Collision Speeds, and How Wrong They Could Be SKID

Before anything else

Every box below is a pair: the lowest the figure could be and the highest. Every answer is a range. A single number here would claim a precision that a tape measure, a drag sled and a human memory do not have, and the width of the band is usually the more useful finding.

Drag factors are not built into this tool, on purpose. A drag factor is a property of that surface, that tyre and that day, and a table in a piece of software is not evidence of any of them — a site test with a drag sled or an instrumented run is what will be asked about. As a starting prompt only, dry asphalt is often somewhere around 0.65 to 0.85, wet asphalt lower, loose gravel lower still and ice far lower, but those are starting points for a measurement, not substitutes for one.

Speed from a slide

Critical speed in a yaw

Could it have stopped

Speed at take-off, from a vault or a fall

Approach speeds from momentum

Directions are degrees anticlockwise from due east, so ninety is north. The departure speeds normally come from a slide calculation, which has a band of its own: carry that band in here rather than entering the middle of it.

The calculation sheet

Every formula, every figure you put in, and every band that came out. This is the thing that goes on the file, because the number on its own is not defensible and the working is.