Time-Saving Bias
🇳🇴TidsbesparelsesbiasDefinition
The time-saving bias, identified by Ola Svenson (2008), is a systematic error in how people estimate the time saved by increasing speed. Because the relationship between speed and travel time is hyperbolic (not linear), people dramatically overestimate time savings when accelerating at high speeds and underestimate savings when accelerating at low speeds. Intuitively, increasing speed from 30 to 40 km/h feels like a modest improvement, while increasing from 100 to 110 km/h feels significant—but mathematically, the former saves far more time per kilometer. This bias reflects a broader difficulty humans have with non-linear functions, similar to the challenges we face with compound interest, exponential growth, and probability.
Real-world example
A driver traveling 10 km at 100 km/h takes 6 minutes. Increasing speed to 110 km/h saves only 33 seconds. But the same driver traveling at 30 km/h takes 20 minutes, and increasing to 40 km/h saves 5 full minutes—nine times the saving. Despite this, commuters and transport planners consistently prioritize highway speed increases over urban speed improvements. In aviation, airlines market flight time reductions of minutes on already-fast routes while passengers undervalue the much larger time savings from reducing ground transport delays. The bias also affects workplace productivity: managers invest in tools that shave seconds off fast processes while ignoring bottlenecks in slow processes where far greater gains are available.
Supplementary perspective
The time-saving bias connects to the planning fallacy (poor estimation of durations) and optimism bias (believing we can compress time). It also reflects a general human weakness with non-linear mathematics that appears in other domains—such as underestimating the impact of small interest rate changes on long-term debt, or misjudging the acceleration of pandemic curves. Transportation engineers and UX designers can use this insight to communicate time savings more honestly.
Practical advice
Recognize
- —When evaluating speed improvements, convert to actual minutes saved rather than relying on the intuitive feeling that 'faster is always significantly better.'
- —Be suspicious of percentage-based speed claims—a 10 % speed increase yields vastly different absolute time savings depending on the baseline speed.
Counteract
- —Always calculate time savings in absolute terms (minutes, hours) using the formula: time = distance ÷ speed, and compare the 'before' and 'after' values explicitly.
- —When prioritizing efficiency improvements, rank interventions by absolute time saved, not by speed increase—this almost always redirects attention to slow processes with large improvement potential.
Ethical use
- —In transportation, logistics, and productivity tools, present time savings in absolute units (minutes saved per trip) rather than speed increases (km/h gained), which are inherently misleading.
- —Avoid marketing claims that exploit the bias—advertising '20 % faster!' when the actual saving is negligible undermines informed decision-making.