Corner sight distance
Corner sight distance (CSD) is the road alignment specification which provides a substantially clear line of sight so that the driver of a vehicle, bicyclist or pedestrian waiting at the crossroad may safely anticipate the driver of an approaching vehicle. Corner sight provides an adequate time for the waiting user to either cross all lanes of through traffic, cross the near lanes and turn left, or turn right, without requiring through traffic to radically alter their speed.
When determining corner sight distance, a set back distance for the vehicle waiting at the crossroad must be assumed. Set back for the driver of the vehicle on the crossroad has been standardized by some state MUTCDs and design manuals to be up to a minimum of 10 feet plus the shoulder width of the major road but not less than 15 feet. However, the Federal MUTCD requires that a stop line, if used, shall be at least 4 feet from the nearest travel lane. Line of sight for corner sight distance is to be determined from a 3 and 1/2-foot eye height at the vehicle driver’s location on the minor road to a 4 and 1/4-foot object height in the center of the approaching lane of the major road. Corner sight distance, D, is equivalent to a specified time gap, at the design speed, required for a stopped vehicle to turn right or left.
For passenger vehicles at two lane intersections, this time gap equivalence is commonly a distance 7.5 seconds away at the design speed. Longer gaps are required for trucks and buses, and for multilane roads.Generally, the public right-of-way should include and maintain this line-of-sight.Related formulas
|vorner sight distance (m)
|design speed (m/s)
|specified time gap (s)