Explanation of PIEV Time With The Help of a Diagram and The Values of PIEV Time Recommended in Various Countries

The reaction time of the driver is the time taken from the instant the object is visible to the driver and the instant the brakes are effectively applied. The value of the reaction time of the driver depends on several factors. The reaction time can be split up into two parts:

  1. perception time
  2. brake reaction time

The 'perception time' is the time required by the driver to realize that the brakes are to be applied. It is the time from the instant the object comes on the line of sight of the driver to the instant he realizes that the vehicle needs to be stopped.

The 'brake reaction time also depends on several factors including the skill of the driver, the type of the problems, and various other environmental factors.

Generally, the total reaction time of the driver is taken together. The total reaction time may be explained by the ‘PIEV’ theory.

According to 'PIEV' theory, the total reaction time of the driver is split into four parts, That is, time taken by the driver for:

  1. Perception
  2. Intellection
  3. Emotion and
  4. Volition

‘Perception time’ is the time required for the sensations received by the eyes or ears of the driver to be transmitted to the brain through the nervous system and spinal cord. In other words, it is the time required to perceive an object or situation.

‘Intellection time’ is the time required for the driver to understand the situation. It is also the time required for comparing the different thoughts, regrouping, and registering new sensations.

‘Emotion time’ is the time elapsed during emotional sensations and other mental disturbances such as fear, anger, or any other emotional feelings like superstition, etc. with reference to the situation. The emotion time varies for different drivers, but even for a particular driver, the emotion time is likely to vary considerably depending upon the situation or the actual problem involved.

‘Volition time’ is the time taken by the driver for the final action, such as brake application.

The 'PIEV' process has been illustrated in Figure 1.

Figure-1
It is also possible that the driver may apply brakes or take any other avoiding action like turning, by the 'reflex action', without the normal thinking process, which is probably the minimum time for taking a preventive action like brake application. The PIEV time of a driver also depends on several factors such as the physical and psychological characteristics of the driver, type of problem involved. environmental conditions and temporary factors (eg. motive of the trip, travel speed, fatigue, consumption of alcohol, etc.).

The total reaction time of an average driver may vary from 0.5 seconds for simple situations to as much as 3 to 4 seconds or even more in complex problems.

India (IRC)

2.5 Sec

 

Australia

National Association of Australian State Road Authorities (NAASRA)

2.5 sec

Speeds more than 100 km/h

2.0 sec

Speeds less than 100 km/h

1.5 sec

Restricted situations and difficult terrain

Austria

2.0 sec

 

Britain

2.0 sec

 

Canada

Similar to the U.S. policy

 

France

2.0 sec

 

Germany

2.0 sec

For rural roads

1.5 sec

For urban streets

Greece

2.0 sec

For rural roads

1.5 sec

For urban streets

South Africa

2.5 sec

 

Sweden

Swedish national road administration (SNRA)

2.0 sec

Switzerland

2.0 sec

 

United States

2.5 sec

 

(Harwood et al. 1998)


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