Free Web Tool

Sight Distance

AASHTO Stopping Sight Distance with grade and friction adjustment, plus a Passing Sight Distance estimate.

Inputs

Method — AASHTO
  • SSD = 0.278·V·t + V²/(254·(f ± 0.01·G)).
  • PSD ≈ 4.5·V (rural two-lane simplified). AASHTO 2011: PSD by phase formula.
  • f decreases with speed; default 0.32 at 80 km/h.

Results

Reaction distance
Braking distance
SSD
PSD (4.5·V)