Sight Distance Calc

Stopping & passing & decision sight distance, lateral clearance on a horizontal curve, and the minimum length of crest and sag vertical curves — every formula shown with its AASHTO/DPWH criterion, ready to print.

⭐ Solve … EP per calculation · Balance … EP

Driver & sight-line parameters (shared)

AASHTO default heights are pre-filled. Used by SSD, the crest curve (eye + object), and the sag curve (headlight + beam angle).

Perception–reaction time t (s)

Deceleration a (m/s²)

Driver eye height h₁ (m)

Object height h₂ (m)

Headlight height H (m)

Headlight beam upward angle β (°)

Stopping Sight Distance (SSD)

Design speed V (kph)

Grade g (%)

PSD (passing) and DSD (decision) are read from AASHTO design tables shown with the result.

Sight distance on a horizontal curve

Centreline radius R (m)

Sight distance S (m)

Minimum crest vertical-curve length

Incoming grade g₁ (%)

Outgoing grade g₂ (%)

Required sight distance S (m)

Uses the eye height h₁ and object height h₂ from the shared parameters above (AASHTO crest criterion).

Minimum sag vertical-curve length