Vehicle allocation system includes an information provision apparatus, a first apparatus: control apparatus, and a user's second apparatus: user terminal apparatus. Processor of the information provision apparatus calculates a first driving plan for a vehicle in response to request information. When a second driving plan different from the first driving plan is calculated based on detection information acquired from the vehicle, the processor determines the cause of a change in the driving plan on the basis of the detection information. The processor transmits cause information including the cause to the user terminal apparatus. The user terminal apparatus presents the cause information on a display.