The Arnold rapido model railroad product line was similar in many ways to other model railroad lines from Europe. There are fundamental differences between model railroaders in Germany and in North America.  While the Americans like to view themselves as the heroic locomotive engineer, the Germans view themselves as a signal tower operator, with numerous trains under their direct control.  This difference shows up in many different ways, but one major difference is that German model railroaders have extensive signal systems which are used to control multiple trains.

     No proper German model railroad would go without a signal system. To meet this need, most German lines of model trains include operating relays and track devices to facilitate such control. The rapido brand was no exception.

     In addition to the automatic operation features, Arnold rapido made a significant contribution to the model railroad hobby, the Rapido Coupler.