Vehicle Braking Distance
Stopping distance from speed, friction, grade, reaction time.
Example
You enter
- Speed (mph) 55
- Road friction coefficient 0.7
- Reaction time (s) 1.5
You get
- Braking distance 144.1 ft
- Reaction distance 121.0 ft
- Total stopping distance 265.1 ft
- Effective friction 0.7
Details, formula, and sources
Braking distance d = v² / (2 × g × (μ + grade)) + reaction_distance. Reaction distance = v × t_reaction. g = 32.2 ft/s².
Classical kinematics; AASHTO 'Policy on Geometric Design of Highways and Streets' (Green Book) by name.
AASHTO Green Book licensed; kinematics free in physics texts.
Estimate. AHJ and licensed fire protection engineer govern.
Field names used by the API: speed_mph, friction_coefficient, reaction_time_s, braking_distance_ft, reaction_distance_ft, total_distance_ft, effective_friction
- Default friction μ 0.7 dry asphalt / 0.4 wet / 0.2 ice unless user suppliesAASHTO Green Book typical
- Default reaction time 1.5 s unless user suppliesAASHTO Green Book typical