Predictability directly trades off against task efficiency
Aliases: predictability cost · human-aware planning · system-level efficiency
What it is
The predictability–efficiency trade-off arises because stable extrapolation may require speed limits, fewer policy switches, or more regular routes, increasing robot time or energy. Robot-local efficiency omits human waiting, surprise, avoidance, and supervision.
Why it happens
A dynamically optimal policy changes whenever new evidence alters immediate cost. For an observer this is non-stationary behaviour that invalidates past learning. Regular motion exchanges local optimality for faster human learning and fewer conflicts. The appropriate unit is total joint-task cost, not trajectory length.
Studying it
Replanning frequency, path regularity, and speed limits can be varied while measuring robot time and energy, human waiting, intervention, conflict, and end-to-end throughput. Repeated use tests strategy learning. Scenario weights should be disclosed rather than presenting a chosen composite score as objectively optimal.
Where it stops holding
Local efficiency can dominate in isolated space or time-critical rescue; coordination dominates in crowds. Predictable chronic delay can induce bypassing and unsafe overtaking. If explicit signalling explains replanning cheaply, routes need not carry all predictability.
Applying it
- Include human waiting, detours, false stops, and supervision in optimisation and acceptance criteria.
- Adapt policy to traffic and risk while making switches visible and limiting switch frequency.
- Compare local motion cost against throughput and conflict on a Pareto frontier, selecting an explicit compromise and monitoring drift.
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 · X2.05.3 Unavoidable discontinuities require a perceptible warning
- Adjacent: X2.02 Motion legibility · X4.03 Supervisory control
- Search terms:
predictability efficiency trade-off·human-aware planning·system-level cost