Unavoidable discontinuities require a perceptible warning
Aliases: pre-motion warning · change alert · directional warning
What it is
A discontinuity pre-alert communicates the type and direction of an unavoidable sharp turn, stop, or acceleration before it occurs. It does not justify poor motion; it restores minimum prediction and response time when dynamics or emergency goals prevent continuity.
Why it happens
The alert turns an event that cannot be extrapolated into a conditional expectation. People orient, update occupancy, and prepare avoidance. A generic beep captures attention without indicating where to move, while a cue after turning begins only explains. Poor reliability leads to disregard or unnecessary response.
Studying it
No cue, generic cue, and directional cue can be compared across lead time and reliability using orientation onset, correct avoidance side, conflict, startle, and false waiting. Hazardous cases should progress from simulation to speed-limited trials. Measured cue-to-motion intervals matter more than configured values.
Where it stops holding
An instantaneous disturbance may leave no warning time; protective control then dominates, followed by explanation. Repeated replans should be reduced rather than alarmed individually. No sensory channel reaches every person or condition, so safety meaning needs redundancy.
Applying it
- Distinguish emergency stop, turn, and acceleration with directional patterns and preserve feasible lead time.
- Retract cancelled warnings immediately; default to conservative motion when the signalling chain fails.
- During realistic primary work and noise, measure correct avoidance, misses, false alarms, and actual lead time rather than playback success.
Related
- Same group: X2.05.1 Constant and gradual motion is easier to predict than sudden acceleration · X2.05.2 Direction or speed discontinuities are perceived as loss of control or failure · X2.05.4 Predictability directly trades off against task efficiency
- Adjacent: X2.01 Previewing action intent · X5.03 Emergency stop
- Search terms:
pre-motion warning·directional alert·warning lead time