Elements of Access: Time is Mis-underestimated (Vierordt’s Law)

Reported trip durations by minute for work trips (2011 Twin Cities Travel Behavior Inventory) shows spiking on
Reported trip durations by minute for work trips (2011 Twin Cities Travel Behavior Inventory) shows spiking on “5s” and “10s” and “30s” (Log Scale)

Sometimes people think places are farther away than they really are, and other times they are closer. Freeways seem to take shorter than they really area, local streets longer. This in part has to do with task complexity, or the “mental transaction costs” involved in traveling.⁠1

When I need to make a lot of small driving and navigation decisions, like on a signalized route with lots of turns, I need to focus on driving more times. Each time I am engaging my conscious brain in traveling decisions. More brain-space is occupied by traveling thoughts.

Other factors include temporal relevance (is the trip important), temporal expectancies (what do I think the travel time will be) temporal uncertainty (how reliable is my estimate of travel time), affective elements (what is the emotional state of the traveler), absorption and attentional deployment (am I paying attention to the task at hand) and arousal (how physically activated am I, am I on drugs?).⁠2

When I can drive on an uncongested freeway, I can avoid many such thoughts. Driving is less salient. Time passes faster. As the expression goes, “time flies when you are having fun”

In travel surveys we have a common phenomenon of rounding reported times, and times are usually rounded up. So if a trip was 14 minutes, it would be rounded to 15 minutes. If it were 22 minutes, it might be rounded to 25 or even 30 minutes. This makes self-reported times significantly biased in travel analysis. Until recently, that was the only data available. But now with the advent of GPS devices and cheap sensors tracking traffic across networks, we can get much better speed and travel time estimates.

Vierordt’s Law claims people are more likely to over-estimate short times and under-estimate long times.

We did not corroborate this with a driving simulator study for waiting at a traffic signal.⁠3 Perceived and actual waiting time were virtually identical for the first 30 seconds, but for times greater than 30 seconds, actual waiting time was higher than perceived waiting time, up to 120 seconds. At 120 seconds, the trend was for perceived time to overtake actual time, but that was the cut-off for the experiment, so perception findings in this situation require more information. However, the annoyance level at 120 seconds of waiting was much higher than the annoyance of waiting 30 seconds. Further people hated stops.

Of course, with all of this, it depends on how you frame the question, what you ask, and what travelers were expecting. Comparing a computer-administered stated preference with one in which travelers were in a driving simulator completely flipped preferences for traveling (waiting for free flowing travel vs. muddling through in congestion).⁠4

1 Parthasarathi, Pavithra, David Levinson, and Hartwig Hochmair (2013) “Network Structure and Travel Time Perception.” PLOS ONE: 8(10): e77718.

2 Carrion, C. and D. Levinson (2012). Uncovering the influence of commuters’ perception on the reliability ratio. Technical report.

3 Wu, X., D. M. Levinson, and H. X. Liu (2009). Perception of waiting time at signalized intersections. Transportation Research Record: Journal of the Transportation Research Board 2135(1), 52–59.

4 Levinson, D., K. Harder, J. Bloomfield, and K. Carlson (2006). Waiting tolerance: Ramp delay vs. freeway congestion. Transportation Research Part F: Traffic Psychology and Behaviour. 9 (1), 1–13.