Eco-driving performance assessment with in-car visual and haptic feedback assistance

In this experiment, 28 participants completed an urban driving task in the CARDS simulator at Renault’s Technical Centre for Simulation. This simulator, based on the SCANeR2 software package, provides a 150° field of view in a fully instrumented cockpit. Two different eco-driving assistance devices were added: a 7 inches display on the mid-console, and a force feedback system on the gas pedal. The feedback information was computed by comparing the car’s instant acceleration with an optimal acceleration level based on a proprietary consumption model of a Renault diesel engine. Basic eco-driving behaviors, like gear-shifting under 2000 Rpm, allows significant decrease of polluting emissions. Assisting drivers with visual, haptic, or visual-haptic on-board devices, in addition to low engine speed verbal instructions, lead to supplementary significant savings of polluting emissions. There is no significant difference between assistance feedback type; suggesting that haptic feedback provides the same ecoperformance as visual feedback. In particular, subjects show good adaptation to the haptic feedback pedal at first utilization of the system. They apparently relied more on haptic modality to achieve the eco-driving task, when they used both visual and haptic assistance. Résumé Dans cette expérimentation, 28 participants accomplissent une tâche de conduite dans le simulateur CARDS du Centre Technique de Simulation de Renault. Ce simulateur, équipé du logiciel de simulation SCANeR2, délivre un angle de vue de 150° dans un cockpit entièrement instrumenté. Deux interfaces d’assistance à l’éco-conduite complètent le dispositif expérimental : un écran de 7 pouces sur la console centrale et un dispositif appliquant un retour d’effort à la pédale d’accélérateur. Le retour d’information est calculé en comparant l’accélération instantanée du véhicule à un niveau d’accélération optimal, d’après un modèle de consommation de moteur diesel Renault. La pratique de l’écoProceedings of the Driving Simulation Conference Europe 2010 182 © Les collections de l’INRETS conduite, comme le changement de rapport sous les 2000 Rpm, permet de réduire significativement les émissions polluantes. L’assistance des conducteurs avec des systèmes d’aide visuel, haptique ou visuo-haptique, permet une réduction supplémentaire significative des émissions polluantes. Aucune différence significative n’a été constatée entre les différents modes d’assistance ; ce qui laisse penser que l’assistance haptique engendre la même écoperformance que l’assistance visuelle. En particulier, les sujets font preuve d’une adaptation satisfaisante à la pédale haptique lors d’une première utilisation du système. Ils accordent apparemment plus de confiance à la modalité haptique pour accomplir leur tâche d’éco-conduite en présence d’une assistance visuohaptique. Introduction Context Since the early seventies, the European Union has been controlling the polluting emissions of its vehicles by setting more and more drastic ecologic standards. From the early nineties, the development of the collective consciousness for ecology, associated to continuous fuel price increase urges countries to set up sustainable development plans for their vehicle market. In addition to the rules fixed to carmakers, actions have been led to sensitize car holders to eco-driving practicing. In particular, recently, eco-driving has been largely promoted by public organizations. Another way to provide help in ecodriving is to use an on-board assistance system with information on driving ecoefficiency. Feedback may be carried through various perceptive modalities: visual, auditory or haptic. Visual assistance feedback Nowadays, most of the cars are equipped with a digital information display of instant consumption. In order to enhance the visual salience of their consumption aid system, Honda has developed in 2009 a speedometer with changing colors, depending on drivers’ instantaneous eco-performance [Honda]. However, drivers’ visual attention is mainly focused on the road. By submitting driving participants to other visual on-board detection tasks, it is suggested that visual stimulus detection performance deteriorates, while reaction delay remains unaffected [Recarte & al, 2003]. Moreover, lane keeping and keeping distance to followed car, with the help of peripheral vision, appears to be impaired when watching a visual display on the speedometer, which is otherwise inefficient when the visual display is on the mid-console [Summala & al, 1998]. Haptic assistance feedback Haptic stimulation through gas pedal is another way to provide feedback information on eco-performance. Continental has developed an accelerator force feedback pedal AFFP [Continental], which vibrates to inform drivers on optimal Eco-driving performance assessment © Les collections de l’INRETS 183 gear-shifting time. Nissan proposes since 2009 an ECO Pedal [Nissan] to provide force feedback information on optimal pedal position, depending on engine state. Both announce fuel savings of between 5 and 10%. Haptic feedback pedal has already been studied in long-term and large field studies for speed limitation requirements. In this particular application, haptic appears to be more efficient than visual assistance. Significant decreases of mean and variation of speed, as well as polluting emissions are observed [Várhelyi & al, 2004]. Haptic feedback pedal acceptance is positively rated by drivers, but there is no willingness to pay for it [Adell & al, 2008]. In car following applications, haptic feedback pedal systems give information on inter-vehicular distance by modifying the gas pedal stiffness proportionally to the distance separating subject to forward car. This system allows significant decrease of standard deviation of inter-vehicle distance and braking reaction time [Kuge & al, 2005; Mulder & al, 2008].