Why the clock resists a faster drive
Speed rises in a straight line: adding 10 miles per hour always adds 10 to the speedometer. Time does not fall in a straight line. For a fixed distance, travel time is distance divided by speed, so the same speed increase removes a larger share of the trip when you are moving slowly than when you are already moving fast.
That is why accelerating from 30 to 40 mph saves much more time over a given stretch than accelerating from 60 to 70 mph. The second increase is still 10 mph, but it is a much smaller percentage boost. The faster you go, the less time each additional mile per hour can take away.
Why speed feels like a shortcut
Drivers can see speed change immediately; the saved minutes are harder to sense. A 10-mph increase looks like a substantial jump on the dashboard, so it is tempting to expect a similarly substantial cut in arrival time. But the relationship is inverse, not one-for-one: doubling speed halves the time only in the ideal case of covering the same distance continuously at that speed.
Real trips also include time that faster cruising cannot erase, such as waiting at lights or slowing in traffic. Those fixed interruptions make the overall payoff smaller still. The practical implication is simple: a faster stretch may feel dramatically quicker while shifting the arrival time only slightly.
