Usability Engineering

A: Missed taps cascade into longer glance times, which drives eyes-off-road exposure and failed acceptance tests. Fitts’ Law predicts movement time rises with distance even if targets are bigger; pulling the buttons apart increased amplitude more than it reduced error. Tightening the layout while using physical edges or screen borders keeps error rates down without inflating movement time.

A: Skipping early hazard discovery lets unsafe interaction patterns harden into the architecture, leading to late redesigns or residual risk at launch. The standard exists to surface use errors when you can still change interaction flows, not to pad the test count or paperwork.

A: Relying on sound for a mechanical issue lets unintended engagement damage driveline components before the driver even perceives it. An auditory cue can’t add detent force or block motion; it only informs. Mechanical resistance needs its own control.

A: Underestimating difficulty leads to targets that feel fine in CAD but cause missed inputs and retests. The Shannon formulation uses log2(D/W + 1); mixing bases or flipping the ratio collapses the predicted difficulty and breaks timing estimates.