Time-saving bias
We badly misjudge how much time a change in speed actually saves.
What it means
A systematic error in estimating the time gained or lost by altering speed: people overestimate the savings from raising an already-high speed and underestimate the much larger savings available from speeding up a low one. The error arises because intuition treats time saved as roughly proportional to the increase in speed, when in fact it depends on the change in the reciprocal of speed, so the relationship is sharply nonlinear. The consequence is misallocated effort and risk — drivers floor it to shave trivial minutes off a fast trip while shrugging at slow stretches where the same effort would help far more. The bias generalizes to any productivity or throughput judgment framed as a rate, and it matters for road safety, scheduling, and any decision that trades risk for a misperceived gain in time.
Examples
Asked which saves more time, raising speed from 25 to 40 mph or from 70 to 85 mph, most people pick the wrong one — the slow-road increase saves far more time over the same distance.
A team pours effort into speeding up an already-fast build from 30 seconds to 20, while the ten-minute test suite, where the same effort would repay many times over, is left alone.
Households pay to upgrade from 500 Mbps to a gigabit and shave a fraction of a second off a download; the same doubling applied to a 5 Mbps line would save minutes.
First described in Eyal Peer (2010); building on Svenson.