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sci.stopping-sight-distance-AASHTO Calculator
Calculates stopping sight distance (SSD) from design speed, reaction time, and braking friction coefficient per AASHTO Green Book: SSD = 0.278Vt + V²/(254f). SSD at 100 km/h with f = 0.35 and t = 2.5 s: SSD = 185 m — vertical and horizontal curves on highways must provide at least SSD.
Inputs
V Kmh
Rate of movement. 1 m/s = 3.6 km/h = 2.237 mph.
F Friction
Ratio of friction to normal force. Rubber on dry concrete: 0.6–0.8. Steel on steel: 0.1–0.15. Ice: ~0.03.
Grade Pct
Reference formula or conversion factor shown for context.
T Reaction S
Duration of the process. Make sure units match the rate inputs (seconds, minutes, or hours).
Results
stopping sight distance SSD (m)
The computed distance or separation.
braking distance (m)
The computed distance or separation.
reaction distance (m)
The computed distance or separation.
SSD = V·t + V²/(2g(f+G))
Reference formula or conversion factor shown for context.
AASHTO design SSD at V
The value at the specified point or condition.
grade effect
Letter or numerical grade indicating quality, creditworthiness, or performance on a defined scale.