This document provides an overview of traffic engineering, including its definition, scope, and key areas of focus. Traffic engineering is a branch of civil engineering that deals with the safe and efficient movement of people and goods on roadways. It involves the study of traffic characteristics, operations, planning and analysis, geometric design, administration and management, and road safety. Some key aspects covered include traffic flow parameters like speed, volume, and density; vehicle characteristics; and methods for conducting traffic studies to analyze volume, speed, accidents, and other metrics. The goal of traffic engineering is to achieve efficient traffic flow with the lowest number of accidents.

1. 2CI 703 – Highway & Traffic
Engineering
“Traffic
Engineering”

2. What Is Traffic Engineering?
✓ Traffic Engineering is a branch of Civil Engineering
which deals with the Safe & Efficient movement of
people & goods on road ways.
✓Institute of Traffic Engineering, U.S.A. defines, “ Traffic
engineering is that phase of engineering which deals with
planning and geometric design of Streets, Highways,
abutting lands and with traffic operation thereon, as their
use is related to the safe, convenient & economic
transportation of persons & Goods”.

3. ✓Traffic Engineering is that branch of engineering which
deals with the improvement of traffic performance of
road network & terminals.
✓This is achieved by systematic traffic studies. Scientific
analysis & engineering application.
✓This method includes planning & geometric design on the
one hand and regulation and control on the other.
✓Traffic engineering therefore deals with the application of
scientific principles, tools, techniques & finding for safe,
rapid, convenient & economic movement of people &
goods.

4. ✓Traffic engineering focuses on the construction of
infrastructure which necessary for movement of people &
goods with good level of service, safe, economic,
sustainable & environmentally safe.
✓Movement of People & goods from one place to other
place involve many activities like purpose of movement,
time for movement, mode for movement.

5. ❑ Scope of Traffic Engineering:
✓The basic object of Traffic engineering is to achieve
efficient free & rapid flow of traffic, with least number of
traffic accident.
✓Actual studies of traffic operations provide the foundation
for developing methods for improvement in general & for
solving specific problems.
✓The study of traffic engineering divided into seven
major section:
✓Traffic Characteristics
✓Traffic studies & Analysis
✓Traffic operation- control & Regulation
✓Planning & analysis
✓Geometric design
✓Administration & Management
✓Road safety Aspect

6. ✓Studies of Traffic characteristic is the most essential
prerequisite for any improvement of traffic facilities.
✓The traffic characteristics are quite complex with various
types of road users in the road moving with different
motives.
✓The study of vehicular characteristics is an essential part .
Apart form these the various studies to be carried out on
the actual traffic include speed, volume, capacity, travel
pattern, origin & destination, traffic flow characteristics,
parking & accident studies.
✓Various aspects that are covered under traffic operations
are regulations, control and the warrants for application of
controls.

7. ✓Regulations may be in the form of laws & ordinances or
other traffic regulatory measures such as speed limits etc.
✓Installation of Traffic control devices like signs, signals &
islands are most common means to regulate & control
traffic.
✓Traffic planning is a separate phase for major highways
like express way, arterial road, mass transit facilities &
parking facilities.
✓All the aspects such as cross section & surface details,
sight distance requirement, horizontal & vertical
alignment, intersections & parking facilities are to be
suitably design for better performance.

8. ✓The various phase of traffic engineering are implemented
with the help of “Engineering, Enforcement &
Education” or “3-Es”.
✓Enforcement is usually made through traffic laws,
regulation & control.
✓Education is possible by sufficient publicity & through
schools and television. It aims at improving the human
improved traffic performance.
✓Engineering phase is the one which is constructive. This
phase deals with improvement of road geometrics,
providing additional road facilities & installation of
suitably designed traffic control devices.

9. ❑ TRAFFIC CHARACTERISTICS
✓Traffic Engineering deals with three elements:
✓Road User Characteristics (Drive, Passenger &
pedestrian)
✓Vehicle Characteristics (Vehicle used for the movement)
✓Road (Type of road & its geometry)
✓It is very essential to know the characteristics of all these
three elements for the traffic engineering to make efficient
management & planning of traffic flow.

10. ❑ ROAD USER CHARACTERISTIC
✓ Road user is the person who uses the road being
pedestrian, bicyclists, driver or passenger.
✓This is the part deals directly with human behavior and
needs to consider varying situation, time, age of the
person, decision making etc.
✓The physical, mental and emotional characteristics of
human being affects their ability to operate motor vehicle
safety or as a pedestrian.
✓Hence the importance to the traffic engineer to study the
characteristics & limitations of the road users.

11. ✓ The various factors which affect human characteristics as road
users may broadly classified under four heads:
✓Physical (Vision, Hearing)
✓Mental (Knowledge, Intelligence)
✓Psychological (Fear, Anger)
✓Environmental (Weather Condition)
✓Physical Characteristics :
i. Visual Factors
ii. Hearing
iii. Strength
iv. Judgment Power
v. Reaction Time

12. ✓ Vision plays the most important role of all these. These
include the acuity of vision, peripheral vision, eye movement
& depth judgment.
✓Glare vision & glare recovery times of drivers play important
during night.
✓Minimum standard for acuity of vision are often laid down by
licensing authority.
✓The vision is fairly satisfactory up to 10 in general & even up
to 20 in the horizontal plane.
✓As the filed of clear vision is limited, the road users have to
often shift their eyes within the peripheral field to obtain clear
vision.

13. ✓ Eye vision:

14. ✓ The total time taken for the eye movement depends in
some of the physical characteristics including the
response.
✓The depth of judgment is important for a driver in
judging distance & speed of vehicles & other object
ahead.
✓The effects of glare, adoptability to changes of light i.e.,
darkness to light & bright light to darkness, should also
be studied.
✓Hearing helps driver in a way, though it is more important
factor for pedestrian & cyclists.

15. ✓ Though strength is not an important factor in general
lack of strength may make parking maneuvers difficult,
particularly for heavy vehicles.
✓The reaction to traffic situation depends on the time
required to perceive & understand the traffic situation &
to take appropriate action.

16. ✓ Temporary Physical Factors:
i. Alcohol
ii. Fatigue
iii. Illness
iv. Anger
v. Climatic Factors
✓ Psychological factors
i. Motivations
ii. Intelligence
iii. Learning
iv. Emotion
v. PIEV time (Reaction Time)

17. ✓ Temporary Physical factors
✓Alcohol affects on the physical & mental ability to drive.
It produces poor attention, less self control, slower
response of the driver & late reaction time.
✓Fatigue (Tired) produces sleepiness & reduces the
judgment capacity & increase reaction time.
✓If road user having illness or any disease, it results into
slower reaction time.
✓Anger effects on the mental stability. It affects on
judgment capacity & reaction time.
✓Climatic factors include seasonal change, time of travel,
altitude, light & other psychological effects.

18. ✓ Psychological factors
✓Motivation : The purpose of travel affects on the behavior
of the driver. If purpose of travel is to save money, time
etc. it may lead to violation of safety norms.
✓Intelligence : The capacity of the road user depends on
the awareness of the traffic & adjustment to the situation.
✓Learning : It depends on habits, skills, motivation,
intelligence etc. road user may learn from the past study
& behave accordingly.
✓Emotion : In includes fear, anger, worry, behavior, logic
etc. it affects directly on the behavior of road users.

19. ✓ PIEV time: it is time required to response. It is
summation of Perception, Intellection, Emotion &
Volition time.
✓Perception: It is the time required to perceive an object or
situation.
✓Intellection: It is the time required for understanding the
situation. It also included the comparison of different
thoughts & new sensations.
✓Emotion: It is time in which the emotion & disturbances
such as anger, fear etc. produces with reference to situation.
✓Volition: It is time taken for the action.
✓Total reaction time of an average driver is 3 to 4 seconds. It
may increase depend on Age complexity, depending on the
situation.

20. ✓ Factors affecting PIEV:
✓Age
✓Fatigue
✓Complexity of Reactions
✓Presence of Drugs or Alcohol
✓For braking reaction on Highways
✓Perception & Reaction time: 2.5 seconds
✓For reaction time to traffic Signal
✓Pedestrian Factors: Pedestrian walking speeds ranges from
1 to 1.5 m per seconds & their reaction time ranges from 4.0 to
5.0 seconds. It depends in Age, mental, physical & emotional
characteristics of pedestrian and traffic & Road condition.

21. Vehicle Characteristics
✓ Vehicle is an important element of traffic engineering.
Traffic flow behavior depend on the type of vehicle & its
characteristics.
✓Vehicle characteristics can be classified in physical &
operating characteristics. This is useful for geometric &
pavement design of highway.
✓Physical Characteristics:
✓Traffic stream consist of motorized & non motorized
vehicles with the different weights & dimension in
developing country.

22. ✓ Type of vehicle
✓In India Heterogeneous traffic is observed. It is a combination of
fast moving & slow moving vehicles.
✓Fast Moving vehicle : it includes truck, buses, luxury, jeeps, cars,
auto rickshaw, scooters, bikes & other transport vehicles.
✓Slow Moving vehicle : It includes bullock cart, cycles, man pulled
rickshaw etc.
✓Dimensions :
✓Dimensions of the vehicles are having much importance in the
geometric design of the road.
✓Length :
✓It affects on Horizontal alignment, minimum turning radius, extra
widening of curve, passing sight distance capacity of the road &
Parking space.
✓The length of single unit with two axle vehicle is 10.7 m.
✓The maximum permissible length is 9.5 m to 18.0 m.

23. ✓ Width:
✓It affects on lane width, width of shoulders, width of parking
lots, etc. the maximum permissible value of width is 2.44 m
for motor vehicle to 2.7 for transport vehicle.
✓Weight:
✓It affects on pavement thickness, gradient, super elevation.
✓As per IRC specification, the maximum permissible load of
single axle vehicle is 8165kg, the gross weight of the vehicle
can be found out by using the equation.
✓𝑊 = [465(24 + 3.28𝐿) − 1.46𝐿2
]
✓Where W= Gross weight of vehicle in kg
✓L= Distance between the axle in m.

24. ✓Vehicle Dimension

25. ✓ Height :
✓It affects on the clearance to be provided under bridges, sub
ways & services lines etc. Maximum permissible height is
varying from 3.8 m to 4.75 m for double decked motor vehicle.
✓ Turning Radius :
✓The minimum turning radius of slow speed vehicles depend
upon the wheel base & steering angle. For high speed vehicles,
turning radius is controlled by super elevation & side friction. It
affects on the parking maneuver, curves etc.
✓ Speed of Vehicle :
✓ The vehicle speed affects (i) Sight Distance (ii) super
elevation, length of transition curve & limiting radius on
horizontal curves (iii) Length of transition curves on vertical
valley curves & on humps. (iv) Width of pavement &
shoulders on straight & horizontal curves (v) Design gradient
(vi) capacity of traffic lane (vii) design & control measures on
intersections.

26. Maximum dimension on Road vehicles:
Dim. of Vehicle Details Maxi. Dim. (m)
Width All vehicles 2.50
Height
(a) Single –decked vehicle for
normal application
3.80
(b) Double – decked vehicle 4.75
Length
(a) Single unit truck with two or
more axle
11.00
(b) Single unit bus with two or
more axle
12.00
(c) Semi trailer tractor
combination
16.00
(d) Tractor & tailor combination 18.00

27. ✓ Braking Characteristics:
✓The deceleration & braking characteristics of vehicles
depend on the design & type of braking system & its
efficiency.
✓The safety of vehicle operation, stopping distance & the
spacing between the two consecutive vehicles in a traffic
stream are affected by the braking capacity.
✓Thus the highway capacity & overtaking sight distance
requirements also indirectly get affected.
✓At least two of the following three measurements are
needed during the braking tests in order to determine the
skid resistance of the pavement.
✓(i) Braking Distance, L meters
✓(ii) Initial speed, u m/sec
✓(iii) Actual duration of brake application, t seconds.

28. ✓ Head Light of vehicle:
✓This will be useful for vertical curve design & design of sign
board for night visibility.

29. Traffic Flow Characteristic:
✓The traffic engineers are connected with the flow of group of
vehicles on the highway system for planning, designing &
operation plans.
✓The characteristics of traffic flow are influenced by type of road
& the vehicle super operating characteristics.
✓There are three basic flow of parameter of traffic. These
parameter are inter connected.
✓Speed
✓Volume/flow
✓Density

30. ✓Speed: It is the distance travelled per unit time. It is expressed
in km/hour.
✓Spot speed : It is a speed of vehicle at any spot on a highway.
✓Time mean speed : It is a arithmetic mean of the speeds of all
traffic passing at a specific point. It is also known as average
spot speed.
✓Running speed : It is the speed of the vehicles over a specified
stretch, it is distance travelled divided by running time.
✓Design speed : It is the maximum safe speed maintained over
the specified section under ideal conditions of weather, traffic
& geometric design.

31. ✓Modal Speed : When all the speed data are arranged in
ascending order, the middle speed value is called Modal speed.
It is the 50th Percentile speed.
✓Operating Speed : It is the highest speed at which driver can
travel under existing condition without any exceeding design
speed.
✓Space mean speed : It is the speed corresponding to the
average of overall travel time to pass the specified section of
road.

32. ✓Volume/Flow : It is the number of vehicle passing a given
point during the specified period of time. It is expressed as
vehicle/ Hour.
✓Density : It is the number of vehicle occupying the a unit
length of the lane of the roadway at a given instant, it is
expressed as vehicles/km/lane.
✓Space head way : It is the distance form head to head of
successive vehicles.
✓Time headway : It is the time interval between head to head of
successive vehicles passing given point measured from front to
front of the vehicles.

33. ✓Purpose of spot speed survey :
✓To establish the tends in speed of vehicles.
✓To get the speed data for traffic regulation works.
✓To establish the speed limits in cities.
✓To locate the speed breaker.
✓To locate the traffic sign.
✓To determine the hazardous spots in a cities.
✓To determine the design speed of the vehicles.
✓To determine the super elevation, sight distance etc.

34. ✓ Traffic Volume studies:
✓ Traffic volume study is important in traffic planning,
designing, operation & research. Traffic volume data are used
for
▪ Establishing trends in traffic volume
▪ Calculating an accident rate per vehicles km
▪ Designing of traffic elements
▪ Geometric design of the roads
▪ Calculating a capacity of roads
▪ Justifying the control devices such as signals.

35. ✓ Methods of Traffic volume count
✓ Manual Count
✓ Mechanical Methods
✓ Electric contact device
✓ Radar device
✓ Magnetic device
✓ Pneumatic detector
✓ Photographic Method
✓ Videography Method.

36. ✓ Manual Count :
✓ It is a simplest method of counting. An observer count the
vehicles passes a fixed point on a road. Manual counting can
be done using hand tallies – a device which is pressed &
rotates the number increases by one.
✓ The total number of vehicles at the end of each counting
period is obtained. It is not suitable for bad weather.
✓ Electric contact device :
✓ It consist sub surface detector. It provides positive contact
for each vehicle crossing through it. A steel plate over which
rubber pad is provided to hold suspended strips.

37. ✓ Radar device :
✓ Vehicle is detected continuously by comparing the
frequency transmitted radio signal with frequency of the
reflected signal. If the vehicles passes through lane,
frequency difference occurs.
✓Photographic Method :
✓ It involves the continuous strip photographs from airplane
over the stretch. Based on the principles of photogrammetry,
the relation ship of volume, speed 7 other parameters are
evaluated.

38. ✓ Videography method :
✓ The videography is carried out for the stretch of road about
20 -30 m. the entry & exit of the vehicle on the selected
approach should be covered in the videography. The start
time of the video is set to Zero.
✓ The movement of the vehicles are recorded for an hour.
After the end of the videography, the vehicles are counted on
the screen of the computer of DVD.
✓ The entry time of the vehicles & exit time of the vehicle is
recorded for the vehicles on the selected approach, the
distance passed by the vehicle per unit time is worked out.

39. ✓Passenger Car Unit (PCU)
✓ All the vehicles are having wide range of characteristics like
length, width, height, power, speed, acceleration etc.in our
country, such type of mixed traffic moves.
✓ It is difficult to estimate traffic volume & capacity of road
way.
✓ The passenger car is considered as standard vehicle unit to
convert the other vehicle classes. This unit is called
Passenger Car Units (PCU).

40. PCU values as per IRC:106-1990 (For Urban Area)
Sr.No. Vehicle Type
Equivalent PCU factors %
composition of vehicle type in
traffic stream
5% 10% and More
1
Two wheelers, Motor
cycle or scooter
0.5 0.75
2
Passenger car, pick up
van
1.0 1.0
3 Auto rickshaw 1.2 2.0
4 LCV 1.4 2.0
5 Truck or Bus 2.2 3.7
6 Tractor Trailer 4.0 5.0
7 Cycle 0.4 0.5
8 Hand Cart 2.0 3.0

41. PCU values as per IRC:64-1990 (For Rural Area)
Sr.No. Vehicle Type
Equivalent
Factors
1
Two wheelers, Motor
cycle or scooter
0.5
2
Passenger car, pick up
van
1.0
3 Tractor, LCV 1.5
4 Truck or bus 3.0
5 Cycle 0.5
6 Cycle-rickshaw 2.0
7 Hand cart 3.0
8 Bullock cart 8.0

42. PARKING STUDIES:
✓ Cities are developing tremendously. Production of vehicles &
ownership of all types of vehicles increases.
✓ It is mandatory to provide parking area for the vehicles. It is
important to study about the parking area & its requirements.
✓ We need to understand the terminology used in parking
study:
✓ Parking Accumulation : It is the total number of vehicles
parked in the defined area at a specified time.
✓ Parking Volume : It is the number of vehicles parked in a
specified area over given period of time. It is measured in
vehicles/day.
✓ Parking Load : It is total number of parking space hours used
by the vehicle during a given period of time.

43. ✓ Parking Duration : It is the average time spent in a parking
space.
✓ Turn Over : It is average number of times a parking space is
used by vehicles during a given period of time.
✓ Purpose of Parking Study:
✓ To determine the supply & demand of the parking facilities.
✓ To know the purpose of parking facilities.
✓ To determine the demand for parking space.
✓ To finalize the location of parking area.
✓ To study legal, financial & administrative factors related to
parking area.

44. Types of Parking Survey :
✓ Inventory of parking space
✓ Parking usage survey
✓ Questionnaires type parking space survey
✓ Cordon Count
Inventory of Parking :
✓ In this method, the details of existing facilities such as lanes,
streets, kerb etc. are located. The data includes the location,
capacity & features of the surrounding area. All data are
summarized & planning is made accordingly.
Parking Usage Survey :
✓ In this method, the whole study area is divided into blocks,
actual parking space utilized is recorded. The time for which
the vehicle is parked are recorded. The inventory of both on
street parking & off street parking is recorded.

45. Questionnaire type Parking space survey:
✓ In this method, the vehicle users are asked to give the details of
his origin, destination, journey time, parking fees expected,
parking space availability, time of arrival & departure from
parking etc. based on the data collected, the demand & supply
of the parking is worked out. The planning of the parking is
done.
Cordon Count :
✓ In this method, the counting of vehicles coming in or going out
from the street & crossing of the study area are recorded. It is
carried out to determine the volume, classification of traffic,
parking load etc.

46. Types Of Parking:
On Street Parking
Off Street Parking
✓ On Street Parking:
The following are the types of
on Street Parking
✓ Parallel parking
✓ 30 Angle parking
✓ 45 Angle Parking
✓ 60 Angle Parking
✓ Right Angle Parking
✓ Off Street Parking
The following are the types of
Off Street Parking
✓ Surface Parking
✓ Multi Storey Parking
✓ Roof Parking
✓ Mechanical Parking
✓ Under Ground Parking

47. Types of On Street Parking

48. Accident Studies:
✓ Road accidents can be classified as:
✓ Fatal
✓ Major
✓ Minor & Property damage
✓ Fatal : The victim of accident is dead on the spot.
✓ Major : The victim of the accident is hospitalized for more
than 48 hours.
✓ Minor : The victim of the accident goes to his work
immediately after getting first aid treatment.

49. Purpose of Accident Studies:
✓ To identify the accident prone zone in the city.
✓ To improve the geometric design of the accident prone zone.
✓ To calculate the financial losses of accidents.
✓ To create the awareness about the safety in road users.
✓ To give the data of accident to the planning stage to consider
the suggestion.
Causes of An Accident:
Accident occurred on road due to combination of several factors
like unsafe driving or walking, bad whether etc. following are
the causes of accidents.
✓ Due to the Driver : Excess speed, violating the rules, fatigue,
sleep, alcohol etc.
✓ Due to pedestrian : Carelessness, Illiteracy, crossing of the
road at wrong location etc.

50. ✓ Due to Passenger : Causing inattention of drivers by talking &
joking, projecting part of the body out side.
✓ Vehicles : Due to tyre burst, failure of brakes, improper
lighting or other mechanical factors.
✓ Condition of Roads : Slippery surface, improper surface, pot
holes, damaged roads.
✓ Road Design : improper geometric design, improper cross
slope, improper super elevation, improper design of curves etc.
✓ Weather Conditions : Rainy season, snow fall, dust, improper
visibility.

51. COLLISION DIAGRAM :
✓ It is a pictorial representation of different types of accidents
occurred at the Intersection.
✓ It is useful to display & identify the accident patterns.
✓ It is helpful for studying the accident pattern on Particular
intersection.
✓ It provides the information on the type & number of
accidents, including condition such as time of day, day of
week, climatic conditions, pavement conditions & other
information critical to determining the causes of safety
problems.

52. ✓ The collision diagram includes the following
information:
✓ Period of Observation
✓ Direction of vehicle movement
✓ Availability of fixed project
✓ Position of vehicles at the time of accident
✓ Head on collision
✓ Rear End collision
✓ Types of collision like right angle collision, right turn
collision
✓ The Collision diagram is prepared for equal periods. After
the proper study of collision diagram, the corrective
measures can be planned.

53. Collision Diagram

54. Condition Diagram :
✓ The object of the condition diagram is to show the
intersection & the condition within the surrounding area as
it axis.
✓ The condition diagram is the pictorial presentation of
physical condition present at the intersection under study.
✓ The required visibility for the 85th percentile speed on the
road & the actual visibility triangle are determined from the
condition diagram.

55. Condition Diagram :

56. Condition Diagram includes the following
information :
✓ North Direction
✓ Pavement edges, kerb & shoulders
✓ Width of Road
✓ Existing parking condition
✓ Bus stops
✓ Availability of existing lightning poles
✓ Trees
✓ Signs
✓ Fences or Compound walls
✓ Existing building
✓ Distance to adjacent traffic signal
✓ Pavement marking
✓ Cycle track

57. Preventive measures for Accidents:
✓ Geometric aspects like road width, alignment & design of
intersection should be properly done. Provision of bye pass,
fly overs etc. may help in prevention of accident.
✓ All vehicle of public services & goods movement should be
maintained properly.
✓ Provisions of adequate lighting system on road may help in
prevention of accidents.
✓ Excessive speed is the prime factors for accident. Speed
breakers should be properly provided.

58. ✓ Traffic control devices like sign, marking, signal etc. should
be appropriately provided.
✓ Before issuing license, visibility, reaction time & other
medical test should be conducted for drivers.
✓ Exclusive lane for pedestrian & cyclist should be provided.
✓ Pedestrian, drivers & other road users should be properly
trained through film, slides, poster etc.

59. Conflict at Two-Way Traffic

60. Traffic Control Devices:
Traffic Control devices are classified as shown below:
Traffic Control Devices
Signs
Regulatory
Warnings
Informatory
Markings
Pavement
Kerb
Object
Reflectors
Signals
Fixed Time
Manually
Operated
Pedestrian
Special Traffic
Islands
Divisional
Channelizing
Rotary
Pedestrian
Loading
Lights

61. ✓ The devices used to control, regulate & guide traffic is
called traffic control devices.
Traffic Sign :
✓ Traffic sign is a device mounted on a fixed or portable
support whereby a specific message is conveyed by means
of words or symbol officially erected for the purpose of
regulating, warning or informing traffic.
✓ Size of Sign : The recommended sizes for the traffic sign
are shown in Table. The normal size is used in important
roads & smaller size is used in less important roads. On
expressways, bigger than normal sizes may be used.
✓ Colour of signs should be as shown detail drawing IRC:67.

62. Size of Sign Boards
Sign Normal size (cm) Small Size (cm)
Mandatory: Stop Sign
(Octagonal)
90 60
Mandatory: Give way
(Inverted Triangle)
90 (Side) 60
Mandatory : Other
(Circular)
90 (Dia) 60 (Dia)
Warning (Triangular) 90 (Side) 60 (Side)
Informatory
(Rectangular)
80 *60 60

63. ✓ Regulatory or Mandatory Sign are mean to inform the road
user of certain laws, regulation & prohibition. The violation of
this sign is the legal offence. The regulatory signs are
classified under the following sub heads:
✓ Stop and Give-way signs
✓ Prohibition signs
✓ No Parking & No Stopping signs
✓ Speed limit & Vehicle Control Signs
✓ Restriction Ends Sign
✓ Compulsory Direction control & other signs
✓ This sign is white Colour with a red border.
✓ The No Stopping/standing sign is circular in shape with blue
back ground, red border & two oblique red bars at 45 & right
angle to each other.

64. ✓ Regulatory or Mandatory Sign

65. ✓ Warning Sign are used to warn the road users of certain
hazardous condition that exist on or adjacent to the roadway.
✓ The warning signs are in the shape of equilateral triangle with
its apex pointing upward. They have white background, red
border & black symbol.
✓ The warning signs are to be located at sufficient distance in
advance of the hazard warned against; this distance are
120,90,60 & 40 m respectively on National/State Highway,
MDR, ODR & VR on urban roads this distance is 50 m.
✓ The commonly used warning signs are Right Hand/Left hand
curve, Steep Ascent/Descent, Narrow bridge/Road Ahead, Gap
in Median, Slippery Road, Cycle crossing, Pedestrian
Crossing, School Zone, Unguarded Railway Crossing,
Guarded Railway Crossing.

66. ✓ Warning Sign are used

67. ✓ Informatory Sign are used to guide the road users along the
travel route to make travel easier, safe & pleasant. These sign
inform to road user the name of highway, distances & the
direction of the places & other amenities like hotels, fuel pump
etc.
✓ The direction & place information signs are rectangular with
white back ground, black border & black arrow & letters.
✓ The facility information signs are rectangular with blue back
ground & white/black letters/symbols. Some of these sign
indicate public telephone, petrol pump, hospital, eating place.

68. Informatory Sign

69. Road Marking
✓ Marking on the road carriageway & on the object within an
adjacent to roadways are used as means to guiding &
controlling the traffic.
✓ They promote road safety & ensure smooth flow of traffic in
to the required direction or path of travel.
✓ The marking are made by white, black & yellow colors
paints. Use these colors are for specific marking applications.
✓ Yellow marking are used to indicate parking restriction,
continuous Centre line & barrier line marking.
✓ White colors marking provide at intersection for pedestrian
crossing.
✓ The night visibility is improved by the use of minute glass
beads embedded in the pavement marking material to produce
a retro reflective surface.

70. ✓ Types of Road Marking
✓ Longitudinal Lines:
✓ These line markings are used as
✓ Lane lines – To separate the lanes
✓ Barrier Lines – To keep the distance from vehicle
✓ Separation line – Single broken line
✓ Guide lines –To guide the driver about the lane
✓ Continuity line – To show the continuity of lane
✓ Edge line –To show the edge of the lane on road
✓ Centre line –To show the Centre of the road

71. Transverse Lines:
✓ Stop Line – To show the stop vehicle
✓ Holding Line – To show the safe position for vehicle to be held
✓ Zebra crossing Line – To permit the pedestrian for crossing the
road
✓ Other Marking :
✓ Turn Lines – To guide the vehicles during turning
✓ Give way Lines – To give way to vehicles at the entrance of
the intersection
✓ Parking control Line – Normally yellow in colors for
temporary parking on road.

72. Road Marking

73. Traffic Signal
✓ Signal is a device provided at intersection to control the traffic.
✓ It provides for orderly movement of vehicle, reduces the
frequency of accidents & warns & control the traffic.
✓ It may be operated manually, electrically or mechanically.
✓ Signal shows the RED, GREEN & YELLOW.
✓ Red Indicates – Vehicle must STOP
✓ Green Indicates – Vehicle Can GO
✓ Yellow/Amber Indicates – Light is going to Change, It varies
from 2 to 4 seconds

74. Traffic Signal

75. ✓Types of Traffic Signal
✓ Fixed Time Signals
✓ Vehicle actuated Signal
✓ Pedestrian Signal
✓ Flashing Signal
✓ Bus Priority Signal
✓ Fixed Time Signal : The time Period for each phase is fixed.
The signal indicates Red-Green-Yellow light at fixed interval
for each phase.
✓ In this system, traffic flow & its fluctuation is not considered.
The cycle length may very from 40 to 120 seconds.
✓ This type of signal is cheap & easy to install & Maintain.

76. ✓ Vehicle Actuated Signal : In this type of signal system, the
signal timing are changed according to the actual traffic
volume on each leg of the intersection.
✓ The detecting devices are placed into the Road. Vehicle is
recorded as it crosses the detector.
✓ Signal are automatically adjusted as per the timing interval
between the vehicles on the leg.
✓ This type of signal are useful when traffic flow at the
intersection varies on term basis.
✓ Bus Priority Signal : This type of signal is provided, where
the priority is to be given to public transport. When there is bus
in the traffic stream, signal indicates ‘Green’ to the bus lane to
reduce the delay to Passengers.

77. ✓ Pedestrian Signal : In the busy traffic area, signals are
provided for crossing the roads by pedestrians.
✓ The signals indicates “Red” light for traffic to stop & permit
the pedestrian to cross the intersection.
✓ Flashing Signal : Some times “Yellow flashing signals are
provided on the main road” & “Red flashing signals are
provided to warn the drivers”. It indicates slow down the
vehicles & proceed with caution.
✓ This type of signals are provided at sharp horizontal curves,
Railway crossing & other important cross roads.

78. ✓ One Way streets :
✓ In congested streets one of the methods to reduce accidents &
to ensure smooth flow of traffic along one way street.
✓ The traffic is allowed to move only in one specified direction.
✓ The main advantages of one way streets may be greater
capacity, increased average speed, improved pedestrians
movement & reduction in accident.
✓ The various types of conflict at an intersection are
✓ Crossing Conflicts
✓ Merging Conflicts
✓ Diverging Conflicts

80. Various Types of Intersection :
✓ An intersection is a Junction on a road where two or more
roads either meet or cross at grade.
✓ Intersection may be 3-leg, 4-leg, 5-leg as per the number of
roads meet at particular junction.
✓ This junction controlled by providing traffic lights & may be
roundabout.
✓ The intersection further classified as un-controlled &
controlled.
✓ An Uncontrolled intersection is where no traffic light or signs
are used to indicate the right of way.
✓ Controlled intersection is where signal or other means to
indicate the Right-of-way.

81. ✓ Intersection are classified under two broad heads namely, At-
Grade & Grade Separated.
✓ In grade separated intersection, one or more crossing conflicts
are reduced by over bridge or under pass.
✓ At grade & Grade separated intersections may be sub-divided:
✓ By shape : “T”, “Y”, scissor, cross staggered.
✓ By separation of travel Path : Channelized Intersection.
✓ By type of Control : Uncontrolled & Priority controlled.
✓ By conversion of crossing into weaving maneuver : Rotary or
Roundabout.
✓ By separation in time : Signal controlled.
✓ By space separation : Grade separation: Flyover, Road over
bridges, Road under bridges, Interchanges.

82. ✓ Types Of Intersection

83. ✓ At Grade Intersection :
✓ All road intersections which meet at about the same level
allowing traffic maneuvers like merging, diverging, crossing &
weaving are called at grade intersection.
✓ These intersection classified as unchannelized, channelized &
rotary intersection.

84. ✓ At Grade Intersection :

85. ✓ Basic Requirements of Intersection At Grade are:
✓ At the intersection the area of conflict should be as small as
possible.
✓ Sudden change of path should be avoided.
✓ Adequate visibility should be available for vehicles
approaching intersection.
✓ Geometric features like turning radius & width of pavement
should be adequate provided.
✓ Proper sign should be provided on the road approaching
intersection to warn the drivers.
✓ Good lightning at night is desirable.
✓ If the number of pedestrians & cyclist are large separate
provision should be made for their safe passage in intersection
with high volume of fast moving traffic.

86. ✓ Grade Separated Intersection :
✓ The intersecting roads are separated by difference in level, thus
eliminating the crossing maneuvers.
✓ Grade separated intersection design is the highest form of
intersection treatment. This type of intersection causes least
delay & hazard to the crossing traffic & in general is much
superior to intersection at grade from the point of view of
traffic safety & efficient operation.
✓ A highway grade separation is achieved by means of vertical
level.

87. ✓ Grade Separated Intersection :

88. ✓ Advantages of Grade Separation :
✓ Maximum facility is given to the crossing traffic. As the roads
are separate, this avoids necessity of stopping & avoid accident
while crossing.
✓ There is overall increase in comfort & convenience to the
motorists & saving in travel time & vehicle operating cost.
✓ Grade separation is an essential part of controlled access
highway like expressway & freeway.
✓ It is possible to adopt grade separation for all likely angles &
layout of intersecting roads.

89. ✓ Presentation on Spot speed data:
(a) Average speed of vehicles: From the spot speed data of the
selected samples, frequency distribution tables are prepared
by arranging the data in group covering various speed ranges
& the number of vehicles in such range.
✓ The arithmetic mean is taken as the average speed. The table
gives the general information of the speeds maintained on the
section & also regarding the speed distribution pattern.
(b) Cumulative speed of vehicles : A graph is plotted with the
average values such of each speed group on the X-axis & the
cumulative percent of vehicles travelled at or below the different
speed of Y-axis.
✓ From this graph, the 85th percentile speed is found out which
gives that speed at or below 85 percent of the vehicles are
passing the point on the highway or only 15% of the vehicles
exceed the spot speed.

91. ✓ The drivers exceeding 85th percentile speed are usually
considered to driver faster than the safe speed under existing
conditions & hence this speed is adopted for the safe speed
limit at this zone. However for the purpose of highway
geometric design the 98th percentile speed is taken.
✓ The 15th percentile speed represents the slower speed limit if it
is desired to prohibit slow moving vehicles to decrease delay &
congestion, as 85% percent of vehicles to the steam travel as
speeds higher than this value & therefore need overtaking
opportunities.
(c) Modal Average : A frequency distribution curve of spot
speeds is plotted with speed of vehicles or average values of each
group of vehicles on the X-axis & the percentage of vehicles in
that group on the Y-axis.
✓ The speed distribution curve is helpful to determine the speed
at which the greatest proportion of vehicles move, given by
modal speed.

92. ✓ All vehicles do not travel at the same speed at a location along
a road. The amount of speed dispersion or the spread from the
average speed affects both capacity & safety.
✓ This may be judged by several methods such as (85th Minus
15th percentile speeds) standard deviation of speeds or the
coefficient of variation in speed.

93. ✓ Example: spot speed studies were carried out at a certain
stretch of highway & the consolidated data collected are given
below.
✓ Determine (i) the upper & lower values or speed limits for
regulation of mixed traffic flow (ii) the design speed for
checking the geometric design elements of highway.
Speed Range
kmph
No.of
vehicles
observed
Speed Range
kmph
No.of
vehicles
observed
0 to 10 12 50 to 60 255
10 to 20 18 60 to 70 119
20 to 30 68 70 to 80 43
30 to 40 89 80 to 90 33
40 to 50 204 90 to 100 9

94. Speed
Range kmph
Mid speed
kmph
Frequency, f
Frequency,
%
Cumulative
Frequency,
%
0 to 10 5 12 1.41 1.41
10 to 20 15 18 2.12 3.53
20 to 30 25 68 8.00 11.53
30 to 40 35 89 10.47 22.00
40 to 50 45 204 24.00 46.00
50 to 60 55 255 33.00 76.00
60 to 70 65 119 14.00 90.00
70 to 80 75 43 5.06 95.06
80 to 90 85 33 3.88 98.94
90 to 100 95 9 1.06 100.00
Total 850 100.00
SOLUTION:

95. ✓ Using the values of mid speed & cumulative frequency%
column 2 & 5 of table, cumulative speed distribution curve us
plotted from this graph the following result are obtained.
✓ (i) Upper speed limits for regulation = 85th percentile speed
= 60kmph
✓ (ii) Lower speed limit for regulation = 15th percentile speed =
30kmph
✓ (iii) Speed to check design elements = 98th percentile speed =
84kmph

96. ✓ SPEED & DELAY STUDY :
✓ The speed & delay studies give the running speed, over all
speeds, fluctuations in speed & the delay between two stations
of a road spaced far apart.
✓ They also give information such as the amount, location
duration frequency & causes of the delay in the traffic stream.
✓ The studies are also utilized in finding the travel time & in
benefit cost analysis.
✓ There are various methods of carrying out speed & delay
study:
✓ Floating car or Riding back method
✓ License plate or vehicle number method
✓ Interview technique method
✓ Elevated observation method
✓ Photographic method

97. ✓ In floating car method a test vehicle is driven over a given
course of travel at approximately the average speed of the stream,
thus trying to float with the traffic stream.
✓ A number of test runs are made along study stretch & group of
observer record the various details.
✓ One observer seated in the floating car with two stop watches.
One of the stop watches is used to record various control points
like intersection, bridges or any other fixed point in each trip.
✓ The other stop watch is used to find the duration of individual
delays.
✓ The average journey time t (minute) for all the vehicles in a traffic
stream in the direction of flow q is given by :
✓ ҧ𝑡 =
𝑡𝑤−𝑛𝑦
𝑞
✓ q=
𝑛𝑎+𝑛𝑦
𝑡𝑎+𝑡𝑤
✓ Where,
✓ q= flow of vehicle, in one direction of the stream

98. ✓ na = average number of vehicle counted in the direction of the stream
when the test vehicle travels in the opposite direction
✓ ny = the average number of vehicle overtaking the test vehicle minus
the number of vehicle overtaken when the test in the direction of q
✓ tw = average journey time, in minute when the test vehicle is
travelling with stream q
✓ ta = average journey time, in minute when test vehicle is running
against the stream q
✓ In the license plate method synchronized stop watches or
voice recording equipment are used. Observer are stationed at
the entrance & exit of a test section where information of
travel time is required.
✓ The timing & vehicle number are noted by the observer of the
selected sample.
✓ But the method does not give such as causes of delays & the
duration & number of delays within the test section

99. ✓ In the interview technique, the work can be completed in a
short time by interviewing & collecting details from the road
users on the spot. However the data collected may not provide
with all the details correctly.
✓ Elevated observation & photographic technique useful for
studying short test section like intersection etc.
✓ Such studies at each intersection will help in evaluating the
efficiency & effectiveness of the control device like signal
system, the remedial measure for accidents etc.

100. ✓ EXAMPLE:
✓ The consolidated are collected from speed & delay studies by
floating car method on a stretch of urban road of length 3.5 km,
running North-South are given below. Determine the average
values of volume, journey speed & running speed of the traffic
stream along either direction.
Trip
No.
Direction of
Trip
Journey Time
Min.Sec
Total
stopped
delay
Min.sec
No.of
vehicle
overtaking
No.of
vehicle
overtaken
No.of
vehicle
from opp.
Direction
1 N – S 6 - 32 1 -40 4 7 268
2 S – N 7 – 14 1 – 50 5 3 186
3 N – S 6 – 50 1 – 30 5 3 280
4 S – N 7 – 40 2 – 00 2 1 200
5 N – S 6 – 10 1 – 10 3 5 250
6 S – N 8 - 00 2 – 22 2 2 170
7 N – S 6 - 28 1 – 40 2 5 290
8 S – N 7 - 30 1 - 40 3 2 160

101. ✓ Solution:
Direction of
Trip
Journey Time
Min.Sec
Total
stopped
delay
Min.sec
Number of vehicles
No.of
vehicle
overtaking
No.of
vehicle
overtaken
No.of
vehicle
from opp.
Direction
N – S 6 - 32 1 -40 4 7 268
6 – 50 1 – 30 5 3 280
6 – 10 1 – 10 3 5 250
6 - 28 1 – 40 2 5 290
Total : 26 – 00 6 – 00 14 20 1088
Mean : 6 – 30 1 – 30 3.5 5.0 272
S – N 7 – 14 1 – 50 5 3 186
7 – 40 2 – 00 2 1 200
8 - 00 2 – 22 2 2 170
7 - 30 1 - 40 3 2 160
Total : 30 – 24 7 – 12 12 8 716
Mean 7 – 36 1 -40 3.0 2.0 179

102. ✓ (i) North – South Direction:
✓ ny = average no.of vehicles overtaking minus overtaken = 3.5 - 5.0
= -1.5
✓ na = average no.of vehicles during trips in opposite direction (from
S –N) = 179
✓ tw = average journey time = 6 min 30 sec = 6.5 min
✓ ta = average journey time during trips against stream = 7 min 36
sec = 7.6 min
✓ q= average volume =
179−1.5
7.6+6.5
= 12.59 veh/min
✓ Average journey time (t) = 6.5 -
(−1.5)
12.59
= 6.62 𝑚𝑖𝑛
✓ Average journey speed =
3.5
6.62
𝑘𝑚/ min
=
3.5 ∗ 60
6.62
= 31.7 𝑘𝑚𝑝ℎ

103. ✓ Average stopped delay = 1.5 min
✓ Average running time = Average journey time – Average stopped
delay
✓ =6.621 – 1.50 = 5.12 min
✓ Average Running speed =
3.5 ∗ 60
5.12
= 41.0 𝑘𝑚𝑝ℎ
✓ (ii) South – North Direction
✓ ny= 3.0 – 2.0 = 1.0
✓ tw= 7.6 min
✓ ta= 6.5 min
✓ na= (from N – S strips) = 272
✓ q=
272+1.0
6.5+ 7.6
= 19.36
𝑣𝑒ℎ
𝑚𝑖𝑛
✓ Journey speed =
3.5∗60
7.55
= 27.8 𝑘𝑚𝑝ℎ
✓ Average stopped delay = 1.8 min

104. ✓ Average running time = 7.55 – 1.8 = 5.75 min
✓ Average running speed =
3.5 ∗60
5.75
= 36.5 𝑘𝑚𝑝ℎ

105. ✓ Trial Cycle Method for Signal :
✓ The 15 Minutes- traffic counts n1 & n2 on road 1 & 2 are noted
during design peak hour flow.
✓ Some suitable trial cycle C1 seconds is assumed & the number of
the assumed cycles in the 15 minutes or 15 * 60 seconds period is
found to be (15 * 60)/C1.
✓ Assuming average time headway 2.5 seconds, the green period G1
& G2 roads 1 & 2 are calculated to clear the traffic during the trial
cycle.
✓ G1 =
2.5n1C1
900
𝑎𝑛𝑑 𝐺2 =
2.5𝑛2𝐶2
900
✓ The amber time periods A1 & A2 are either calculated or assumed
suitably ( 3 to 4 seconds) & the length C1’ is calculated, equal to
(G1 + G2 +A1+A2) seconds.
✓ If the calculated cycle length C1’ works out to be approximately
equal to the assumed cycle length C1, the cycle length is accepted
as the design cycle.
✓ Otherwise the trials are repeated till the cycle length works out
approximately equal to the calculated value.

106. ✓ Example: The 15 minute-traffic counts on road 1 & 2 during peak hour are
observed as 178 & 142 vehicles per lane respectively approaching the
intersection in the direction of heavier traffic flow. If the amber times required
are 3 & 2 seconds respectively for two loads based on approach speeds, design
the signal timing by trail cycle method. Assume an average time headway of
2.5 seconds during green phase.
✓ Solution:
Trail (i)
✓ Assume a trail cycle C1 = 50 Sec
✓ Number of cycle in 15 min = 900/15 = 18
✓ Green time for Road 1, allowing an average time headway of 2.5 sec per
vehicle.
✓ G1 =
178 ∗2.5
18
= 24.7 sec
✓ Green time for Road 2, G2 =
142 ∗2.5
18
= 19.7 𝑠𝑒𝑐
✓ Amber time A1 & A2 are 3 & 2 Sec
✓ Total Cycle length = 24.7 +19.7+3.0+2.0 = 49.4 sec
✓ As this is lower than the assumed trial cycle of 50 sec, another lower cycle
length may be tried.

107. Trail (ii) :
✓ Assume trail cycle C2 = 40 sec
✓ Number of cycle in 15 minutes = 900/40 = 22.5
✓ Green time for Road 1, G1 =
178∗2.5
22.5
= 19.8 𝑠𝑒𝑐
✓ Green time for Road 2, G2 =
142 ∗2.5
22.5
= 15.8 𝑠𝑒𝑐
✓ Total cycle length = 19.8 + 15.8 + 3 + 2 = 40.6 sec
Trial (iii) :
✓ Assume trial cycle C3 = 45 sec
✓ Number of cycle in 15 minutes = 900/45 = 20
✓ Green time for Road 1, G1 =
178 ∗2.5
20
= 22.25 𝑠𝑒𝑐
✓ Green time for Road 2, G2 =
142 ∗2.5
20
= 17.75 𝑠𝑒𝑐
✓ Total cycle length = 22.25+17.75+3+2 = 45.0 sec
✓ Therefore the trail cycle of 45 sec adopted.