INTRODUCTION
Index plan → Roads and bridge project
Zero mile stone → Nagpur
Wind resistance on vehicle =CAV2
Development of Highway → (RaTTe M)
Roman→ Trezeguet → Metcalf → Telford →Macadam constⁿ
CPWD → Est. by Lord Dalhousie in 1865
Longest road (GT rd Lahore-WB) → Constructed during the time of Shershah suri in 1545
Road foundation for modern highway → Macadam
imp years (JRC IMC)
1927 → Jaykar committee
1928: Recommendation by Jaykar committee
1929: CRF,Central road fund
1930: CRO, Central road organisation
1934 → IRC (Indian Road Congress)
1939 → Motor vehicle act
1952: CRRI central road research institute
1956: National Highway Act
1960: BRO
1978 : National transport policy
Road Length
NH = Area(Km²)/50
SH = 2 x NH = Area/25 or (62.5 x no of town - NH)
MDR = 4 x NH = Area/12.5 or (90 x no of Town)
Total Road length = 4.74 x (Town + village) or 82 km/100km²
VR = Total Road length - NH - SH - MDR
Urban road → Road within a city or town
Road patterns
Radial/Star & circular → New delhi connaught place
Radial/Star & rectangular =
Rectangular or block pattern = Chandigarh
Radial/Star & Grid = Nagpur road plan
Hexagonal pattern
Factor controlling alignment
Obligatory site → Bridge site, zoo, town, temple
Traffic requirement → O & D study (desire line), Show trend of traffic
Geometric requirement → Site distance requirement
Economy → Cost/benefit ratio
Hydrological factor, drainage factors
Engineering survey for highway
Map locatⁿ(Topographic) → Reconnaissance →Preliminary → Detail locatⁿ → construction Survey
Map study (Topographic) → Possible alternative routes, Alignment avoiding hill, lake
Reconnaissance → General characteristics , No of cross drainage str, soil type, HFL, source of construction material, appx gradient
Preliminary survey → Physical info, To survey various alignment, soil survey, material survey, traffic study, appx cost
Final location → Based on preliminary survey
Detailed survey → Levelling along final centre line, Temporary BM est → at 250m, at all drainage and underpass str,
Realignment of highway → to improve horizontal and vertical alignment
Economic survey → Detail study of Agricultural and industrial products available in the area
Rolling starts from sides & processed to centre in Highway construction.
Preparation of Highway → long + cross sectⁿ require
Cross-sectⁿ for a highway is taken, i). Right angle to the centre line, ii). 30m apart, iii). intermediate points having abrupt change in gradient
Max utility system → Concept of max utility per unit length of road
Alignment of highways → Layout of its centre line on ground
Imp NH
1 → Delhi-Ajmer
1A → Jalandhar-uri
3 → Agra-mumbai
7 → Varanasi - kanyakumari
9 → Pune-solapur-hyderabad-vijayawada
PMGSY (2000)
Rural road development
GEOMETRIC DESIGN
Proper geometric designs will help in Reductions in accident
Delineators → light reflecting device
min. width of cycle Track = 2m
Geometric design
Object → Efficiency of traffic operation, Safety increase at reasonable cost
Deals With → Vehicle dimension design, Road user characteristics, Topography, Highway classification (traffic vol), design speed, horizontal & vertical curve, Gradient, Sight distance
Formation/Roadway width = Carriageway width (includes median) + shoulder
Roadway = carriage way + 2 x Shoulder width + separator
Right of way or Rd Land width = Carriageway + shoulder + road margins = formation width + Road margin (Guard rails, footpath, cycle track, service road etc)
ROW → Width is Governed by → Width of formation, Height & side slope of embankment or cutting, Drainage, sight distance, horizontal curves & Reserve land for future widening
Carriage way → Used by vehicular traffic
Building line → A line on either side of the road between which And The Road, No building activity is permitted at all
Submerged kerbs → Provided on rural roads between pavement edge and shoulders, To provide lateral confinement to the base course in flexible pavement
PIEV
Perception → Nervous system
Intellection → Old memories, New thought
Emotion → Fear, angry
Volition → Acts
t = 2.5 sec → For SSD (90th percentile reactⁿ time), Break reaction time
t = 2sec → For OSD
Factor affecting Reaction time of Driver
Mental condition of driver
Nature/Type of object
Size of object → t ∝ 1/Size of object
Vehicle speed → t ∝ 1/V
Size/length of vehicle → t ∝ Size of vehicle
Distance of object → t ∝ D
Note → acc IRC Total reacⁿ time doesn't depends on speed of Vehicle
Design Speed
Urban roads → Arterial = 80 kmph, Sub-arterial = 60, Collector road = 50, Local = 30
C/S Elements
Unevenness/Smoothness → Bump-indicator → in terms of Unevenness index , & also for long frictⁿ
Roughness index → Cumulative deformation of surface per horizontal distance
Drainage → Transverse drains are used when soil is relatively less Permeable
Catch water Drain → Provided parallel to the roadway to intercept & divert the water from hill slopes.
Light Reflection → Concrete rd have better visibility & less glare
White road → Good visibility in night, Cause glaring in day
Black road →No glaring in day but poor visibility in night
Friction
Slipping → θ > L, Skidding → L > θ
lateral f = 0.15 → Used for e
long. f = 0.35 → Used for SSD
Retardation = fg = 9.81f
Frictional resistance → Can't overcome by the engine of vehicle moving at certain speed
Chamber/Cross fall
Rising in the middle of the road surface....
Slope provided in transverse direction → for effective Drainage of water
Recommended shape → Straight at edges and parabolic in middle (Mixed camber)
Shoulder chamber = Pavement camber + 0.5% steeper, should be ≥ 3%
On superelevation section → Shoulder camber = Pavement camber
Min gradient on roads → 0.5 %
Longitudinal gradient = 2 x Chamber → G = 2C → Conditⁿ of smooth flow & necessary drainage
Composite Camber → Straight edge & Parabolic or circular Crown, for mixed traffic conditⁿ
Two Straight line C → Straight edge & Flatter Crown.
Provision of Camber is Affected by Amount of rainfall
Scanty rainfall regions → Flatter camber is provided
Round shape is not Preferable in Chamber
Excess camber → Erosion of berms, unequal wear of tyre, discomfort
Tendency of most vehicle to run along Centre lines → Problem of toppling of bullock cart and truck (heavily loaded)
Street inlet for drainage of water are located → An interval of 30 - 60 m
min furrow grade to assure surface drainage → 0.05%
Ht. of Crown = ½Pavement width x Camber
Straight line chamber
y = w/2n → 1/n = 2y/w
Cement concrete , w = width of Rd, y = crown ht, n = camber (1 in n)
Barrel or Parabolic chamber
A continuous curve either parabolic or elliptical
y = 2x²/nw
Bitumen & fast moving vehicle
Angle of inclination of the vehicles → More at edges
Range of Chamber or Minimum superelevation
Chamber → Earthen > Gravel > WBM > CC > High Bituminous
Hill rd → Heavy rainfall
Cross-Slope
Plain = 0 - 10%
Rolling = 10 - 25 %
Mountain = 25 - 60%
Steep > 60%
Cross slope ↑ → Radius of curvature ↑ → Construction cost ↑
Design ↓ → R ↓ → Construction cost ↓
IRC Recommendations
IRC → All Specifications for Highway Planning & Design
Std loading → Class A → in general for all permanent structure
Roads in rural areas → Design for 10 - 15 years
Ruling slope < 1 in 20
Maximum load of axle of a vehicle < 8170 kg
Vehicle Dimensions
Width ≤ 2.44m for all vehicles
Height → Single deck ≤ 3.80m, Double deck ≤ 4.75m → Define vertical clearance
Length ≤ 18m
Width of Vehicle → Determine pavement width, Shoulders, Parking, Traffic lanes width
Length of Vehicle → Extra widening, Min radius of turning, Passing sight distance, Goverens turning path
Carriage way width (m)
For all type of road's
Pavement width → Depends only on number of lanes
Single lane = 3.75 m
Two lane, no kerbs = 7.0 m
Two lane raised kerbs = 7.5 m
intermediate carriage = 5.5 m → To give manoeuvring
Kerbed urban road = 5.5 m
Multi-Lane = 3.5m per lane
Width of Roads
Single lane NH or SH = 12m (plain & rolling) & 6.25m(Hill or steep)
min width of NH = 5.7m
Width of formation = 6.7 m
Absolute min width of median/Traffic separator
IRC → Desirable = 5m, Min = 3m
Urban = Absolute = 1.2m
Shoulder
Rougher than the traffic lines
Min width = 2.5 m
2 lane rural highway ≥ 2.5m
Desirable = 4.6m
Footpath
Ht = 15 - 20cm
Width = 1.5m
Stopping Sight distance/SSD/Absolute min Sight dist./Non passing Sight dist
Distance of sufficient length to stop the vehicle without collision
SSD = lag distance + Braking dist= vt + v²/2g(f ± S%)
SSD = 0.278Vt + (Vi² - Vf²)/254(ηf ± S%)
Lag distance → Travelled during PIEV time or Reaction time
f = 0.35, t = 2.5sec, η = braking efficiency, +S% = upgrade, -S% = downgrade
f = longitudinal coeff of frictⁿ → Measured by Bump integrator or Roughometer
Min SSD → i) 1W1L, 2W2L, HSD → SD = SSD, ii) 2W1L, ISD → SD = 2 SSD
Two vehicle approaching each other → SSD = SSD1 + SSD2
S² = 8MR → where M = Setback distance, S = SSD, R = radii
for SSD → Driver eye H = 1.2m, obstruction h = 0.15m
for OSD → H = h = 1.2m
OSD > ISD > SSD
Recommended SSD → 30 kmph design speed = 30 m
Braking efficiency (η)
η = f'/f=(V2/254L)/f
Skid resistance (f') = V2/254L=v2/2gL
L → Length of skid mark or braking distance, f → Avg skid resistance
Skid resistance = V²/127RL → L = Skid marks in m
Overtaking Sight Distance/OSD/Passing Sight Distance
Overtaking zone
min L = 3 x OSD, Desirable = 5 x OSD
t = 2sec(IRC)
min OSD = d1 + d2 + d3
d1 = 0.278Vb²t
d2 =VbT + 2S
d3 = 0.278Va²T
T = √(4S/a) .sec
S = 0.7Vb + 6 (meters)
if not given → Vb = V - 16 Km/hr, V = design speed
When no vehicle from opp side (1W traffic) → OSD = d1 + d2
For multi road lane overtaking is permitted from both left & right side
at highway stretches where the required OSD can't be provided → Provide OSD > 2SSD
HORIZONTAL ALIGNMENT
On H curve if pavement is kept horizontal across alignment then the pressure on outer wheels > inner wheels
Curve Resistance = T - Tcos
Centrifugal ratio/impact/stability factor
Cr = P/W =b/2h= v²/gR = (e + f )/(1-ef)
V = kmph, v = m/s, R = m
Max CR → Highways = 0.25 = 1/4, Railways = 0.125 = 1/8
Centrifugal force
P = mv²/R
To prevent Transverse or Lateral Skidding → f ≥ v²/gR = P/W
To prevent Overturning about outer wheel → b/2h ≥ v²/gR
For No Sliding & No Overturning → f ≥ P/W ≥ b/2h → h = C.G. of body from surface
SUPERELEVATION/Cant/Banking
Transverse inclination to the pavement service → Provide on a curve at outer edge → Rising of outer edge wrt. inner edge on horizontal curve
tanθ = e = v²/gR=Rise/Road width
Angle of banking → =tan-1 (e)
e + f = V²/127R
e min ≥ Chamber → e ≥ C
f = 0.15 → lateral frictⁿ coeff
if No superelevation → Pressure outer > inner
In highway construction on Superelevated curves the rolling shall proceed from Lower edges towards the upper edges
Equilibrium → When f = 0 , e = e equilibrium & reaction on tyre R1 = R2
Along the circular curve → e = constant
R = 1720/D
Equilibrium superelevation = e Road width
fast moving: f min & e max
Slow moving: f max & e min
Angle of banking: Slope on road surface
IRC Values
Hilly terrain not bound by snow → e < 0.10 (10% or 1 in 10)
Plain & rolling Terrain, hilly terrain bound by snow → e < 0.07 (7% or 1 in 15)
Urban roads → e < 0.04 (4% or 1 in 25)
Min super-elevation for drainage purpose → e = 2 - 4%
Max to avoid overturning of bullock carts( slow moving vehicle) → e < 1 in 15
Rotating the pavement
About the inner edge → leads to no drainage problems as well as the centre of the pavement is raised resulting in altered vertical alignment
About centre line → Vertical profile remains & advantage in balancing the earth work
Ruling Radius of Horizontal Curve
min possible radius of the circular curve on which a vehicle moving at design speed can pass the curve safely
Min R = Ruling R = V²/127(e+f)
For mixed traffic condⁿ/Design/maximum/Required
e + f = V²/225R → V ↓es by 25%
Camber = V²/225R → No superelevation require
Extra Widening
Provided at beginning of Curve
We = Mechanical + Psychological widening = nL²/2R + v/2.64√R
We = nL²/2R + V/9.5√R
R < 50m → inner side widening
R = 50 - 300m → Both edge widening
R > 300m → No extra widening
No extra widening → R > 150m for hill roads (IRC)
Full amount of We (m + p) → Beginning of the circular curve
We in hairpin bend for two lane carriageways = 1.5 m
Off-Tracking
Ot = nL²/2R
Rear wheels don't follow the same path as that of front wheels this phenomenon is called off Tracking.
Horizontal Transition Curve (Easement curve)
Alignment from straight to Circular Curve → Gradual change of Super elevation
Purpose → To provide gradually counteract centrifugal force & avoid sudden uncomfortable Condⁿ, Avoid Overturning, provide comfort, avoid sudden jerk by introducing centrifugal force, gradual introduction of superelevation & extra widening, aesthetic appearance to road.
Radii → ∞ at straight end & desired R at point of tangency
at straight edge curvature = 1/R = 1/ ∞ = 0
Full amount of super elevation is provided → At the end of Transition curve
Max rate of change of radial acceleration = 300 mm/sec³
IRC → ideal Transition curve → Spiral or Clothoid (L ∝ 1/R)
Hills → Spiral, Railway → Cubic parabola
Bernoulli's Lemniscate
Special type of transition curve → Rate of increase of curvature increases towards the circular curve
Used when deflection is very large
Objectionable in Railway but allowed on highway
Transition curve formula
Shift = L²/24R → Perpendicular offset from a tangent to the junction of a transition curve and circular curve
Offset = x³/6RL
Equation of Clothoid or Cubic Spiral Curve → y = x³/6RL
1st tangent length of combined curve → (R+S)tan(/2)+L/2
Angle of deflection = Spiral angle/3
Lemniscates curve eqn → r=P/3sin2
Length of Transition curve
i.Passenger comfort ( acc to e)
Plain & Rolling terrain → Ls = 2.7V²/R
Steep & hilly terrain → Ls = V²/R
ii. Rate of change of Centrifugal acceleration (driver's comfort criteria)
Ls = v³/CR → v in m/s
Ls = 0.0215V³/CR → V in kmph
C = 80/(75+V)≈ 0.5 - 0.8 m/sec³
iii.Method of introduction of super elevation (e)
Rotation About inner edges L = N.e.(W+We)
Rotation About centre → L = ½. N.e.(W+We)
e → Super elevation , W → Road width (1 m), N = rate of change of superelevation if 1/100 → N = 100, We → Widening
Grade compensation
Reduction in gradient at horizontal curve, which is intended to offset the extra tractive effort at curve
GC = min of (30 + R)/R % or (75/R) %
Compensated Grade → CG = (G - GC) 4%
No compensation → if G is flatter than 4% (or < 4%)
VERTICAL ALIGNMENT
VA when gradient ≥ 4mm/1m
VA are provided at change of Gradient → To join different grades
Rate of change of Gradient = d²y/dx²
Parabolic Curve → y = ax² + b
Vertical curve designated → By radius of curve, minimum sight distance, change of gradient
Desirable slope for highway embankment → 1 in 3
Minimum skid resistance number (SN) = 50 → for indian roads to have a level 1 serviceability indicator
Gradient
Rate of rise or fall of road surface along its length/alignment wrt Horizontal
Exceptional > limiting > Ruling > minimum
Floating gradient → Vehicle doesn't require Tractive effort to maintain Specific Speed
Ruling/Design G → Use in Design of vertical profile of road, Engine can haul max load
Exceptional G → Unavoidable situation, limited to 100m stretch in a single run
Limiting G → Provided when Ruling G is Very costly due to cutting & filling
Min Gradient considered with drainage point of view:(IRC)
Cement road = 1 in 500
Earthen road = 1 in 200 → Open soil drains
Bitumen road = 1 in 250
Length of vertical curve
L=(g1-g2)l/r=Total grade x chain length /Grade change per chain length
Transition length = ( g1-g2)S2/800h → s = sight distance, h = Apex height
Summit Curve
ideal summit curve is Circular → But generally Parabolic curve are used as Summit curve
Design governed by Stopping Sight distance
2W2L → Length depends upon SSD
Parabolic summit curve → Min radius = L/N
SSD given
h1 = 1.2 m, h2 = 0.15 m
L ≥ SSD → L = NS²/4.4=NS2/2(h1+h2)2
L < SSD → L = 2S - 4.4/N=2S-2(h1+h2 )2/N
N = |n1 - n2| → ex = 5 - 4% = 1% = 1/100
OSD/ISD given
h1 = 1.2 m = h2
L ≥ OSD/ISD → L = NS²/9.6
L < OSD/ISD → L = 2S - 9.6/N
Valley/Sag Curve
Design governed by Comfort Criteria & Safety criteria (Head light criteria)
Generally parabolic (froude's) curve is preferred
Changes alignment of road from downhill (descending gradient) to uphill (ascending gradient)
Minimum stoppage distance Assuming → Headlight = 0.75 m and beam tilted at an upward direction = 1 degree
Length of valley curve
L → max of comfort & safety criteria
For night travel, For min length → Head-light distance = SSD
Comfort criteria
Impact free movement → no jerk
L = 2 NV³/C = 2Ls
Safety Criteria
Taxiway
max long. grade = 3%
Permissible rate of change of grade = 1%
Transverse grade = 1.5%
TRAFFIC ENGINEERING
Traffic Census → Traffic survey for collecting traffic data
Rumble strip/Sleeper lines/Alert strips → Reduce the speed on the roads
Urban areas when cycle traffic is high → Cycle track = 2.0 m
Minimum value of 15 minute peak hour factor on section of road = 0.25
Maximum value of 15 minute peak hour factor = 1.0
Speed and Volume studies → Set of traffic studies needed for functional design as well as for highway capacity design
Design Reference flow (DRF) → Hourly flow rate
Traffic vol Study
Manual → By watch
Photography, videography → By video
Automatic countries-cum-classifiers → Not classify and record vehicle type
Mechanical methods for Traffic vol count
Pneumatic tube → Automatic, no of axles, No. of vehicle , traffic volume
Loop Detector
Magnetic detector
Multiple pen recorder → Combination of manual and mechanical
Presentation of Traffic Vol Data
Average Daily Traffic (ADT) → No of vehicle/day → Day = 7 to 365
Annual average daily traffic (AADT) → (No of vehicle /365) at a specific point → Avg daily traffic recorded for 365 days
30th highest hourly Vol → Used for road design, ADT exceed 29 times a year
30th highest hourly Vol = 8 - 10 % of AADT
Daily expansion factor = Avg total vol for a week / avg vol for a particular day
Avg Daily Traffic = Traffic Vol count x DF x SF where
DF = Daily Factor & SF = Seasonal Factor
Avg future flow = ADT(1 + r/100)n
Spot speed
instantaneous speed at a specific location
measured → Pressure contact tubes, Enoscope, Loof deflector & Doppler radar
Time mean speed (Vt)
Avg speed = Vt = ΣVi / n → Arithmetic mean
Avg of all vehicles passing a point over a duration of time → Average of spot speed
Space mean Speed (Vs)
Vs = n/ Σ(1/Vi) → Harmonic mean
Avg speed of vehicles on a certain road length at any time
Use → Traffic flow study
Vt > Vs → Arithmetic > Harmonic mean
Spot speed data Presentation
15th percentile speed → Lower safe speed
85th percentile speed → Highest Safe speed
98th percentile speed → Geometric Design speed
Model Speed → At which max vehicle running = 47 km/hr generally
Speed & Delay Studies Methods
Floating car/Riding check method → For 2 lane traffic, 4 observer require
Elevated observation
interview techniques
Licence plate method
Photographic techniques
Origin & Destination Studies
Use planning new highway & improving new existing services, locating major routes in city
Use in planning MRTS (Mass Rapid Transit System)
Desire line → Direct line connecting Origin & Destination point
Method O & D
Roadside interview method
Home interview method
Return postcard method
Tag on Car method
Licence plate method
Work spot interview method
Traffic Capacity study
Traffic Density (k) → Vehicle/km
Traffic Vol (q) → Vehicle/day or Vehicle/day
Traffic vol = traffic densitytraffic speed q=kV
Basic C → Theoretical capacity for ideal roadways & traffic conditions
Possible C → Under prevailing condⁿ
Practical or Design C → Zero to basic C, without creating unreasonable delay
Capacity of four-lane divided rural highway = 30,000 PCU
Level of services → 6 from A to F
Required number of lanes → Depends on Predicted traffic volume and design volume
Max Theoretical Capacity (C)/Traffic vol
Max Vol in the most ideal conditⁿ
C = 1000V/S = 3600/Ht
S = avg c/c spacing of vehicle or distance/space headway
S = 0.2V + L → L = 6m, V = Kph
S = Sg + L → Sg = 0.278Vt
Space headway ∝ V, t
V= kmph, Ht = sec, S = meter(min space headway)
Relatⁿ b/w V,k,q (by Green-Shield)
U = A - Bk → Usf = A, kj = A/B
Density at max flow → V = dq/dk = 0 & k = kj/2
Speed at max flow → K = dq/dv = 0 & Vs = Vf/2
Traffic Vol. → qmax = Vf Kj / 4
Kj = 1000/S → S = Space headway
max flow = Capacity Flow
Vehicle not moving → K = max & q = 0
PSU (Passenger car unit) Equivalency factor
Motorcycle, Scooter, Pedal cycle = 0.5
Three-wheeler = 0.75
Passenger car, Tempo, Auto-rickshaw = 1
Cycle rickshaw = 1.5
Bus, Truck, Tractor trailer = 3
Horse drawn vehicle = 4
Small bullock cart = 6
Large bullock cart = 8
Capacity of Road in rural areas
Daily traffic load per lane
Village road → up to 200 tonne/day
WBM → 500 tonne/day
Bitumen macadam -> 1500
Concrete → 2000
PARKING STUDY
Parking survey → Video tap
Peripheral parking → Kiss and ride
Traffic census is carried out to study → Road parking
Parking lane → Urban roads
Angle Parking
Least → 30° → N = (L - 0.85)/5.1
Best → 45° → N = (L-2)/3.6
60° → N = (L-2)/2.9
Max vehicle → 90° → N = L/2.5
Parallel parking
Min Width = 3m
Equal spacing → N = L/6.6
2 car placed close → N = L/6.75
ACCIDENT STUDY
Collision diagram → Appx path of vehicle & pedestrian involved in accident, determine remedial measure
Condition diagrams → Shows all important physical conditions of an accident location like roadway limits, bridges, trees and all detail of roadway condition
3E → Engineering, Enforcement, Education → To decrease accident rate
TRAFFIC CONTROL & REGULATIONS
Passive control → Less traffic vol, Road user has to follow rules, sign, marking, giveaway
Active control → Forced to follow path suggested by traffic agency, Signal, Grade separated intersection
Sem-control → Rotary, channelisation, driver gently guided to avoid conflict
Traffic island → Divisional island, Channelising island, Pedestrian loading, Rotary
Recommended entry angle for roundabout junction → 10 -60
Circular central island → Two equally imp roads cross roughly at right angles
Priority intersection → Traffic control on minor road by STOP or GIVEWAY signs and marking
Traffic Growth
Generated Traffic growth → ↑es in traffic due to ↑es in transport Vehicles
Normal Traffic growth → Traffic on new roads, general increase in number of transport vehicles from year to year
Road Intersection or at Grade junction
It is an area where two or more roads converge, diverge, meet or join or cross.
Conflict points are reduced to bare minimum & delays are minimised
No. of Potential Conflict
Both 1W = 6 → 4 major + 2 minor
One 2W, Other 1W = 11 → 7 major + 4 minor
Both 2W = 24 → 16 major + 8 minor
Minor conflicts→ Merging and diverging
Total conflicts = Vehicular/potential conflicts + Pedestal conflicts
Pedestal → Both 2W = 8
Types of intersection
At Grade intersection(Traffic islands,Rotary) → Road meets about same level, allow traffic manoeuvre like - Diverging, merging, crossing, weaving
Grade Separated intersections(interchange) → Permits cross flow of traffic at level without interruption Ex. crossing two highways, Overpass, Underpass
Basic requirements of the intersection at grade
Good lightning at night is desirable
Sudden change of path should be avoided
Geometric features should be adequately provided
Rotaries are self-governing and do not need practically any control by police or traffic signals
Ramp
Direct interchange ramp → Diverging to right and merging from the right
Semi-direct interchange ramp → Diverging to left and merging from the right
Indirect ramp → Diverging to left and merging from the left
Guidelines for Rotatries Selection
Rotary is useful when no of roads intersect at the interchange & sufficient Land is available
Upper limit = 3000 vehicle/hr
Lower limit = 500 vehicle/hr
Suitable when no of approaching roads > 4
Right turning traffic > 30 %
Operation → Diverging, merging, weaving(merging + diverging)
Design Element of Rotaries
Design speed at rotaries → Urban areas = 30 kmph, Rural = 40 kmph
Rentry <Rcentral island <Rexit R=V2/125f → No superelevation
Width of weaving = 1/2 of (entry + exit width) + 3.5
Min weaving length → Rural = 45m, Urban = 30m
Width of carriageway at entry and exit > 5 m
idealise entry angle = 60, Exit angle = 30
Weaving ratio(P) = Crossing traffic / Total traffic
Q (PCU/hr)=280W(1+e/W)(1-P/3) / (1+W/L)
E → entry width, W → width of weaving section, L → length of weaving section,
Road Sign
FOG → Yellow light
1. Mandatory/Prohibitory/Regulatory
Laws ,legal offence → Circular, White background & Red border, except Stop & Give way sign
Diameter = 60 cm, ht = 2.8m
Exception → Stop → Octogonal & Give Way → inverted Triangular
ex. Speed limit, Dead slow, No parking, End of speed limit, One way
Speed limit sign on NH and SH should be placed 120 m ahead from the distance where actually speed limit start
2. informatry/Guide
For info & guidance
Rectangular , Green background &
ex. directⁿ sign
3. Warning/Cautionary
Hazardous condtⁿ
Upward triangular or Diamond shape → Red borders & white background
L = 45cm
KM Milestone
NH → Yellow & white
SH → Green & white
City/MDR →Blue/Black & white
Village Rd → Orange & white
Traffic Signal
Well designated signalised intersection is one which the Total delay is minimised
Flexible progressive system → Most efficient, Best, Most suitable for mixed traffic conditions, it is possible to vary the length of cycle, cycle division, and time schedule at each signal point
Simultaneous system → Does not give continuous movement
Simple progressive system
Alternate system
Signal design methods
Minimum green time required = 16 sec
1. Trial Cycle method
Green period =2.5n1C1/900
2. Approximate method
3. Webster's method
Most rotational method
Optimum cycle time (Sec) → Co = (1.5L + 5)/(1 - Y)
Total lost time → L = 2n + R → R = all red time, n = no of phase, Y = sum of ratio of Normal & Saturation flow
Y = Σyi = Σ (qi/Si) → qi = normal flow, Si = saturation flow
Eff green time Gi = yi(Co-1)/y
Saturation flow → S = 525 W (PCU/hr), W = carriageway width(m)
4. IRC method
irc is a appx method where optimum cycle time is checked by Webster's method
Pedestrian Green time required for major & minor roads are calculated based on walking speed of 1.2 m/s.
Road lights
Avg illumination → Imp roads = 30 lux, secondary road = 4-8 lux
Spacing of light poles = Utility coeff x FOS x lamp lumen / Avg lux x Road width
Minimum vertical clearance for electric power line up to 650 volts = 6 m
Road marking
Road or traffic markings are made of lines, patterns, words, symbols or reflectors
Broken longitudinal lines → May cross
Solid longitudinal lines → Not to cross Except entry, exit, side road or to avoid stationary object
Double solid line → indicates max restrictions, only in emergency we can cross
Material → binder, glass beads, titanium dioxide
Classification of marking
i. Carriageway markings
Longitudinal marking such as centre line, traffic lanes, pedestrian crossing, border or edge lines. Bus lanes etc
No-overtaking zones, No-parking zones, warning lines .etc
ii. Marking at intersections
Stop lines, direction arrows, give way, marking on approaches to intersections, speed change lanes.
iii. Marking at hazardous location
Obstruction approaches, carriageway width transition, road-rail level crossings, check barriers.
iv. Marking for parking
Parking space limits, parking restrictions, bus stops
v. Word messages
Stop, slow, bus, keep clear, right turn only, exit only
vi. Object markings
Kerb marking, edges islands, objects within the carriageway, objects adjacent to the carriageway
HIGHWAY MATERIAL
Pavement Materials → Soil, Aggregate, Bitumen
SOIL
Granular soil → Most suitable material for Highway embankment
Subgrade soil → Stability, good drainage, ese of compaction
California Bearing Ratio (CBR)
Go to flexible pavement for more details
Plate Bearing Test
Support capability(K) of Soil or supporting power of subgrade
Both flexible & rigid footing
Plate dia = 75cm → Standard size of plate
K = P/0.125 kg/cm³ → Modulus of subgrade reactⁿ
K1 a1 = K2 a2 → a1 = 75cm
AGGREGATE
IS 2386
Part i: Shape factor, particle size, flakiness & elongation index.
Part ii: Deleterious material & organic impurities
Part iii: G, porosity, water absorption
Part iv: Crushing strength & Toughness
Part vi: Hardness & Durability
i. Crushing Test
Strength, Resistance against gradually applied load
Coarse aggregate → Passing 12.5 mm and retained on 10mm IS sieve
Crushed agg → Pass 2.36mm Sieve
Crushing value = 30 - 45 %
ii. Abrasion test
Hardness of aggregate
Road work → Coeff of Hardness > 17
Methods → Deval abrasion test, Dorry abrasion test, Los Angeles abrasion test
Attrition → Mutual rubbing & Grinding under traffic load
Abrasion → Rubbing b/w aggregate & traffic
Coeff of H = 20 - ∆W(gm)/3
Los Angeles abrasion test
6 - 12 cast iron balls of dia = 48mm & wt = 340-445gm
Sieve use = 1.7mm
Speed of drum increases → Abrasion value increases
iii.Impact Test
Toughness → Resistance against Sudden load
Champy test is a impact test
Due to dynamic load
15 blows, hammer = 13.5 - 14 kg & ht. = 38cm
Sieve = 2.36mm
iv. Soundness or Durability Test
Resistance against Weathering (durability)
Use of sodium sulphate & magnesium sulphate
Soundness index → Na2SO4 ≤ 12 %, mgSO4 ≤ 18%
v. Shape Test
Flakiness → Least dim < 0.6(3/5) x mean dim
Elongation → Length > 1.8(9/8) x mean dimension
F.I. = Flaky particle/Total Sample ≤ 15%
E.I. = Elongated particle/Total Sample ≤ 15%
vi. Angularity No
Degree of packing → % of void after proper compaction
A no. = 0 - 11
Higher no means more angular agg & less workability
vii. Specific Gravity
G = 2.6 - 2.9
viii. Water absorption
WA ≤ 0.6%
Oven drying temperature = 100 - 110 °C, For 24 ± 0.5 hours
ix. Bitumen adhesion Test
Gives a stripping value of agg @ 40°C
Stripping value of agg
Road aggregates ≤ 5%
Bituminous road constⁿ ≤ 25%
Max value suggested by IRC = 10% → For agg used in open graded premix carpet
BITUMEN
Grade of Bitumen → By Viscosity & Penetration Test
Cracked Bitumen → Spot test and Solubility test
BIS bitumen grade → A/B where : A = softening & B = penetration point
Bitumen carpet thickness = 50 - 75 mm
Minimum elastic recovery for crumb rubber modified bitumen = 50%
Should be homogeneous and shall not foam when → Heated to 175℃
Test for Bitumen
Max water content < 0.2 % by weight
i. Viscosity
Viscometer test → Consistency and flow resistance
VG 10 → Suitable for 7 day max avg air temp of 15°C, VG stand for viscosity grading
Use of VG10 - spraying application's, mfd of bitumen emulsion
VG 30 → min penetration = 45 @ 25 ℃
Order of viscosity → Seal coat > Tack coat > Prime coat
ii. Pycnometer
Specific Gravity (G)
Bitumen= 0.97 - 1.0
Tar = 1.1 - 1.25
Mix bitumen = 1.09
iii.Penetration Test:
Grade of Bitumen → Hardness or Softness of Bitumen)
Penetrometer → consist of needle assembly with total weight = 100 gm
Unit = 1/10 mm
Grade 80/100 means penetration = 8 - 100mm
More penetration → Less Hardness
No penetration test for Tar as it is softer than bitumen
Airport runway = Grade 30/40
Hot Climate = 30/40, Cold Climate = 80/100
iv. Ring & Ball test
Softening Point @ Temp
Range = 35°C - 70°C
Dia = 0.95cm
Softening point > 40 → if max Temp = 40°
v. Briquette
Ductility → Adhesion & elasticity of bitumen
at 27°C @ 50mm/min
expressed as distance
Range = 50 - 100 cm
acc to ISI min Ductility value = 75 cm for 45 & above.
Ductility → Tar > Bitumen
vi. Solubility test
With trichloroethylene, Purity of bitumen
vii. Float Test
Consistency of Bitumen
viii. Pensky marten's apparatus
Flash & fire point → To know the safe mixing and application temperature values of particular bitumen grade
Min flash point = 175℃
Bituminous/Asphaltic concrete mix
Coarse agg + Fine agg + Filler + Bitumen
Advantage → Durability, imperviousness, load spreading properly, Good skid resistance, Quickly openable to traffic
Considered to be the highest quality construction in the group of black-top roads
Bitumen Emulsion
A liquid containing bitumen in suspension
Use → for Cold Mix, Soil stabilisation desert, Patchup work, Wet/rainy weather
a paint used as a anti-corrosive paint
Bitumen/Tar content = 40-60%
Emulsion → 2 Phase system consist of Two immiscible liquid
Types of Bitumen
i. Plastic Bitumen
Bitumen + thinner + suitable inert filler
Used for filling cracks in masonry structures, stopping leakage.
ii. Residual Bitumen
Obtained as a residue during the distillation of high resin petroleum which is a solid substance at normal temperature
iii. Straight run Bitumen
The bitumen is distilled to a definite viscosity or penetration without further treatment.
iv. Cut back Bitumen
Viscosity ↓es by adding volatile diluents & ↑es fluidity of bitumen,
Solvent used → Kerosene, gasoline, Naphtha
Recommended → for wet & Cold Climate
Used in Road construction & Soil Stabilization.
Types of cutback
i. Slow Curin (SC):
high boiling point gas oil
ii. Medium Curing (MC):
Kerosene or high diesel oil
iii. Rapid Curing (RC):
Naphtha, Gasoline, Petroleum
Penetration value = 80/120
RT-1 → Exceptionally cold weather
RT-4 → Premix in macadam
RT-5 → Grouting , has highest viscosity
MC-2 thicker then MC-1 → But RC-5 & SC-5 will have the same viscosity
Asphalt
Black or brownish black in colour
i. Refined Asphalt:
Bitumen, inorganic & organic matter → 52%, 38% & 10%
ii. Mastic Asphalt
bitumen= 7 - 10 %, it is durable, Damp proof, non inflammable, non absorbent & noiseless
Limestone dust filler material used
iii. Cutback Asphalt
Asphalt = 80%
Pavement Mix Design methods
Marshall, Hveem, Hubbard field method & Smith Triaxial method
i. Marshal method
Design of → Bituminous penetration macadam
Stability → Max load(Kg) carried by specimen (t = 63.5mm, 1200gm) at loading @ 50.8mm/minutes, at 60 ± 1 °C.
Flow → 0.25 mm unit, Deformation = 6mm than flow value = 24 units ( 24 x 0.25 = 6)
Marshall stability for DBM mix → 1050 kg
Bitumen content → Max unit wt, desirable air void and minimum flow
Theoretical G → Gt= 100/(W1/G1+W2/G2+W3/G3+W4/G4)
Bulk G → Gm=W / V.w=Wmould / Vmouldw
% Air voids → Vv=(Gt-Gm)/Gt
Bitumen Vol → Vb=Wb.Gm / Gb
Voids in mineral Aggregate → VMA=Vv+Vb
Voids filled with bitumen → VFB=Vb/VMA
PAVEMENT DESIGN
Pavement → Load bearing & distⁿ component
Wet mix macadam → used for Sub base and base course
Geosynthetics → Separation, reinforcement, drainage and filtration in pavement construction
Roughness index of roads → Expressed as cumulative deformation of surface per horizontal distance
Max legal axle load for highway = 8170 kg
Design Life (IRC)
Flexible Pav → NH, SH, Urban Rd = 20 yr, Other Roads= 15 yr
Rigid Pav (Concrete) > 20 yr all type of road
Major Roads > 20 yr
Daily traffic vol
Concrete pav > 1000 ton
WBM < 2000 ton
Types of pavement
On the basis of Wearing course → Classified as Rigid or flexible pavement
Semi-rigid → Lean concrete base
Composite → Uses both Asphalt & Concrete
Whisper concrete → To provide skid resistance and reduce noise level of road
Soil Subgrade → Top of ground on which Foundation of Road or pavement structure Rests, Top 50cm should be compacted at OMC
Sub Base → Drainage, High level deformation
Base course → NH and SH = 250 mm
Wearing course
Strength, Stability and bearing power of highway depends on subgrade
For modern road subgrade shall be consolidated and compacted with a camber of → 1V : 50H
Fog seal → Used in a regular pavement maintenance activity
GSB → On NH as sub-base and drainage layer
WBM
WBM construction → Spreading coarse agg → Dry rolling → Application of filler → Wet rolling → Application of Screening
WBM Stability → Agg interlocking, Particle friction and cohesion
Binding material in WBM → Stone dust, Crushed aggregate dust
Volume Agg Require = 1.2xLBT
Hill Road
Landslide is common problem in hill road
Cath water drain → Provided parallel to loading the intercept and divert the water from hill slopes
Horizontal alignment → Cost of right of way → in mountainous country
Widening → on the inner side
e= V²/225R
Design speed → NH, SH = 50kmph, Hair pin bend = 20 kmph
Min sight distance = SSD
Transition curve → Spiral
Structure in hill road
Breast wall → Earth to retain from slipping, stability of excavated portion of hillside
Retaining wall → Need to retain fill portion of highway cross section
Check wall → Small retaining str, constructed in series on sloping hill face to check slides
Gabion wall → Breast/retaining/check wall constructed with dry stone masonry encased in wire mesh
Parapet wall → Give protection, psychology and physically while travelling on roads with steep valley slope
Rigidity Factor
RF = CP/TP = 0.7/TP
1 Mpa =1 N/mm²
High pressure Tyre → Tyre in tension & TP > CP
TP → Upper layer, CP → Bottom layers
Tyre pressure influences the quality of surface course
Commercial Vehicles → Gross load > 3 ton
Equivalent single wheel load (ESWL)
at d/2 → P, at 2S → 2P
in case of airport design, we can consider this design
S = centre to centre distance, d = clear distance
Log P' = LogP + X
X = (logZ - log(d/2)) x tanθ
Tanθ = slope = (log2P - logP) / [log2S - log(d/2)]
Log P' = LogP +{ (log2P - logP) / [log2S - log(d/2)]} x [logZ - log(d/2)]
Equivalent axle load factor (EALF) = (axle load / standard axle load)⁴
P1N1 = P2N2, where P = load & N = repetition.
Equivalent axle load factor (EALF)
Used in highway design
EALF=(axle load/std. axle load)4 → Fourth power law
Std. axle load = 80 kN
Vehicle damage factor (VDF)
VDF=eq no of std axle/No of vehicle → Number of standard axles per commercial vehicle
used in CBR method
Pavement Evaluation
Structural evaluation → Plate bearing test, Benkel Beam method
Pavement surface condition evaluation → Bump indicator(unevenness index), Roughometer(Profilometer)
Overlay thickness → CBR method and Benkel beam deflection method
Benkleman beam method
Overlay design by deflection technique, Flexible over flexible pavement/overlay
Evaluation of structural capacity of existing flexible pavement
Measure → Deflection of flexible pavement under moving loads
Large rebound deflection → Weak pavement → Needmore overlay thickness
Overlay thickness → Equivalent to granular material of WBM layer
hmm=550log(Dc/Da)
FLEXIBLE PAVEMENT (IRC-37)
Flexible Pavement generally doesn't have any stress due to changes in Temperature
Benkelman beam deflection method → Flexibility overlay on flexible pavement
Methods of design
1. Empirical methods
Commonly used → for physical properties & strength parameters
min base t = 10cm
GI,CBR, Stabilimeter, Mc-Leod method
2. Semi - Empirical/ semi theoretical
Based on stress-strain function
Triaxial test
3. Theoretical methods (Burmister Method)
Based on mathematical computation
Group index Method
An empirical method based on physical properties of sub-grade soil
Based on → Plasticity index, Liquid limit, % finner passing 75μ sieve
GI = 0.2a + 0.005ac + 0.001bd
GI = 0 - 20
Good subgrade soil = 0 - 1, Fair = 2 - 4, Poor = 5 - 9, Very Poor 10 - 20
Surface course and base course thickness → Function of GI and traffic
Sub Base thickness → Function of GI → Total - base course - surface course thickness
Limitation → Does not considered quality of material used in pavement, Same thickness for poor & good quality material
CBR : California bearing Ratio
More accurate
It is a Laboratory test and Penetration test → Represent Strength, Stability of soil subgrade & Base course material or Pavement materials
Best because → Specification of road material is given
Empirical test, it is not the true representation of Resilient modulus
Surcharge weights are used to stimulate the effect of overlaying pavement
Cylindrical Mould → 150 x 175 mm, Collar = 50 mm, Rate of 1.25mm/minutes
CBR = load carried by specimen/load carried by standard specimen
CBR2.5 mm = P(kg)/1370=(kg/cm2)/70
CBR5.0 mm = P(kg)/2055=(kg/cm2)/105
CBR → Highest of above
CBR at 2.5 mm > CBR at 5.0 mm → Adopt CBR at 2.5mm
CBR at 2.5 mm < CBR at 5.0 mm → Repeat the test if identical result follows than → Adopt CBR at 5.0 mm
Greater CBR → Good material/soil strength or good pavement material
Thickness of payment will be maximum → Soil with CBR = 4%
Tcm=1.75P/CBR%-A/ → CBR < 12 %, A =a2=P/pressure=P/p
Load Parameter → Cumulative standard axles in msa
Limitation → Gives the total thickness which remains the same irrespective of the quality of material used in the component layers
Recommendation for CBR (IRC 37)
In Situ test not suggested for design
involves specification of the road material
Avg of 3 test specimens at same moisture content and same proctor density
4 days soaked → Remoulded sample is used → in dry zone (rain < 50 cm) not soaked
If variation > Permissible limit → Take 6 samples
CBR% and Permissible limit → 0-10 = 3%, 10-30 = 5%, 30-60 = 10%
the top 50 cm of subgrade should be compacted at least up to 95 - 100% of proctor density
Soil/sample should be compacted at OMC to get Proctor Density
No of heavy vehicle for design → A=P(1+r)n+10
MC-Leod method
From plate load test
Tcm=K.log(P/S)
California resistance value method
Tcm=K(TI)(90-R) / C1/5
TI=1.35(EWL)0.11, K=0.166
Stabilometer → R value, Cohesionmeter → C value
Triaxial method
Tcm=(3PXY/2Es)2-a2
Single layer elastic theory → Tcm=(3P/2Es)2-a2
Tyre pressure → p = P/a2=P/A
Design deflection → =0.25 cm
IRC method of design (IRC 37)
msa=365[(1+r)n-1]DAF /r
r = 5% as per IRC
Burminster method (Layered system)
Based on 2 elastic theory
Displacement factor depends on → Ratio of modulus of elasticity of pavement and subgrade layers
∆ = 1.5Pa/E → Flexible
∆ = 1.18Pa/E → Rigid
1.5/1.18 = 1.27, 1.18/1.5 = 0.78
P → kg/m² → tyre pressure (contact pressure)
a → cm → √(Wheel load / Pπ)
Coats in flexible pavement
First coat of surface dressing → Bitumen = 14kg/10m²
Prime coat → Adhesion b/w binder course and wearing course
Tack coat → Ensure bond b/w old and new construction, Over existing bitumen layer, bitumen @0.5kg/m²
Seal coat →
RIGID PAVEMENT (IRC 38 : 2012)
Min grade for RCC highway → M40
Design by Elastic theory
Slab width = 3.5 - 3.75 meters
Reinforcement → Single layer at the middle → in the form of welded wire mesh
Flexural strength of concrete is used in design of plain jointed cc pavement
Use of Reinforcement → To ↓es Cracks, ↓es thickness & no of contractⁿ joint
CC roads are not preferred → High initial cost
Depth of reinforcement below the surface of a concrete pavement = 5 cm
Flexural stressload/Flexural strengthconcrete=0.45 → Allowable number of repetitions of axle load = 4500
Modulus of Subgrade reactⁿ (K)
K = P/0.125 (kg/cm²) → Plate load test
K1a1 = K2a2 → a1
IRC → K 75 cm= 0.5 K30 cm
∆ = 1.18Pa/E → Rigid
Radius of Relative Stiffness (l)
By Westergaards
lcm= [Eh³ / 12k(1-μ²)]1/4
l ∝ h^¾, I↑es → μ↑es
Concrete → E = 3 x 10⁵ kg/cm², μ = 0.15
Equivalent Radius of Resisting Sectⁿ(b)
a > 1.724h → b = a
a < 1.724h → b = 1.6a² + h² - 0.675h
h = Slab thickness, a = Radii of wheel load distⁿ
PSI
PSI=5.41-1.80log(1+SV)-0.9C+P
Wheel stress by westergard
Interior → 0.316P[4log(l/b)+1.069] / h2
Edge → 0.572P[4log(l/b)+0.359] / h2
Corner → 3P[1-(a2/l)0.6] / h2
Critical load
Pickard's formula → Design for corner loading
No warping stress → if Temp = constant
Warping of concrete pavement causes reversal of stresses
Wt. vehicle↑es → FF ↑es → But f↓es
Wet Surface → f ∝ C.A. → frictⁿ New tyre > Old
Dry Surface → f ∝ 1/C.A. → friction Old > New
Critical load Position
Taken as → interior, edge and corner loading
Max stress → Summer midday → at edge
Critical stress/load → Day = Edge, Night = Corner
Summer midday → At Edge = Load + Warping - Friction
Winter midday → At Edge = Load + Warping + Friction
Midnight → At Corner = Load + Warping
Goldbecks formula
Tpavement= 3W/σ max
Stress due to corner load =3p/h2
JOINTS
i. Expansion joint
Transverse direction → Temp rise and fall, Subgrade moisture variation
Max spacing = 140 mm → Interval = 25 - 30 m
Width or thickness = 2.5 cm
Max distance b/w EJ = 45 m
ii. Contraction joint
Transverse direction → Shrinkage & moisture variation
Provide → Where BM & SF is small & member is supported by other matter
At distance of 10 meters
Primarily relieves tensile stress in a concrete pavements
CJ is Predefined location of crack in a cc pavement
f = 1.5
Dowel bars
Provided at Transverse joint → Extension and contraction joint → Along direction of traffic
Load transfer from one slab to another & Keep slab at same height
Load transfer capacity = 40% of wheel load
Ht. above the road level = 30 cm
iii. Warping/hinged joint
Along longitudinal section direction to prevent spilling of concrete due to temperature and subgrade Moisture variation
Relieve warping stress & Rarely needed
iv. Construction
Shouldn't provided at corner
v. Longitudinal joint
Along the length of pavement to ↓es warping stress
Butt type in concrete pavement → IRC recommendation
Provided with tie bar
Tie bar length = 2 x development length (Ld) + Gap
Ld = σ st ϕ / 4 τ bd → ϕ ≈ 10mm
Tie bar → Firmly tie longitudinally adjacent slabs
DEFECTS
Grading → Flattening and smoothing the road surface by scraping
Sympathetic crack → Brittleness due to ageing of binder
Bituminous emulsion → Best binder material for stone aggregate, in patch repair work during rainy season with heavy traffic
Bird Baths
localised pavement surface areas with slightly lower elevation than surrounding pavements, it is due to subgrade failure
Subsidence
localised/Abrupt lowering of the road surface , it may result from poorly compacted bad fill, poor local drainage
Defects of rigid pavements (Concrete)
Scaling of cement concrete
Shrinkage cracks → Joints and cracks on pavement layers
Warping cracks
Mud Pumping → Ejection of soil slurry, Due to stagnation of water and hence softening of clayey subgrade
Spalling of joints
Structural cracks
Defects of Flexible Pavement (Bituminous)
Much failure in foundation layers → Base course failure
Rate of deterioration → Exponential
i. Surface defects
Fatty surface: bituminous binder moves upwards
Streaking →
ii.Cracking
Hairline cracks → Short & fine cracks at short interval
Alligator/Map cracking(Crazing) → Random deep Cracks, fatigue arising from repeated stress application, network of minor cracks on pavement Slab, Relative movement of pavement layer, repeated application of heavy wheel loads, Swelling and shrinkage of subgrade or other layers due to moisture variation, Brittleness and overheating of bitumen
Reflecting cracking → Bituminous overlay over cement concrete surface
Edge cracking →
Hairline crack → insufficient bitumen content
iii. Disintegration
Stripping → Separation due to poor bitumen adhesion, Due to moisture damage, Segregation of bitumen and aggregate in the presence of moisture
Pothole → Bowl shaped holes extending into base course, progressive disintegration of bituminous premix
Ravelling → Removals of large surface aggregate leaving craters, Progressive large disintegration of surface, caused by use of open graded aggregate
Loss of aggregate →
iv. Deformation
Rutting → Longitudinal depression on surface due to repeated application of load along the same wheel path, consolidation of one or more layer, Due to inadequate compaction of pav layers
Shallow depression: size nearly 25mm
- Corrugation: regular undulations
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