emergency
Braking Distance
Ready
dark_mode
AASHTO Inputs
tune
speed
Speed
straighten
Speed unit
mph
km/h
terrain
Surface friction (f)
Dry asphalt (0.70)
Wet / rain (0.35)
Packed snow (0.20)
Black ice (0.10)
landscape
Road grade (%)
psychology
Reaction time (s)
build
Brake / tyre condition
New pads & tyres
50% wear
Worn / fade risk
calculate
Calculate
restart_alt
Reset
Stopping Distance
analytics
verified
Nominal stop
Within design envelope
—
ft
Total stop
—
m
Total stop
—
Reaction ft
—
Braking ft
—
Total sec
d
brake
= v² / [2 · g · (f + G)]
Total = reaction (v · t) + braking
Stop Path
animation
Blue = reaction · Red = braking
Quick Guide
info
psychology
PRT 2.5 s
is the AASHTO design value for perception-reaction.
terrain
Friction
drops sharply on wet, snow, or ice — distance multiplies.
landscape
Grade
— downhill increases stop distance; uphill shortens it.