Emergency braking from 80 km/h

Inputs & what-if

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Vehicle Braking / Stopping Distance

Vehicle dynamics

The scenario is a straight-line deceleration governed by tyre–road friction and driver reaction time.

Equations

• a = −μ·g·cos(φ) − g·sin(φ)
• d_reaction = v₀·t_r
• d_brake = v₀² / (2|a|)

Validity range

Speeds 5–250 km/h, μ 0.1–1.1, grades ±20%.

Limitations

• Brake fade, tyre temperature, wet-road hydroplaning and suspension dynamics are ignored.
• Real stopping distances vary widely with tyre condition and surface texture.

Sensitivity

Effect of a +10% change on Total stopping distance

Timeline

• 0.00 sHazard perceived — driver reacting
• 1.00 sBrakes applied
• 3.83 sVehicle stopped after 53.81 m

External data & sources

• Dry asphalt friction coefficientreported · medium

  0.7–0.9

  Typical published tyre–road friction ranges (transport research literature) · retrieved 1970-01-01

Assumptions

• Driver reaction time 1.0 s
• Constant friction, no ABS modulation modelled
• Level road
• Constant friction coefficient over the whole stop (ABS-like, no lockup).
• Straight line, no steering input, no load transfer effects.
• Brakes reach full force instantly after reaction time.

Results

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Scientific integrity

Results are computed by an explicit, deterministic model integrated in SI units. Values are labelled as user input, external data, assumption, estimate or calculated result. Simplified models are educational approximations, not engineering-grade predictions.