This paper discusses a way to detect the driver’s intention to decelerate in a car-following situation. A field observation and an experiment were conducted. In the field observation, the data were collected for analyzing a driver’s maneuvering of the accelerator and brake pedals in order to design a system that can detect the driver’s intention to decelerate. The method based on the covering brake pedal found to be highly reliable. An experiment was conducted to evaluate the influence of the proposed system. The results showed that the system was effective in improving the accelerator release time and brake onset time.