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CHARACTERISTICS OF TRAFFIC ENGINEERNG

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Deals with improvement of traffic performance of Road

Networks.

Application of Scientific principles and Techniques for

safe ,rapid, convenient &economic movement of

people.

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TRAFFIC ENGINEERING

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Road User Characteristics

Vehicular Characteristics

TRAFFIC CHARACTERISTICS

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Considers the aspects of human behavior on roads.

PHYSIOLOGICAL CHARACTERISTICS- Measurable and Usually Quantifiable Characteristics

VisionHearing

PSYCHOLOGICAL CHARACTERISTCS- More difficult to measure and quantify

PerceptionIntellectionEmotionVolition

ROAD USER CHARACTERISTICS

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Most important factor that affects highway

design & safety.

(a). Acute or clear vision cone-Field of clearest

& acute vision is within the cone whose angle is

3° about the centre line of Retina.

Helps for Distant Vision.

VISION

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(b)Fairly clear vision cone- Vision is satisfactory

when angle of cone is 10° to 12° around the line of

sight;

color and shape can be identified in this field.

Important for locating Traffic signs and signals.

(c) Peripheral Vision- Total Visual Field for two eyes.

Vision is possible but without clear details and colour.

Angle of Peripheral Vision-

160 ° in horizontal Direction

115 ° in vertical Direction.

VISION

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Driver’s Ability to adapt glare and variations in lighting conditions.

Factors affecting Glare recovery –Age, Wearing of eyeglasses

Recovery time : 3-6 seconds

GLARE RECOVERY

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Most important for

identifying :

- Traffic lights

-Traffic signs

Drivers feel difficulty to

recognize proper signals.

COLOUR VISION

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Ability to judge the distance and speed of approaching vehicles

Important to pedestrians to cross the road.

For Driver ,judgment of speed of other vehicles is important.

DEPTH PERCEPTION

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Very vital to road user.

To hear SOUND OF HORNS

Alert Pedestrians

Important to elderly people with falling

eyesight

HEARING

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PIEV THEORY

PERCEPTION

INTELLECTION

EMOTION

VOLITION

PSYCHOLOGICAL CHARACTERISTICS

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PERCEPTION: Time required to perceive an

object

INTELLECTION: Time required for

understanding the situation.

EMOTION: Time elapsed during emotional

sensations and disturbances.

VOLITION: Time taken for final action

PSYCHOLOGICAL CHARACTERISTICS

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Problems of younger drivers

Difficulty in judging speed, distance and reaction time

Tend to concentrate on near objects

Missing the important information, because its

relevance is not understood

Having difficulty in integrating information

Under-estimating the risk of accident involvement

Making less effective driving decisions

AGE OF DRIVER

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Problems of older drivers

Difficulties in rapid decision making

At intersections

Take time to absorb traffic control information

Difficulty at night

Lower light level

Headlight glare

Readily fatigued

AGE OF DRIVER

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VEHICULAR CHARACTERISTICS

Affect the design and Traffic performance.

Vehicular characteristics consist of Static CharacteristicsDynamic Characteristics

Static Characteristics include dimensions, weight and

maximum turning angle.

Dynamic Characteristics include Speed, Acceleration ,

braking Characteristics and some aspects of body design.

VEHICULAR CHARACTERISTICS

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1.VEHICLE DIMENSIONSa). Width : Affect width of traffic lanes, shoulders

& parking facilities .

b). Height: Affects the clearance of overhead structures. Clearance under over bridges, under bridges,

electric & other service lines.

Height of driver seat –provide clear vision of the road to his front & sides.

Height of headlight- affects sight distances at valley curves.

STATIC CHARACTERISTICS

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c). Length: Important factor in design of Horizontal

alignment

Length affects

safe overtaking distance

Capacity of road

Extrawidening

minimum turning radius

Parking Facilities

Design of valley curves.

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STATIC CHARACTERISTICS(contd..)

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2). WEIGHT: Affects design of pavement

thickness & gradients.

Limiting gradients are governed by weight

& power of vehicles.

STATIC CHARACTERISTICS(contd..)

3) . POWER: Power of heaviest and loaded weights

vehicle govern permissible and limiting gradients.

Power affects the speed and acceleration of vehicle.

4). MINIMUM TURNING RADIUS : Depends on

length of wheel base and features of steering

system

Affects design of sharp curves. 22

STATIC CHARACTERISTICS(contd..)

a). SPEED: it affectsSight distancesSuperelevationLength of transition curveVertical curvesWidth of pavement and shouldersDesign gradientCapacity of traffic laneDesign of intersections.

Design speed controls most of the geometric features of the highway.

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DYNAMIC CHARACTERISTICS

b) ACCELERATION: Governed by Vehicle

transmission system, weight and horse power.

Maximum deceleration rate depends upon

friction between tyres and pavement.

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DYNAMIC CHARACTERISTICS(contd..)

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BRAKING CHARACTERISTICS: Important for

safety.

Affects Safety of vehicle operation ,stopping

distance and the spacing between two

consecutive vehicles in a traffic steam

Interaction between tyre & road surface governs

braking performance.

One of the prime causes of accidents during

braking is the wheels getting locked and driver

losing control of the vehicle.

DYNAMIC CHARACTERISTICS(contd..)

Lighting system consist of

a). Headlight

To provide a main beam for the driver to see the road ahead.

To provide a dipper beam for avoiding glare to the opposing

traffic.

b). Rear Lamps : Give indication to the driver about presence

of a vehicle infront of him Avoid Front- to rear collision.

c). Direction Indicators : Give adequate notice of the

intention of driver to turn or to stop.

Usually amber in colour. 26

VEHICLE LIGHTING SYSTEM

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