According to the Indian Road Congress(IRC73-1980), in the calculation of Overtaking Sight Distance (OSD), the reaction time 't' of the driver is assumed to be:

Explanation:

As per IRC 73-1980, the reaction time of the driver is assumed to be 2 seconds for the calculation of Overtaking Sight Distance (OSD).

• Reaction time refers to the time taken by the driver to perceive a need to overtake, decide to do so, and then begin the overtaking maneuver. In road design, a 2-second reaction time is typically considered sufficient for a driver to respond to a situation on the road, especially during overtaking.

 Additional Information

• Overtaking Sight Distance (OSD) is the minimum distance required for a driver to safely overtake a vehicle, taking into account the driver's reaction time, the time taken to accelerate, and the distance needed to pass the vehicle.

• It depends on various factors such as the speed of the vehicle, road geometry, and visibility.

• The reaction time of 2 seconds helps ensure that the road provides adequate visibility and time for drivers to safely perform overtaking maneuvers without risking collision with oncoming traffic.