CHARACTERISTICS OF TRAFFIC ENGINEERNG

TRAFFIC ENGINEERING Deals with improvement of traffic performance of Road Networks. Application of Scientific principles and Techniques for safe ,rapid, convenient &economic movement of people. .

TRAFFIC characteristics Road User Characteristics Vehicular Characteristics

Road user characteristics Considers the aspects of human behavior on roads. PHYSIOLOGICAL CHARACTERISTICS- Measurable and Usually Quantifiable Characteristics Vision Hearing PSYCHOLOGICAL CHARACTERISTCS- More difficult to measure and quantify Perception Intellection Emotion Volition

vision 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.

(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

glare recovery Driver’s Ability to adapt glare and variations in lighting conditions. Factors affecting Glare recovery –Age, Wearing of eyeglasses Recovery time : 3-6 seconds

colour vision Most important for identifying : - Traffic lights -Traffic signs Drivers feel difficulty to recognize proper signals.

depth perception 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.

hearing Very vital to road user. To hear SOUND OF HORNS Alert Pedestrians Important to elderly people with falling eyesight

psychological characteristics PIEV THEORY PERCEPTION INTELLECTION EMOTION VOLITION

psychological characteristics 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

Age of driver 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 Take time to absorb traffic control information 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

Vehicular characteristics

Vehicular characteristics Affect the design and Traffic performance. Vehicular characteristics consist of Static Characteristics Dynamic Characteristics Static Characteristics include dimensions, weight and maximum turning angle. Dynamic Characteristics include Speed, Acceleration , braking Characteristics and some aspects of body design.

static characteristics 1.VEHICLE DIMENSIONS a). 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 (contd..) 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.

static characteristics (contd..) 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.

Dynamic characteristics a). SPEED: it affects Sight distances Superelevation Length of transition curve Vertical curves Width of pavement and shoulders Design gradient Capacity of traffic lane Design of intersections. Design speed controls most of the geometric features of the highway.

Dynamic characteristics (contd..) b) ACCELERATION: Governed by Vehicle transmission system, weight and horse power. Maximum deceleration rate depends upon friction between tyres and pavement.

Dynamic characteristics (contd..) 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.

Vehicle lighting system 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.