A skim is a measurement taken from the traffic model. Typical examples are the mean travel time from a zone A to a zone B, which is calculated from the travel times of all paths found, as well as the total PuT journey time, which is the sum of the journey times of all PuT passengers. Skims can be divided into global skims, which describe properties of the entire traffic model, and into skims gained per OD pair. The latter are stored in skim matrices, whereby the entry xij for the skim value, refers to the relation from zone i to zone j.
Generally, skims measure the properties of the traffic model. In feed back models they are also the input data for the demand modeling procedures, especially for trip distribution and mode choice.
