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CE 310 : Lecture 3

ROAD USER AND THE VEHICLE

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The success of transportation engineering depends uponthe co-ordination between the two primary elements,namely the vehicles and the road users.

Their characteristics affect the performance of thetransportation system and the transportation engineershould have fairly good understanding about them.

Introduction

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The traffic engineer has to design and operate the trafficfacilities which will be used by pedestrians, cyclist andmotorists.

A knowledge of how this behaviour is influenced by variousexternal conditions will be useful in designing the facility.

Road User

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Diversity (Behaviors)

Driver and other roads have widely varying characteristics.

Traffic controls could be easily designed if all drivers reactedto them in exactly the same way.

The traffic engineer must deal with elderly drivers as well as18-year-olds aggressive drivers and timid drivers. Anddrivers subject to myriad distractions both inside andoutside their vehicles.

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Human behaviour can be studies under the following groups(i) Physiological

(ii) Psychological

Physiological

(i) Vision

Visual acuity,Peripheral vision,

Colour vision,

Glare Recovery,

Depth/Distance Judgment.

(ii) Hearing

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Vision :

Zone of acute vision or visual acuity is formed by acone whose angle is 3 about the centre of the retina- Objects with in this cone - user can read.- 10-12 color & shape can be Identified

This is important when locating traffic signs & signals

Peripheral vision deals with the total visual field forthe 2 eyes with in this field the eyes are able to seeobject, but W\O clear details & color

The angle of Peripheral Vision is about 160 inhorizontal & 115 in vertical

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The angle of peripheral vision falls with speed. It has values of 110degrees at 30 kmph and 40 degrees at 100 kmph. This emphasizesthe need for travel at safe speeds.

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Vision.

Color Vision : It is important for different traffic signal light &traffic signs

Glare Recovery:- The ability of the drivers eyes to adapt to

glare due to head light or variation in lighting conditions is animportant factor. The glare recovery time varies from 3-6 sec.

Depth/Distance Judgment : The ability to judge the depth &dist of an objects & its speed, pedestrian crossing

HearingTo alert the Road user, Defective hearing is not a very seriousproblem.

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Psychological

PIEV Or Perception Reaction Time

(i) Perception(ii) Intellection

(iii) Emotion

(iv)Volition

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PIEV

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Reaction Time

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Space occupied by pedestrians : for design of sub way, foot over bridges

and other facilities, the space required by a pedestrian id generally takenas an ellipse with major axis of 0.6 m and minor axis of 0.45m .

The spacing between pedestrians while walking is generally assumed tobe 2.5 m, which roughly corresponds to a time headway of 2 sec.

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Vehicle Characteristics

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The various vehicle characteristics affecting the road designmay be classified as static and dynamic characteristics.

Static characteristics : Vehicle dimensions, Weight andmaximum turning angle.

Dynamic characteristics : Speed, acceleration and deceleration,

and braking characteristics.

The vehicle speed affects :Sight distanceSuper elevationlength of transition curveWidth of pavementDesign of gradientCapacity of roadDesign and control measures in intersectionThus design speed controls most of the geometric features of

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