a display recommendation speed is determined out of the first recommendation speed and the second recommendation speed at s 103 if the first and second recommendation speeds are set the lower one of the recommendation speeds is displayed as the display recommendation speed if only one of the first and second recommendation is provided the only one recommendation speed is displayed as the display recommendation speed if none of the first and second recommendation speed is provided a preset speed such as the legal speed limit is displayed as the display recommendation speed thereafter information about reasons of the display recommendation speed is formed at s 104 and displayed at s 105 if for example a display recommendation speed is displayed based on a traffic jam a blue colored message u201c traffic jam ahead u201d is formed to be displayed by the display unit 22 with a blue colored display of the display recommendation speed the first recommendation speed as shown in fig2 d if the esc fails a red colored message u201c esc fails u201d is formed to be displayed with a red colored display of the display recommendation speed the second recommendation speed as shown in fig2 a the red colored message and red colored display recommendation speed represents higher importance than the blue colored message and display recommendation speed at s 105 the display recommendation speed that is determined at s 103 the information about reasons of the display recommendation speed and the control speed that is set at s 302 or s 305 are outputted to the display unit 22 in which the display recommendation speed is displayed by a red or blue spot light and the control speed is.