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Inaccuracies in energy efficiency perception based on instantaneous consumption displays – Implications for interface design
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Interactive visual applications create animations that encode changes in the data. For example, cross-filtering dynamically updates linked visualizations based on the user's continuous brushing actions. The animated effects resulting from these interactions depends both on how interaction (e.g., brushing speed) controls properties of the animation such as frame rate, as well as how the data that is being explored dictates the data encoded in the animation. Past work has found that frame rate matters to general perception, however a critical question is which of these animation and data properties affects the perceptual accuracy of judgement tasks, and to what extent. Although graphical perception has been well studied for static data visualizations, it is ripe for exploration in the animated setting. We designed two animated judgment tasks of a target bar in an animated bar chart and empirically evaluate the effects of 2 animations properties - highlighting of the target bar and frame rate - as well as 3 data properties that affect the target bar's value throughout the animation. In short, we find that the rate and timing of animation changes is easier detected in larger values; that encodings such as color are easier to detect than shapes; and that timing is important - earlier changes were harder to perceive as compared to later changes in the animation. Our results are an initial step to understanding perceptual accuracy for animated data visualizations, both for presentations and ultimately as part of interactive applications.
Hybrid electric vehicles (HEVs) have the potential to accomplish high energy efficiency (i.e., low fuel consumption) given that drivers apply effective ecodriving control strategies (i.e., ecodriving behavior). However, HEVs have a relatively complex powertrain and therefore require a considerable knowledge acquisition process to enable optimal ecodriving behavior. The objective of the present research was to examine the acquisition of ecodriving strategy knowledge in HEV drivers who are successful in achieving a relatively high energy efficiency. To this end, we recruited 39 HEV drivers with above-average fuel efficiencies and collected interview data on the ecodriving strategy acquisition process. Drivers reported the acquisition of different types of knowledge as important for ecodriving, namely specific strategy knowledge and general technical system knowledge. They acquired this knowledge both with system-interaction (e.g., actively testing specific strategies, continuous monitoring of energy consumption) and without system-interaction (e.g., internet forums, consulting experts). This learning process took drivers on average 6.4 months or 10062 km. The results show the high diversity of the means that HEV drivers use to develop their ecodriving knowledge and the considerable time it takes HEV drivers to develop their ecodriving strategies.
The number of electric vehicles in service throughout the world has increased from a few thousand in 2009 to some 740,000 in December 2014. These vehicles are often seen as a means of reducing climate and health damaging emissions, and their development is directly supported by some countries and endorsed by the EU. Aside from questions of rebound effects, embedded emissions and cleanness of electricity generation, there are unanswered questions about the energy performance of such cars under a range of driving conditions, and the results of existing studies are not easily interpretable by policymakers and drivers. This study uses the results of extensive dynamometer tests on eight commonly sold electric vehicles. It develops a multivariate model, with regression coefficients around 0.97, to map power demand and energy consumption for all likely combinations of speed and acceleration, producing accessible, easily interpretable displays. While electric vehicles are frequently marketed on the basis of their high acceleration, an important finding is that episodes of modest to high acceleration severely compromise their range and energy efficiency, regardless of speed. This also raises questions as to how well such vehicles perform in the erratic driving conditions of urban traffic.
The actions individuals can take to mitigate climate change are, in the aggregate, significant. Mobilizing individuals to respond personally to climate change, therefore, must be a complementary approach to a nation's climate change strategy. One action item overlooked in the United States has been changing driver behavior or style such that eco-driving becomes the norm rather than the exception. Evidence to date indicates that eco-driving can reduce fuel consumption by 10%, on average and over time, thereby reducing CO2 emissions from driving by an equivalent percentage. A sophisticated, multi-dimensional campaign, going well beyond what has been attempted thus far, will be required to achieve such savings on a large scale, however, involving education (especially involving the use of feedback devices), regulation, fiscal incentives, and social norm reinforcement.
Driving faster or slower? Biased judgments of fuel consumption at changing speeds
- G Eriksson
- O Svenson
Eriksson, G., & Svenson, O. (2012). Driving faster or slower? Biased judgments of fuel consumption at changing speeds. In DIVA (p. 293-297). CRC Press.