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question, he adds, for example by providing information about the options for opening the charging flap and about the charging procedure in general. People have a limited amount of attention to give to any task, so it is essential to ensure that a UI presents the information the driver needs and wants at the right time, without it being distracting. While avoiding driver distraction is not specific to EVs, it always plays a major role in the development of the interface, the HMI expert notes, emphasising the importance of what he calls holistic HMI. That means the system recognises the user’s condition, knows the current driving situation and adjusts the information output in terms of both content and modes accordingly. “For this purpose, information is collected and presented quickly, in a focused and clear manner,” he says. “The flow of information is reduced, considering the driving situation and the driver’s condition. Only the information and options for action that are relevant in the current situation are offered.” A holistic HMI also provides the driver with reliable feedback that they initiate, which builds confidence in the vehicle’s functions. In this context, he adds, it is also important that the information is reduced as much as possible and adapted to the situation. Depending on the driver’s condition, the system should for example decide whether to switch on assistance systems. Distraction, bad and good The HMI development platform provider also values such minimalist approaches, enriched with additional information when it is needed. “Basically, when something important happens, the UI needs to distract you and must ask for your attention,” he says. Because keeping the driver’s attention on the road is so important, it is vital to be able to measure the distraction that any particular aspect of the UI might cause. The most important sensors for doing so are in-cabin monitoring devices such as cameras. “As a result, gaze and head movements as well as body position are analysed to determine the driver’s attentiveness,” the provider says. “Indirect measurement is also possible, for example via the duration and frequency of touchscreen operation.” When the target of ‘distraction’ is a passenger in a taxi or an autonomous vehicle, the focus is on how to advertise goods and services to them without causing annoyance. The HMI development platform provider says his company is using a manual process to measure test subjects’ reactions. “Let’s say you arrive somewhere in an autonomous taxi; it could make offers of services at that location, such as a visit to a theatre. “If you have just arrived from the airport and you get these questions you might be irritated and probably won’t accept any such offers, but if you are driving by that location and the car tells you, ‘If you look to the right you will see our famous theatre and I can book tickets for tomorrow,’ you are more likely to accept that offer.” The company is thinking through what might be expected from cars in the future and how user interfaces can best provide prompts, and trying to figure out how to present the information and how often. An advert could, for example, be shown full- screen and overwhelm the person because you want to push that offer, or it could just present a small indicator that the user can select to get more details. “You probably don’t want to be annoyed by being shown new information every 2 minutes, and one or two adverts during the journey are probably enough, although perhaps you are fine with constantly receiving new offers,” the provider says. “These are the things we are trying to measure and figure out.” Ergonomics and measurement All of the above issues are problems addressed by ergonomics, the science that studies the interactions between humans and all kinds of engineered systems. As well as addressing physical aspects such as the comfort of seats and how easy (or otherwise) controls are to operate, it also encompasses mental workload under the discipline of cognitive ergonomics. With the ubiquity of screens in vehicles and the multiplicity of ways of interacting with them using bezel buttons, track balls, touchscreens and so on, engineers need ways to measure their effectiveness. One of the tools available for this is Fitts’ Law, which is used to model the act of pointing, either by physically touching something with a hand or finger or pointing to an object on a screen using a pointing device. Formulated by American Focus | User interfaces In modern user interface designs, almost the whole of the dash area is used to allow the driver and front seat passenger to interact with the car’s systems (Courtesy of Elektrobit) 66 Autumn 2022 | E-Mobility Engineering