Overview

This calculator provides minimum-speed estimates using standard formulas from accident investigation references. Results are highly sensitive to drag factor and roadway grade. Use this for training and preliminary analysis, not as a substitute for a licensed reconstruction expert in legal investigations.

Slide To Stop

Skid distance (ft)

Drag factor (mu)

Roadway grade (decimal)

Enter values to calculate speed.

Two Surface Simultaneous Skid

Skid distance (ft)

Left tire drag factor (f1)

Right tire drag factor (f2)

Enter values to calculate speed.

Multi Surface With Optional Impact

Fill one to three surfaces. Leave unused surfaces blank.

Surface 1

Distance (ft) Drag factor Grade

Surface 2

Distance (ft) Drag factor Grade

Surface 3

Distance (ft) Drag factor Grade

Impact

Speed loss due to impact (mph)

Enter at least one surface to calculate.

Conservation Of Momentum (1D Inelastic)

Vehicle 1 mass Vehicle 1 speed (mph, negative allowed)

Vehicle 2 mass Vehicle 2 speed (mph)

Enter both vehicles to calculate post-impact velocity.

Friction Factor Reference

Surface type	Typical drag factor	Notes
Asphalt, new or sharp	0.80-1.20	Very rough, high friction.
Asphalt, traveled	0.60-0.80	Typical roadway wear condition.
Asphalt, polished	0.55-0.75	Smoother surface, lower friction at speed.
Concrete, dry	0.60-0.80	Depends on texture and tire state.
Gravel	0.40-0.60	Loose surfaces reduce consistency.
Grass	0.20-0.55	Strongly affected by moisture.
Snow or ice	0.10-0.25	Very low traction environment.

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For educational use only. Validate assumptions with professional reconstruction workflows.