An automatic train protection system for detecting a position of a train at a trackside system on the basis of train control information including train position information, the automatic train protection system comprising: an onboard system configured to control the whole train and to communicate with the trackside system ; an onboard power supply device configured to supply power to the whole train and to generate a previous power shutdown signal providing an advance notice of shut-off of power supply to the onboard system; an onboard storage device configured to store position information of the train; an onboard speed measuring device configured to measure the speed of the train; and the trackside system ; wherein the automatic train protection system is configured such that: the train control information is stored on the storage device in response to occurrence of the previous power shutdown signal ; the train position information recorded on the storage device is transmitted to the trackside system when power supply to the onboard system is started; and the train control information stored on the storage device is deleted when a predetermined condition is satisfied; and wherein the predetermined condition is one of: while the train control information is stored on the storage device , the speed measuring device detects running of the train before the power supply is shut off; while the train control information is stored on the storage device , power supply to the train is resumed and the train control information is read from the storage device ; and while the train control information is stored on the storage device , power supply to the train is resumed and the stored train control information is read from the storage device and transmitted to the trackside system . an onboard system configured to control the whole train and to communicate with the trackside system ; an onboard power supply device configured to supply power to the whole train and to generate a previous power shutdown signal providing an advance notice of shut-off of power supply to the onboard system; an onboard storage device configured to store position information of the train; an onboard speed measuring device configured to measure the speed of the train; and the trackside system ; wherein the automatic train protection system is configured such that: the train control information is stored on the storage device in response to occurrence of the previous power shutdown signal ; the train position information recorded on the storage device is transmitted to the trackside system when power supply to the onboard system is started; and the train control information stored on the storage device is deleted when a predetermined condition is satisfied; and wherein the predetermined condition is one of: while the train control information is stored on the storage device , the speed measuring device detects running of the train before the power supply is shut off; while the train control information is stored on the storage device , power supply to the train is resumed and the train control information is read from the storage device ; and while the train control information is stored on the storage device , power supply to the train is resumed and the stored train control information is read from the storage device and transmitted to the trackside system . while the train control information is stored on the storage device , the speed measuring device detects running of the train before the power supply is shut off; while the train control information is stored on the storage device , power supply to the train is resumed and the train control information is read from the storage device ; and while the train control information is stored on the storage device , power supply to the train is resumed and the stored train control information is read from the storage device and transmitted to the trackside system . <EOS>