Driving assistance device

A driving assistance device of a vehicle comprising a propulsion device, a brake device, and a steering device, the driving assistance device comprising:

• a temperature measuring device configured to measure an outside temperature;
• a plurality of external environment sensors configured to detect an object around the vehicle;
• a controller configured to receive a signal from the temperature measuring device and a signal from each of the external environment sensors, and control at least one of the propulsion device, the brake device, and the steering device to assist a user in driving the vehicle;
• and
• a notification device configured to notify the user of information based on control by the controller, wherein
• when the controller does not receive the signal from at least one of the external environment sensors and determines that the outside temperature measured by the temperature measuring device is equal to or higher than a prescribed value, the controller is configured to determine that the at least one of the external environment sensors has failed and cause the notification device to notify information regarding a failure of the driving assistance device, and
• when the controller does not receive the signal from at least one of the external environment sensors and determines that the outside temperature measured by the temperature measuring device is lower than the prescribed value, the controller is configured to determine that the at least one of the external environment sensors is inoperative due to a low temperature and cause the notification device to notify information indicating that the driving assistance device is in a degraded performance state.