Keywords

1 Introduction

1.1 Background

In recent years, the center of the development of the world’s automobile industry is shifting towards new energy vehicles, and under the guidance of government policies of various countries, the new energy vehicle industry has already had a relatively large scale and market. With the advancement of technology, people continue to bring the experience of using other intelligent products into the use of cars, and the requirements for the interactive experience of cars are getting higher and higher. At the same time, with the rapid development of the economy, user needs are gradually changing from material needs to spiritual needs, and products are also changing from functional and appearance designs to experience designs to meet user needs [1]. As a personal means of transportation, a car meets the basic functions of people’s travel requirements. The human-computer interface in the car, as the display carrier of the car’s functions, is the most intimate part of the driver [2], and its quality will directly affect the driving experience. With the continuous changes in the form of interaction in the car, from the traditional instrument panel to the current HUD, etc., it is still unclear which form of interaction is more likely to win the favor of users.

1.2 Dashboard and HUD

As one of the important elements of the car interior, a dashboard is an important tool for car information transmission. It always reflects the state of the car and guides the driver’s driving operation. It is the state display part of the car and the interface of human-computer interaction [3]. However, starting from the simple instruments in the 1950s, the driver’s visual information output is almost completely concentrated on the traditional instrument panel; The function is gradually enhanced to an interactive multi-functional information panel. At the same time, additional visual and cognitive pressure problems will be generated, and its complexity becomes the main problem [4, 5]. The dashboard will also directly have adverse effects, line of sight and frequent observation for a long time will lead to cognitive distraction [1]; in response to such problems, the head-up display device HUD came into being, and its application in automobiles has been proven to have many advantages, such as the driver’s ability to control the driving speed hold is better, pay more attention to road traffic, don’t have to move the camera to the car dashboard, etc. [6]. Based on NHTSA’s conclusions from previous studies [7], HUDs may also be used to provide drivers with critical information while minimizing the time the driver takes their eyes off the lane ahead of the driver, which can improve driving by reducing driver eye movement and visual tracking. The speed at which employees acquire information and the time to focus. But at the same time, the design of the HUD will directly affect the driving, which may cause the driver’s separation and narrow vision channel, and some studies have shown that the accuracy of information is reduced when augmented reality (AR) is implemented on the HUD. In the application of AR-HUD designers should consider the display timing of information and the optimal design of HUD, etc. [8].

1.3 Graphics Design

Graphics play an important role in modern interfaces and therefore recent empirical research has focused on enhancing graphics processing. The 2D (flat) vs. 3D (three-dimensional) design debate is inconclusive in automotive HMI design, partly due to a lack of empirical evidence to support one or the other graphic style from a functional and aesthetic standpoint. You F et al. compared the three colors of red, green, and blue under the HMI, as well as the five levels of daytime and nighttime contrast, to make the color design of the vehicle center console a reference; Pfannmller L et al. proposed information display timing and The optimal design of the HUD has a significant impact on the driving experience; Ng, A.W.Y., et al. proposed that the visual complexity is related to the number of visual elements displayed in detail in the graphics, thus requiring more attention and time from the user to recognize [9]. So, the vehicle HMI’s design case should be measured and considered from multiple perspectives such as the number of visual elements, graphic colors, and presentation forms.

In this study, the HMI experiment plan is divided into two groups of 2D and 3D, Dashboard and HUD for comparison, to explore the user preferences of the Dashboard and HUD display methods under 2D and 3D, and to explore the visual experience through questionnaires and in-depth interviews The user preference scheme under the dimension, and the design strategy is given to provide a practical reference for the information display design in the driving state.

2 Experiment

Since more than 80% of the driver’s information comes from visual information when driving [10], and visual reminders are more timely and effective than auditory reminders in emergencies, maximizing visual resources is conducive to allowing drivers to focus on Safe Driving. The experiment compares the user’s preferences for the four schemes of 2D-Dashboard, 3D-Dashboard, 2D-HUD, and 3D-HUD by making statistics on the information elements in the driving process and redesigning them, and tries to give design strategies and conclusions.

2.1 Comparative Research Method

The comparative research method is a method of researching and judging the degree of difference between objects. In this experiment, two groups of comparison samples, namely 2D-Dashboard and 2D-HUD; 2D-Dashboard, and 3D-Dashboard are used to compare user preferences, to find out which method is easier to obtain user preferences.

2.2 Statistics of New Energy Vehicle Instrument Display Elements

In the preparatory stage of this experiment, ten new energy vehicles were randomly selected, and the information displayed on the instruments during their normal driving was counted. The information displayed was speed, navigation, and road condition information, cruising range (battery), lights or seat belts and other reminders, and auxiliary information such as time and temperature, total mileage, and media (see Table 1). Since the information that changes during the driving process is mainly focused on speed, navigation, and vehicle battery, the display methods of the three types of information were redesigned during the experimental preparation stage. The styles are flat and three-dimensional, and the carriers are dashboard and HUD respectively. Four ways to display information. Reminders and auxiliary information appear in the design plan as the background, and non-essential total mileage and media do not appear in the plan as design objects.

Table 1. Display element statistics
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2.3 Case Design

In the scheme design, to simulate the realism of information display in the driving scene, the dashboard of any model in the market was randomly selected as the background to simulate the dashboard information, and the blurred traffic background was randomly selected to simulate the HUD display background. 2D (referring to the flat effect) mainly uses lines to form information, and 3D (referring to the three-dimensional effect) uses real road condition information, speed mirror processing, and navigation light effects to increase the three-dimensional sense. The final four design schemes are shown in Table 2.

Case 1: 2D-Dashboard. The left side of the 2D-Dashboard is the speed and battery life information, and the right side is the navigation information. Below the speed information, the power battery life is displayed in the form of horizontal lines, surrounded by lights, gears, seat belts, speed limits, time, and temperature information; the navigation on the right is mainly based on the information of the three lanes overlooking and other vehicle information, supplemented up and down Take lane selection and navigation information.

Table 2. The 4 case designs
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Case 2: 3D-dashboard. The 3D-Dashboard also uses speed and battery life information on the left, and navigation information on the right. The difference from the 2D-Dashboard is that the speed and battery life information uses light effects and mirror effects to increase the three-dimensional effect, and the navigation information on the right corresponds to the physical lane and road conditions, which are more realistic and three-dimensional.

Case 3: 2D-HUD. The information presented on the HUD is more concise. Other information in the background is removed, and only the speed information, battery life information, navigation and road condition information are retained. In addition, only the upper right corner of the speed is added. Speed limit value. The visual effects of speed information, battery life information, navigation and traffic information are the same as the 2D-Dashboard.

Case 4: 3D-HUD. It is the same as 2D-HUD, only the speed, battery life, and navigation information are kept, and only the speed limit value is added in the upper right corner of the speed, and the visual effect of the three information is the same as that of the 3D-dashboard.

2.4 Questionnaires Design

In the preparatory stage of the experiment, to explore the user’s preference for visual display differences between 2D and 3D; Dashboard and HUD, and which of the four cases is the user’s most preferred visual presentation scheme, the questionnaire was edited and set according to the preferences of the four schemes. After removing the basic information of the user, the questionnaire includes four multiple-choice questions:

  1. 1.

    For the cases 2D-dashboard and 3D-dashboard, which one do you prefer?

  2. 2.

    For the cases 2D-dashboard and 2D-HUD, which one do you prefer?

  3. 3.

    Among the four cases, which one do you prefer?

  4. 4.

    Which design element do you like in this (answer to question 3)?

The questionnaire was set up for four questions, and the user’s personal information was added for statistics, including the user’s gender, age, and driving age. The questionnaire is produced by the third-party questionnaire platform Questionnaire Star and published on the network platform.

2.5 Experimental Hypothesis

  • Hypothesis 1: For designs in 2D and 3D dimensions, users prefer 3D designs.

  • Hypothesis 2: For the display forms of the Dashboard and HUD, users prefer the display form of the HUD.

  • Hypothesis 3: The user’s most preferred case is the 3D-HUD solution, which is related to the user’s driving experience.

  • Hypothesis 4: In daily driving, users will prefer and pay attention to navigation and traffic information, and speed information.

3 Experiment

3.1 Participants

In the experiment, 130 participants were randomly invited to answer the questionnaire, and 130 valid questionnaires were recovered. Among them, the male-to-female ratio of the participants is 60:56, the age span is 18–45 years old, and the actual driving experience spans from 0 to 50,000 km.

3.2 Experiment Implementation Process

To more comprehensively obtain the participants’ preference for the instrument display scheme, the experiment randomly invited 130 participants to participate in the questionnaire survey. Download the questionnaire data on the platform to get the original data form. Before answering, the participants were informed that the content of the questionnaire would involve personal information such as age and driving mileage, and the information was collected with the written permission of the participants, allowing the information to be used for academic investigation in this study.

The experiment recovered 116 valid samples, among which those whose answering time was less than 30 s were considered invalid samples, the sample collection time lasted 72 h, and the returned questionnaire data was stored in the form of excel.

4 Results

4.1 Result 1

For question 1: “Which one do you prefer, 2D-dashboard or 3D-Dashboard?”, 100 people chose the 2D-dashboard and 16 people chose the 3D-Dashboard (see Table 3).

Result 1 shows that among 2D and 3D design styles, 86% of users will prefer the 2D design style. When the screen uses two-dimensional graphics, that is, lines and geometric figures to indicate specific road conditions and other information, users will prefer; Analyzing experimental result 1, it is concluded that compared with 2D and 3D, the 2D dashboard design is more likely to be liked by people, which is contrary to hypothesis 1, indicating that in the subsequent design, the 2D design can be used to win users love and attention.

Table 3. Preference between 2D-dashboard and 3D-Dashboard
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4.2 Result 2

For question 2: “For case 2D-Dashboard and case 3D-HUD, which one is your preference?”, 86 people chose 2D-Dashboard, 30 people chose 2D-HUD, and the proportions were 74% and 26% (Table 4).

Table 4. Preference between 2D-dashboard and 2D-HUD
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Result 2 shows that among the design styles of Dashboard and HUD, 74% of users prefer the Dashboard design style. When the information content is the same, the presentation form based on Dashboard will be more likely to be liked by users. Analyzing experimental result 2, it is concluded that compared with the HUD, the presentation form of the Dashboard is more likely to be liked by people, which is contrary to hypothesis 2, but the specific reason for the preference is not clear.

4.3 Result 3

Table 5. Preference between 2D-dashboard, 3D-dashboard, 2D- HUD and case 3D-HUD
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For question 3: “For case 2D-dashboard, 3D-dashboard, 2D-HUD and case 3D-HUD, which one is your preference?”, 45 people chose 2D-dashboard, 39 people chose 3D-dashboard, 24 people chose 2D-HUD, 8 people chose 3D-HUD, the proportions were 38.8%, 33.6%, 20.7%, 6.9% (Table 5).

After obtaining the questionnaire data, 20 people were randomly selected for interviews and asked what the specific reasons were when the users chose their most preferred solution. The statistical table obtained is shown in Table 6, which can be summarized into five types of reasons, namely simple, clear, good-looking, harmonious, and relatively easy to find information, among which more people choose the reason because of simplicity and clarity, which can show to a certain extent that when the design is simple and clear, it may be easier to be loved by users.

Table 6. Preference between 2D-dashboard and 3D-Dashboard
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4.4 Result 4

For question 4: “Which design element do you like in this product (the answer to question 3)?”, 89 people mentioned navigation information, 87 people mentioned speed, and 4 people mentioned battery life display. No one mentioned other information such as time, lighting, etc. (see Table 6).

Table 7. Reasons about why people like the case
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According to the selected ratio, navigation and road condition information, and speed information are the two elements that users pay the most attention to. The difference between the selection ratio is only 1.7%, which is negligible, and the number of people who choose these two elements is much higher than battery life information and other information, which are negligible. This is in line with Hypothesis 4 of this paper, indicating that users pay more attention to navigation and road condition information, as well as speed information in actual driving. Therefore, in the HMI design of the car, more design research can be done on navigation and road condition information, as well as speed information (Table 7).

5 Discussion

Through statistics on the preferences of the dashboard and HUD display information of 130 users, we concluded that among the 2D and 3D design styles, users prefer the 2D design style; among the presentation methods of dashboard and HUD, users prefer the presentation form of the Dashboard; among the four preferences, the 2D-dashboard design is the most preferred style by users, which is consistent with the selection trend of the aforementioned users. When discussing the reasons for preference with users, users indicated that the most favorite design is a simple and clear design, which indicates that in the subsequent HMI design, we should focus on using simple elements, such as simple geometry in 2D, and avoid using overly complex designs element. In addition, in the comparison between HUD and Dashboard, the user prefers the Dashboard form. It is speculated that this may be related to the user’s driving experience, but this has not been verified by the data.