driving license of the driver may be renewed after

specified period, only after conducting some tests to check whether the driver is fit.


Enforcement Measures Medical check : The drivers should be tested for

vision and reaction time at prescribed intervals, say, once in three years.

Special precautions for commercial vehicles : It may be insisted on having a conductor or attendant to help and give proper direction to drivers of heavy commercial vehicles.

Observance of lam and regulation : Traffic or transport authorities should send groups of trained personnel, assisted by police to different locations to effect whether the traffic regulations are being followed by the road users and also to enforce the essential regulations.


Educational Measures Education of road users : It is very essential to educate

the road users for various precautionary measures to use the road way facilities with safety. • The passenger and pedestrians should be taught

the rules of the road.• The Indian Roads Congress has recently prepared

Highway Safety Code and the document on Road Safety for school children.

Safety drive:- Imposing traffic safety week where the road users are properly directed by the help of traffic police and transport staff. • Roads users should be impressed on what should

and what should not be done, with the help of films and documentaries.

• The IRC has been organizing Highway Safe Workshop in different regions fee country.