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A Distance Control Assist System (DCA) aiming at facilitating the driver maintaining a following distance to a lead vehicle in congested traffic was developed. The DCA imposes active force to the driver’s foot to urge him or her to release the accelerator pedal as well as decelerates automatically when the host vehicle comes too close to a lead vehicle. This paper introduces the system description and a field test conducted to evaluate effectiveness of the DCA. As a result of the field test, comparison of the driver performances between with and without the DCA showed that numbers of braking by the drivers were decreased, and comparison of NASA-TLX scores showed subjective workload was reduced by the DCA. These results suggested that the DCA can contribute to mitigation of the driver’s workload while following situations.

A study was made on a control method for an adaptive cruise control (ACC) system that uses vehicle-to-vehicle communication to achieve a substantial improvement in string stability and natural headway distance response characteristics at lower levels of longitudinal G. A control system using model predictive control was constructed to achieve this desired ACC vehicle behavior. Control simulations were performed using experimental data obtained in vehicle-following driving tests conducted on a proving ground course using a platoon of three manually driven vehicles. The results showed that the proposed ACC system satisfactorily achieved higher levels of required ACC performance.

An investigation was made of the relationship between the driving speed at the time of impact and the injury levels suffered in accidents. The results showed that a 5 km/h or more reduction in collision speed tends to mitigate injury severity. Using sensors and brake actuators already in practical use, we have started to research a braking system aimed at reducing the collision speed by at least 5 km/h in rear-end collisions. The system estimates the risk of a collision with the vehicle ahead. If it judges there is a very high possibility of a collision, it applies the brakes.

This paper describes a headway distance control system for platoon driving on an automated highway system (AHS). The system implemented on a test vehicle is described first, followed by a description of a vehicle control method based on the use of throttle and brake actuators. This method makes it possible to obtain the target acceleration and deceleration regardless of the vehicle speed range and the rate of acceleration or deceleration. Experimental and simulation results obtained with this method are presented. A control method is then described that uses inter-vehicle communication and laser radar to maintain a constant headway between vehicles. The results of simulations and driving tests conducted with three vehicles are presented to illustrate that the use of inter-vehicle communication is highly effective in improving headway control performance.