TRAFFIC ENGINEERING
TRAFFIC ENGINEERING
Traffic engineering is that branch of engineering which deals with the improvement of
traffic performance on road network and terminals through systematic traffic studies,
scientific analysis and engineering applications which provide safe, rapid, efficient
convenient and economic transportation of persons and goods.
• Traffic engineering includes planning and geometric design on one hand and
regulation and control on the other.
• The road traffic is composed of different categories of vehicular traffic and pedestrian
traffic. Each category of vehicular traffic has two components, the human element as
the driver and the machine as the vehicle.
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Scope of traffic engineering
• The basic objective of traffic engineering is to achieve efficient, free and rapid flow of
traffic, with least number of traffic accidents.
The study of traffic engineering may be divided into seven major areas:
i. Traffic characteristics
ii. Traffic studies and analysis
iii. Planning and analysis
iv. Geometric design
v. Traffic operation, regulation and control
vi. Road safety aspects
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vii.Administration and management

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Scope of traffic engineering (contd….)
• The traffic characteristics are quite complex with various types of road users on the
roads moving with different motives.
• The human psychology and vehicular characteristics are to be give due importance.
• The various studies to be carried out on the actual traffic include speed, volume,
capacity, travel patterns, origin and destination, traffic flow characteristics, parking
and accident studies.
• Traffic planning is a separate phase for major highways like expressways, arterial
roads, mass transit facilities and parking facilities.
• All geometric design aspects such as cross section and road surface details, sight
distance requirement, horizontal and vertical alignment, manoeuvre areas,
intersections and parking facilities are to be suitably designed for better performance.
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TRAFFIC ENGINEERING
Scope of traffic engineering (contd….)
• Traffic operation deal with regulations, control and the warrants, whereas regulations
are in the form of laws and ordinances etc.
• Installation of traffic control devices like signs, signals, islands and pavement markings
are most common means to regulate ad control the traffic.
• Actual adoption of traffic management measures, such as traffic regulations and
control need adequate attention.
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Traffic characteristics
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Traffic
characteristics
Road user
characteristics
Vehicular
characteristics

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i. Road user characteristics
The human element is involved in all actions of the road users either as pedestrian,
cyclist, motorist.
The various factors which affect human characteristics as road users are:
a) Physical
b) Mental
c) Psychological and
d) Environmental
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i. Road user characteristics (contd….)
Physical characteristics
• The physical characteristics of road users are either permanent or temporary
• The permanent characteristics are the vision, hearing, strength and the general
reaction to traffic situations.
• Vision plays most important role of all these, which include acuity/sharpness of
vision, peripheral vision, eye movement and depth judgement.
• Glare vision and glare recovery time of drivers play important role during night.
• Minimum standards for acuity of vision are often laid down by licensing authority.
• In vertical planes, the field of clear vision may be about two thirds of that in the
horizontal plane.
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TRAFFIC ENGINEERING
i. Road user characteristics
Physical characteristics (contd…)
• These factors are particularly taken care of while designing and installing traffic
control devices.
• As the field of clear vision limited, the road users have to often shift their eyes within
the peripheral field to obtain clear vision. The total time taken for the eye movement
depends on some of the physical characteristics including the response to stimuli.
• The depth judgement is important for a driver in judging distance and speed of
vehicles and other objects ahead.
• The effect of glare and adoptability to change of light should also be studied.
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i. Road user characteristics
Physical characteristics (contd…)
• The reaction to traffic situations depends on the time required to perceive and
understand the traffic situation and to take the appropriate action.
• Also, the time required to take an appropriate action depends on the type of the
problem and the familiarity with similar situations.
• The temporary characteristics of road users affecting their efficiency are fatigue,
alcohol or drugs and illness, which reduce alertness and increase the reaction time
and also do affect the quality of judgement in some situations.
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i. Road user characteristics
Mental factors
• These include knowledge, skill, intelligence, experience and literacy which affect the
road user characteristics.
• Knowledge of vehicle characteristics, traffic behaviour, diving practice, rules of roads
and psychology of road users will be quite useful for safe traffic operations.
• Understanding the traffic regulation and special instruction to road users and timely
action depends on intelligence and literacy.
• Reaction to certain traffic situations become more spontaneous with experience.
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i. Road user characteristics
Psychological factors
• The emotional factors such as attentiveness, fear, anger, superstition, impatience,
general attitude toward traffic and regulations and maturity also come under this
category
• These affect reaction to traffic situations of road users to a great extent.
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i. Road user characteristics
Environmental factors
• The various environmental factors/conditions affecting the behaviour of road user are
traffic stream characteristics, roadside features, atmospheric conditions and the
locality.
• The traffic stream may consist of mixed traffic or heavy traffic.
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ii. Vehicular characteristics
• It is important to study the various vehicular characteristics which affect the design of
the road facilities and the traffic performance.
• It will not be economically feasible to keep on increasing the geometric standards
and thickness of pavements from time to time to meet the needs of a few vehicles
whose dimensions and weights are increased.
• Hence standards for the dimensions and weights of vehicles should be consistent
within a country with the road facilities now available or could be made available in
the near feature.
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ii. Vehicular characteristics (contd…)
The various vehicular characteristics affecting the road design are classified as,
i. Static characteristics and
ii. Dynamic characteristics of the vehicles.
• Static characteristics include relevant dimensions, maximum turning angle and the
total weight.
• Dynamic characteristics include speed, acceleration/deceleration, braking
characteristics and vehicle body design.
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