The distance along the centre line of a road at which a driver has visibility of an object, stationary or moving at a specified height above the carriageway is called sight distance.
The safe sight distance depends upon the following factors
- Speed of the vehicle.
- Perception time and break reaction time.
- The efficiency of the break of the vehicle.
- The frictional resistance of the road surface.
- The slope of the road surface.
- The eyesight of the driver.
- Weather condition.