This study documents a new demand modeling approach for scarce truck parking facilities. In recent years the parking sites and service areas on Germany's federal highway system have been frequently overcrowded by heavy goods vehicles. Especially at night, the shortage of parking space is evident; the shortage counteracts the goals of the Europe-wide hours-of-service (HOS) rules for truck drivers. The simulation-based examination aims to close the gap between empirical data and the decision support needs for target-oriented improvements. First a generic approach was developed reconstructing demand for truck parking space at an arbitrary segment of highway. The unique features are the time resolution and the explicit functional dependency on the HOS regulation. A prototype of this model having been applied to one study area in Germany, possible adaption to the United States is discussed. In summary the methodological contribution seeks to establish the basis of a test of various transport policy measures and subsequent performance reviews.