Yasuo Sakaguchi

Modeling of Driving Behavior When Approaching an Intersection Based on Measured Behavioral Data on An Actual Road

It is important to develop a driving assistance system that conforms to individual driving behavior. An individuals usual driving behavior is generally adapted to road and traffic situation; therefore, we propose that assistance be provided when that behavior deviates from normal. We developed specially equipped vehicles to collect natural behavioral data from repeated driving experiments on an actual road. We subsequently developed a Bayesian network model of occurrence of behavioral events from the data obtained when approaching a specific intersection with a stop sign. Any deviation from usual operation behavior can be estimated using this model. Unusual behavior can be regarded as inappropriate behavior and therefore its detection can be applied to driving assistance methods, such as warning presentation.

Simulating the human vision of elderly for designing control panels

We propose an approach to designing control panels for the elderly based on a computational model of human visual properties, adaptation to light, spatial sensitivity and spectral sensitivity of eyes. The model is implemented as a filter to simulate a human visual system using image processing techniques. The paper describes the proposed method and shows evaluation results. The system allows the designer to predict the difficulties for the elderly to read the visual information under various illumination environments, and we apply our visual model to the prototype evaluation of control panels of the consumer product, including shower-toilets with illuminated buttons.

Displaying method for on-board displays adaptive to luminance of the driving environment

Recently, number of on-board visual display, such as a navigation system is increasing. A driver gazes such display in short period of time in driving. Thus, it is important to improve visibility of the on-board display. We propose two methods about visibility improvement of on-board display. First, we mention about simulating method of creation of the perceived brightness distribution of a scene which is useful for design of the high visibility on-board display. Second, we describe displaying method for the on-board display to control luminance and chromatic saturation of displaying image. Both methods are based on the adaptation property of human vision. Experimental results of subjective and objective evaluation that compare the conventional display and our new one indicate the effectiveness of the second method.

Displaying method adapted to visual acuity and brightness under viewing environment

The given time to gaze at an on-board display is very short from the viewpoint of safe driving. Therefore, the visibility of the on-board display should be more excellent than the general display. This report describes a method for improving display visibility. In this method, character size is decided, based on the spatial frequency properties, and the brightness of the display screen is selected using the adaptation properties. In the decision of character size, the two-dimensional frequency of the character (linear density) is calculated. Next, appropriate character size is determined from correspondence of this frequency and the spatial frequency (visual acuity). In a car-navigation display under low illuminance at night-time, the background luminance of the display screen is decided by the adaptation properties. Besides that, the character luminance is determined by the appropriate contrast with the background. Some experiments have shown that these methods were very effective in improving the display visibility.

Visibility Evaluation of Vehicle Display and Its Application.

In recent years, as vehicle technology has advanced, the use of on-board display devices has increased. In particular, vehicles with navigation systems are rapidly increasing in use. With such systems, when a driver operates a vehicle, the driver detects and judges road situations while looking at the route-guided map on the navigation system display. Thus, from the safety point of view, improvement of visibility of the navigation system is very important. We have developed a noncontact gaze duration measurement system for on-board navigation systems. The system uses a TV camera on the dashboard to detect the drivers eye movements that are illuminated by infrared rays. In addition, the usefulness of the navigation system with voice route guidance compared with a conventional nonvoice system is demonstrated using measurements based on this method in the daytime and at night time. It is clear that the voice guidance is effective in decreasing gaze duration.