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On Physical Relations in Driving: Judgements, Cognition and Perception
Stockholm University, Faculty of Social Sciences, Department of Psychology.
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.
Keyword [en]
Time saving bias, fuel consumption, route choice, mean speed, speed choice, time gain, driver judgements
National Category
Psychology
Research subject
Psychology
Identifiers
URN: urn:nbn:se:su:diva-100762ISBN: 978-91-7447-855-6 (print)OAI: oai:DiVA.org:su-100762DiVA: diva2:696015
Public defence
2014-03-14, David Magnussonsalen (U31), Frescati Hagväg 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

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
List of papers
1. The time-saving bias: Judgements, cognition and perception
Open this publication in new window or tab >>The time-saving bias: Judgements, cognition and perception
2013 (English)In: Judgment and decision making, ISSN 1930-2975, E-ISSN 1930-2975, Vol. 8, no 4, 492-497 p.Article in journal (Refereed) Published
Abstract [en]

Biases in people's judgments of time saved by increasing the speed of an activity have been studied mainly with hypothetical scenarios (Svenson, 2008). The present study asked whether the classic time-saving bias persists as a perceptual bias when we control the speed of an activity and assess the perceived time elapsed at different speeds. Specifically, we investigated the time-saving bias in a driving simulator. Each participant was asked to first drive a distance at a given speed and then drive the same distance again at the speed she or he judged necessary to gain exactly three minutes in travel time compared to the first trip. We found that that the time-saving bias applies to active driving and that it affects the choice of driving speed. The drivers' time-saving judgements show that the perception of the time elapsed while driving does not eliminate the time-saving bias.

Keyword
time-saving bias, driving task, time perception, speed choice, time gain, mean speed
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:su:diva-93677 (URN)000322988500008 ()
Note

AuthorCount:3;

Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2017-12-06Bibliographically approved
2. Estimated Time of Arrival and Debiasing the Time Saving Bias
Open this publication in new window or tab >>Estimated Time of Arrival and Debiasing the Time Saving Bias
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.

Keyword
time saving bias, debiasing, inverted speed, estimated time of arrival, heuristic
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:su:diva-100757 (URN)10.1080/00140139.2015.1051592 (DOI)000367014100002 ()26230872 (PubMedID)
Available from: 2014-02-12 Created: 2014-02-12 Last updated: 2017-12-06Bibliographically approved
3. Driving Faster or Slower? Speed Changes and Judged Effects on Fuel Consumption
Open this publication in new window or tab >>Driving Faster or Slower? Speed Changes and Judged Effects on Fuel Consumption
(English)Article in journal (Refereed) Submitted
Abstract [en]

Greenhouse gas emissions from the transport sector continue to increase. Lower speeds on roads would reduce fuel consumption and thereby emissions. Drivers choose the speed of their vehicles, but do they realize the full benefit of a reduced speed on fuel consumption? In a set of questionnaires, professional truck drivers and student groups were asked to judge fuel consumption at decreasing and increasing speeds. The truck drivers underestimated the amount of fuel saved by decreasing speed, but made more accurate judgments of fuel lost at increasing speeds. Student groups made better judgments of fuel saved at decreasing speeds than the truck drivers. It is important that drivers understand the full benefit of a reduced speed on fuel consumption. This may affect both preferred driving speed and attitudes towards lower speed limits. Some policy suggestions on how to promote environmentally efficient driving were discussed.

Keyword
Fuel consumption, speed, truck drivers
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:su:diva-100758 (URN)
External cooperation:
Available from: 2014-02-12 Created: 2014-02-12 Last updated: 2016-08-29Bibliographically approved
4. Judgments of mean speed and predictions of route choice
Open this publication in new window or tab >>Judgments of mean speed and predictions of route choice
2011 (English)In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517, Vol. 14, no 6, 504-511 p.Article in journal (Refereed) Published
Abstract [en]

How are driving speeds integrated when speeds vary along a route? In a first study, we examined heuristic processes used in judgments of mean speed when the mean speeds on parts of the trip varied. The judgments deviated systematically from objective mean speeds because the distances driven at different speeds were given more weight than travel time spent on the different distances. The second study showed that when there was a 10-15 min pause during a travel the effect on the mean speed decrease was underestimated for driving speeds of 90 km/h and higher. In the third study, the objective mean speeds and the subjective biased mean speed judgments were used to predict choices between routes with different speed limits. The results showed that subjective judgments predicted decisions to maximize mean speed significantly better than objective mean speeds. Finally, some applied and basic research implications of the results were discussed.

Keyword
speed, mean speed, judged mean speed, route choice, driving, traffic safety
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:su:diva-70881 (URN)10.1016/j.trf.2011.05.002 (DOI)000297442800008 ()
Note

This research was supported by grants from Bergvalls Stiftelse and the Swedish Research Council and by Grants to Decision Research. The authors want to thank Maria Nyberg and Anna-Lena Erixon for their kind assistance in data collection and analysis. 

Available from: 2012-01-25 Created: 2012-01-24 Last updated: 2017-12-08Bibliographically approved

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