Sight Distance Calculator

Computes Stopping Sight Distance (SSD), Overtaking Sight Distance (OSD – approx.), and Intersection Sight Distance (ISD) for basic two-lane highways.

Inputs

Current units: SI – speed in km/h, distances in metres.

Design speed Vkm/h

Grade% (positive = upgrade in direction of travel)

Reaction time ts

Friction coefficient ftyp. 0.35–0.4 (dry)

ISD gap times (for vehicle entering intersection)

Results

Enter speed, grade, friction and gap time, then click Compute sight distances.

SSD = reaction distance + braking distance. OSD is approximated from IRC-type design values (level, two-lane, passenger car), interpolated by speed. ISD is based on S = V · t_gap.