Sight Distance 1
Sight Distance 1 : The distance, measured along the road over which visibility occurs between a driver and an object or between two drivers at specific heights above the carriageway in their lane of travel. (1) Approach sight distance (ASD) The distance required for a driver to perceive marking or hazards on the road surface approaching an intersection and to stop. (2) Car stopping distance (CSD) The distance required for a car driver to perceive a hazard, react and brake to a stop. For design purposes, wet weather conditions and locked wheel braking are assumed. (3) Entering sight distance (ESD) The sight distance required for minor road drivers to enter a major road via a left or right turn, such that traffic on the road is unimpeded. (4) Manoeuvre sight distance (MSD) The distance required for an alert car driver to perceive an object on the road and to take evasive action. (5) Minimum gap sight distance (MGSD) The minimum sight distance based on the gap necessary to perform a particular movement. (6) Overtaking sight distance (OSD) The sight distance required for a driver to initiate and safely complete an overtaking manoeuvre. (7) Railway crossing sight triangle The clear area required for a truck driver to perceive a train approaching an uncontrolled railway crossing and to stop the truck. (8) Safe intersection sight distance (SISD) The distance required for a driver in a major road to observe a vehicle entering from a side road, and to stop before colliding with it. (9) Sight distance through underpass The distance required for a truck driver to see beneath a bridge located across the main road, to perceive any hazard on the road ahead, and to stop. (10) Stopping sight distance The sight distance required by an average driver (car or truck depending on design requirements), travelling at a given speed, to react and stop before striking an object on the road. (11) Truck Stopping sight distance Distance required for a truck driver to perceive a hazard, react and brake to a stop. For design purposes, the braking of an unladen vehicle in wet weather conditions without locking the wheels is assumed
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