A longitudinal driver assistance system in a motor vehicle includes a capture system configured to detect upcoming relevant events which require adaptation of a predefined maximum permissible top speed, and a functional unit which, upon detecting an upcoming relevant event, is configured to determine, based on a location of the upcoming relevant event, a first location or first time, the reaching of which causes the functional unit to output a notification to a driver of the vehicle relating to an automatic adaptation of the maximum permissible top speed. The functional unit is also configured to determine a second location or time to be reached after the first location or first time, respectively, the reaching of which causes the functional unit to intervene in a longitudinal guidance of the motor vehicle in a direction of a new maximum permissible top speed at the location of the upcoming relevant event if there is no driver-initiated refusal of the automatic adaptation of the maximum permissible top speed. Upon detecting the upcoming relevant event, the functional unit is configured to determine a third location or third time to be reached after the second location or second time, respectively, up to which point a driver-initiated refusal of the automatic adaptation of the maximum permissible top speed is permitted.