Braking Mark
Definition
A continuous black skid produced when wheels are fully locked under braking and the tyre slides on the road. Length plus drag factor gives a minimum speed at the start of the skid.
- Appearance
- Continuous black skid mark
- Cause
- Wheels fully locked, tyre sliding on road surface
- Use
- Calculated with drag factor to estimate minimum speed
- Field
- Accident and hit-and-run investigation
Common questions
How does a braking mark differ from a yaw mark at a collision scene?+
A braking mark is a continuous straight or near-straight skid from wheels locked under braking, while a yaw mark is a curved scuff produced when a vehicle slides sideways while still rotating, and the two are read differently when reconstructing pre-impact vehicle behaviour.
Why does a braking mark only give a minimum speed, not the actual speed?+
The calculation using mark length and drag factor gives the speed at the start of the visible skid, but any earlier braking before the mark started, or speed lost after the mark ends, is not captured, so the result is a floor on speed rather than an exact figure.
Related terms
- Drag Factor (μ)
- The effective coefficient of friction between the tyre and the road surface during a braking event. Used in the skid-mark speed formula....
- EDR (Event Data Recorder)
- An onboard module that records pre-crash speed, throttle, brake application, steering input and seatbelt status for several seconds before airbag deployment. The...
- Gouge Mark
- A scrape or trench cut into the pavement when a metal component (frame, axle, undercarriage) strikes the road during or after impact....
- Paint Transfer
- Layers of paint left on a struck vehicle, pedestrian's clothing, or roadside object during contact. The layer sequence, ordered from primer outward,...
- Yaw Mark
- A curved, striated tyre impression produced when a vehicle slides at an angle to its direction of travel during a steered or...