Key numbers are listed on the back of driving licences in credit card format. They indicate additional information, conditions and restrictions of the driving licence.
The key number 174 gives road users an additional permit that younger drivers no longer have today. A three-digit key number is only valid within Germany, while two-digit numbers are valid throughout the EU. The ADAC has listed a large number of the key figures and their meanings on its homepage.. Many are unaware of the importance of key figures. The number 174 plays a major role, especially for older road users.