Highway Design Speed Calculator

Design Parameters

Design Speed (mph)

Road Type

Grade (%)

Lane Width (ft)

Driver Eye Height (ft)

Object Height (ft)

Superelevation Rate (%)

Side Friction Factor

Stopping Sight Distance

887 ft

Perception-Reaction Distance: 221 ft + Braking Distance: 667 ft

Perception-Reaction

221 ft

Braking Distance

667 ft

Total SSD

887 ft

Component	Value	Formula
Perception-Reaction Distance	221 ft	1.47 × V × t
Braking Distance	667 ft	V² / (30 × (f ± G))
Stopping Sight Distance	887 ft	PRD + BD