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Estimated Time of Arrival and Debiasing the Time Saving Bias
Stockholm University, Faculty of Social Sciences, Department of Psychology. Swedish National Road and Transport Research Institute, Linköping, Sweden.
Stockholm University, Faculty of Social Sciences, Department of Psychology. Decision Research, Eugene, USA.
2015 (English)In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 58, no 12, 1939-1946 p.Article in journal (Refereed) Published
Abstract [en]

The time saving bias predicts that the time saved when increasing speed from a high speed is overestimated, and underestimated when increasing speed from a slow speed. In a questionnaire, time saving judgements were investigated when information of estimated time to arrival was provided. In an active driving task, an alternative meter indicating the inverted speed was used to debias judgements. The simulated task was to first drive a distance at a given speed, and then drive the same distance again at the speed the driver judged was required to gain exactly three minutes in travel time compared to the first drive. A control group performed the same task with a speedometer and saved less than the targeted three minutes when increasing speed from a high speed, and more than three minutes when increasing from a low speed. Participants in the alternative meter condition were closer to the target. The two studies corroborate a time saving bias and show that biased intuitive judgements can be debiased by displaying the inverted speed.

Place, publisher, year, edition, pages
2015. Vol. 58, no 12, 1939-1946 p.
Keyword [en]
time saving bias, debiasing, inverted speed, estimated time of arrival, heuristic
National Category
Research subject
URN: urn:nbn:se:su:diva-100757DOI: 10.1080/00140139.2015.1051592ISI: 000367014100002PubMedID: 26230872OAI: diva2:695971
Available from: 2014-02-12 Created: 2014-02-12 Last updated: 2016-01-18Bibliographically approved
In thesis
1. On Physical Relations in Driving: Judgements, Cognition and Perception
Open this publication in new window or tab >>On Physical Relations in Driving: Judgements, Cognition and Perception
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drivers need to make judgements of physical relationships related to driving speed, such as mean speed, risks, travel time and fuel consumption, in order to make optimal choices of vehicle speed. This is also the case for the general public, politicians and other stakeholders who are engaged in traffic issues. This thesis investigates how drivers’ judgements of travel time (Study I and II), fuel consumption (Study III) and mean speed (Study IV) relate to actual physical measures.

A cognitive time-saving bias has been found in judgements of travel time. The time saving bias implies that people overestimate the time saved when increasing speed from a high speed and underestimate the time saved when increasing speed from a low speed. Previous studies have mainly investigated the bias from a cognitive perspective in questionnaires. In Study I the bias was shown to be present when participants were engaged in a driving simulator task where participants primarily rely on perceptual cues. Study II showed that intuitive time saving judgements can be debiased by presenting drivers with an alternative speedometer that indicate the inverted speed in minutes per kilometre.

In Study III, judgements of fuel consumption at increasing and decreasing speeds were examined, and the results showed systematic deviations from correct measures. In particular, professional truck drivers underestimated the fuel saving effect of a decrease in speed. Study IV showed that subjective mean speed judgements differed from objective mean speeds and could predict route choice better than objective mean speeds. The results indicate that biases in these judgements are robust and that they predict behaviour.

The thesis concludes that judgements of mean speeds, time savings and fuel consumption systematically deviate from physical measures. The results have implications for predicting travel behaviour and the design of driver feedback systems.

Abstract [sv]

Förare bör göra bedömningar som relaterar till hastighet, såsom bedömningar av medelhastighet, risk, restid och bränsleåtgång. Dessa bedömningar är nödvändiga för att föraren ska kunna välja en optimal hastighet, men också för att allmänheten, politiker och andra intressenter som är involverade i trafikfrågor ska kunna fatta välgrundade beslut. Denna avhandling består av fyra delstudier där förares bedömningar av restid (Studie I och II), bränsleåtgång (Studie III) och medelhastighet (Studie IV) studeras i relation till faktiska fysikaliska mått.

Tidigare enkätstudier har påvisat ett kognitivt bias i tidsvinstbedömningar vid höga och låga hastigheter som påverkar mänskligt beteende. Studie I visade att detta bias också förekommer i en primärt perceptuell motorisk uppgift där förarna i studien kör i en körsimulator. Studie II visade att dessa intuitiva tidsbedömningar kan förbättras genom att köra med en alternativ hastighetsmätare i bilen som indikerar den inverterade hastigheten i minuter per kilometer istället för hastigheten i kilometer per timme.

I Studie III undersöktes bedömningar av bränsleåtgång vid hastighetsökningar och hastighetssänkningar, och resultaten visar att bedömningarna systematiskt avviker från faktisk bränsleåtgång. Ett intressant resultat var att lastbilsförare i allmänhet underskattade bränslebesparingen som kan göras till följd av en hastighetssänkning. Studie IV visade att subjektiva bedömningar av medelhastighet som avviker från objektiva medelhastigheter kan predicera vägval, vilket tyder på att systematiska fel i dessa bedömningar är robusta och kan predicera vägval.

Sammanfattningsvis visar avhandlingen hur bedömningar av medelhastighet, tidsvinst och bränsleåtgång systematiskt avviker från fysikaliska mått. Resultaten har betydelse för modellering av resebeteende och design av förarstödssystem.

Place, publisher, year, edition, pages
Stockholm: Department of Psychology, Stockholm University, 2014. 52 p.
Time saving bias, fuel consumption, route choice, mean speed, speed choice, time gain, driver judgements
National Category
Research subject
urn:nbn:se:su:diva-100762 (URN)978-91-7447-855-6 (ISBN)
Public defence
2014-03-14, David Magnussonsalen (U31), Frescati Hagväg 8, Stockholm, 10:00 (English)

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted.

Available from: 2014-02-20 Created: 2014-02-12 Last updated: 2014-02-12Bibliographically approved

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