This is the time taken by the driver for detection, identification, decision, and respond.ĭetection: This phase is about being aware of an object when it has entered the driver's field of vision. In the reaction process of a driver, the important characteristic is the perception-reaction time (PRT). Reaction Process - Perception Reaction Time (PRT) In case of green or red color blindness, blue and yellow pigments are added to green and red lights respectively in traffic signals to overcome this difficulty. Important visual deficits like peripheral vision deficits, depth perception deficits, color blindness, cataracts, glaucoma etc also come under visual driver characteristics. Estimation of speed is also performed depending on the field of vision.The driver's attention must be taken for an event happening within the field of vision.The size and dimension of the traffic signs and boards are adjusted to this distance.Traffic signs are placed within 10 degrees range with the expected line of sight of the driver.The field of vision decides some of the traffic engineering practices and functions like: From figure-1, with the increase in speed, the peripheral vision field narrows down as 100 degrees at 20mph and to 40 degrees at 60mph. In visual characteristics, the field of vision explained before is of primary consideration. Other characteristics include hearing, personality, the psychology of the drivers. The two main driver characteristics are visual activity and reaction process. Hence, the behavior of the road user changes with the traffic streams.Īlso Read: Vehicle Traffic Volume Counting Driver Characteristics The traffic stream can be heavy traffic or mixed traffic which may limit the ability to overtake. Environmental FactorsĪtmospheric conditions, traffic facilities, the traffic stream characteristics are the various environmental factors that govern the behavior of the road. These reactions include anger, fear, superstition, impatience, anxiety, etc. Psychological factors affect the reaction of the road user to traffic situations. Proper knowledge of the vehicle characteristics, driving practices, rules of roads and traffic behavior is necessary for safe traffic operations. The important mental characteristics of the road user include skill, intelligence, experience, knowledge and literacy. The lack of strength makes it difficult to park heavy vehicles. This is a less important characteristic compared to others. Hearing characteristics is more important for pedestrians and cycles compared to drivers. It only detects the movement of objects within this field.
A peripheral vision does not show stationary objects. It also extends above and below the line of sight by 60 and 70 degrees respectively. Peripheral Vision: This field of vision extends up to 90 degrees to the right and left of the centerline of the pupil, as shown in figure-1.A vision in this field can identify the color and shape. Fairly clear vision cone: This vision is at 10 to 12 degrees around the line of sight.Acute or clear vision cone: This vision is around 3 to 10 degrees around the line of sight.
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