Time-Saving Bias
People's tendency to misestimate the time that could be saved (or lost) when increasing (or decreasing) speed. In general, people underestimate the time that could be saved when increasing from a relatively low speed (e.g., 25 mph or 40 km/h) and overestimate the time that could be saved when increasing from a relatively high speed (e.g., 55 mph or 90 km/h).
Origin
Swedish psychologist Ola Svenson at Stockholm University first published research on the phenomenon in 1970 in the Journal of Experimental Psychology, showing that people systematically misjudge the time implications of speed changes. The bias arises because the relationship between speed and travel time is hyperbolic — not linear — and people apply a flawed "proportion heuristic" instead. Svenson continued refining the research through studies in 1971, 1973, and a major 2008 paper in Acta Psychologica.
Everyday Use
Going from 30 to 40 mph saves far more time on a trip than going from 70 to 80 mph, but it doesn't feel that way. We intuitively think the same speed increase yields the same time savings, but the relationship between speed and time is curved, not straight. This is why lowering speed limits in cities has a bigger safety payoff than people expect, and why speeding on the highway saves less time than it feels like.