Apparatus and method for detecting decrease in air-pressure for use in two-wheeled vehicle, and program for judging decompression for use in two-wheeled vehicle

An apparatus for detecting decrease in air-pressure for use in a two-wheeled vehicle including: a wheel speed detecting means for detecting wheel speeds; an acceleration calculating means for obtaining accelerations of a vehicle body of the two-wheeled vehicle; a slip rate calculating means for calculating slip rates when the acceleration of the vehicle body is in a specified range which is proximate to zero; an average value calculating means for obtaining average values of the slip rates and average vehicle body speeds; a difference calculating means for obtaining differences between the average values of the slip rates and a reference value which is based on an average vehicle body speed as preliminarily set when an internal pressure is normal; and a means for judging decrease in internal pressure. A decrease in air-pressure in a two-wheeled vehicle can be judged so as to enable safe driving.