This document discusses traffic characteristics and engineering. It defines traffic engineering as dealing with planning and designing streets and highways for safe, efficient traffic flow. Road users and their physical, mental, psychological characteristics are examined, as well as vehicles' static properties like weight and dimensions, and dynamic properties like speed and braking. Traffic surveys study these characteristics to determine road geometry and controls. Perception, intellect, emotion and volition times that make up a driver's total reaction time are also outlined.

1. Chapter-1
TRAFFIC CHARACTERISTICS
Prepared By: Ankit N Patel
Traffic Engineering
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2. What is
TRANSPORTATION
?
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3. Transportation System
Definition of Transportation Modes
 A transportation system is an infrastructure that serves to
move people and goods efficiently.
 Efficient = safe, rapid, comfortable, convenient, economical,
environmentally compatible.
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4. Transportation System
Major transportation subsystems
 Land transportation: highway, rail
 Air transportation: domestic, international
 Water transportation: inland, coastal, ocean
 Pipelines: oil, gas, other
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5. Transportation
Movement of persons and goods over
space
A B
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6. Study of Traffic Engineering
Traffic engineering is a comparatively new branch of engineering and
has grown with the increase in traffic in recent years. As vehicular
traffic began to increase, the congestion on the streets began to
hamper the safe and efficient movement of traffic. More and more
accidents were caused, and serious problems of parking and
environmental pollution began to felt. It was therefore necessary to
give increasing attention to the operational characteristics of highway
transportation and study the need for better geometric design ,
capacity intersections traffic regulations, signals traffic signs,
roadway markings, parking facilities and street lightning.
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7. Introduction to Traffic Engineering
Traffic Engineering
Traffic engineering is that branch of engineering which deals with
planning and geometric design of streets, highway, and
operating traffic systems to achieve safe, economical,
convenient and efficient movement of persons and goods.
Object of Traffic Engineering:
The basic object of traffic engineering is to achieve efficient, free
and rapid flow of traffic with least number of traffic accident.
Factors affecting Traffic:
The Road user
The Vehicle
The Roadway
The environment
Drivers of various types of vehicles and pedestrians are
known as road user. They are human being, hence affected by so
many factors.
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8. Traffic Characteristics
First of the most important scientific study is the study of the
traffic characteristics. Traffic can be classified into two classes:
Road Users.
Vehicular traffic.
Road user characteristics
Human beings performing different roles in the traffic are most
important elements of the traffic and so we have to study their
characteristics and behavior. Various roles of human are such as
driver, pedestrians, cyclists etc. The physical, mental and
emotional characteristics of human beings affect their ability to
operate motor vehicle safely or to service as a pedestrian.
Hence it is important for a traffic engineer to study the
characteristics and limitations of the road users.
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9. Roaduser Characteristics
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10. Traffic Characteristics
The various factors which affect road user characteristics may broadly be
classified under four heads:
Physical
Mental
Psychological
Environmental
Physical characteristics: The permanent physical characteristics of the
driver are vision, hearing, strength and the general reaction to the traffic
situations.
Vision include the acuity of vision, peripheral vision and eye movement;
glare vision, glare recovery and depth judgment. Field of accurate, clear
vision is about a 3 degrees cone however the vision is fairly satisfactory
up to 10 degrees in general and 20 degrees in horizontal plane. In
vertical plane the vision may be limited to 2/3 of that in horizontal plane.
Hearing is helpful for drivers but of more important for the pedestrians
and cyclists.
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11. Traffic Characteristics
Mental Characteristics: Knowledge, skill, intelligence, experience and
literacy can affect the road user characteristics. Knowledge of vehicle
characteristics, traffic behavior, driving practice, rules of roads and
psychology of road users will be quite useful for safe traffic operations.
Psychological factors: These effect reaction to traffic situations of road
users to a great extent. Attentiveness, anger, fear, anxiety, phobias,
superstition, and impatience may effect the traffic performance to great
extent.
Environment factors: The various environmental conditions affecting the
behavior of road user are traffic stream characteristics, facilities to the
traffic, atmospheric conditions and locality. The traffic stream may consist
of mixed traffic or heavy traffic whereas facilities to overtake to the faster
vehicles may be limited. The behavior of the driver varies from one
traffic stream to another.
Similarly the facilities of the traffic separators, multi-lanes etc will effect
the performance. Surrounding environment effect the performance of
the traffic because one will get slower at the market places and will be
faster at the open places.
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12. What is PIEv Theory ?
 Acc. To PIEV theory the total reaction time of the driver is split
into four parts .
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13. 1) Perception time :
 It is the time required for the sensations received by the
eyes or ears to be transmitted to the brain through the
nervous system .
2) Intellection time :
 It is the time required for understanding the situation.
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14. http://www.arrivealive.co.za/images/stoppingdistance.jpg
https://m2.behance.net/rendition/pm/703187/disp/859cc9a079eca4b5556af04b
3aa6215c.png
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15. 3) Emotion time :
 it is time elapsed during emotional sensations & Disturbance
such as fear , anger ,etc. with reference to the situation .
4) Volition time :
 volition time is the time taken for the final action.
 Total reaction time of driver may be vary from 0.5 sec to 4
sec
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Lag distance = v * t
Where, v = speed of vehicle in m/s
t = total reaction time (s) [ as per IRC t = 2.5 s ]
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16. Lag distance
 Definition : The distance travelled by the vehicle during the total
reaction time is known as lag distance .
 Reaction time of the driver is the time taken from the instant the
object is visible to the driver to the instant the brakes are effectively
applied.
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17. Vehicular Characteristics
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18. Traffic Survey
• It is quite important to study the various vehicular
characteristics which affect the design and traffic
performance, because it is possible to design, a road for
any vehicle but not for an indefinite vehicle. It will not
be economically feasible to keep on increasing the
geometric standards and thickness of pavement from
time to time to meet the needs of a few vehicles whose
weight and dimensions are increased.
• Traffic studies are carried out to analyse the traffic
characteristics to decide geometric features and traffic
control for safe and efficient movements.
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19. Traffic Characteristics
A knowledge of these characteristic is necessary for proper
geometric design and traffic control systems allowing for
safe and smooth operations.
– Static: include the weight and size of vehicles.
– Dynamic: involve the forces that cause the motion of vehicle
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20. Traffic Characteristics
Static Characteristics
Design vehicle: the selected representative vehicle for
the geometric design and control systems
– Its dimensions are important for the determination of
design standards for several physical components of the
highway:
– lane width, shoulder width, parking bays length and width,
and lengths of vertical curves.
– Vehicle weight is important for the determination of
pavement depths and maximum grades.
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21. Traffic Characteristics
 Dynamics characteristics of vehicles affecting road design are
speed, acceleration and braking characteristics and some aspects
of vehicle design. The speed and acceleration depends upon the
power of the engine and the resistant to be overcome and are
important in all geometric design elements.
 The deceleration and braking characteristics guide safe vehicle
operation. The stability of vehicle and its safe movement of
horizontal curves are affected by the width of wheel base. The
riding comfort on vertical curves depends on the design of
suspension system of vehicles.
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22. Traffic Characteristics
Power of vehicle
 The power of the heaviest vehicles and their loaded weights
govern the permissible and limiting values of gradient on roads.
From the total hauling capacity and power required to overcome
the total tractive resistance it is possible to determine the speed
and acceleration of the vehicle which in turn useful in traffic
regulation, planning and design.
Braking characteristics
 The deceleration and braking characteristics of vehicles depend
on design and type of breaking system and its efficiency. The
safety of vehicle operation, stopping distance, and the spacing
between two consecutive vehicle in a traffic stream is affected by
the braking capacity. Thus the highway capacity and overtaking
sight distance requirements also get indirectly affected.
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23. THANK
YOU
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