Travel demand modeling is the brainchild of civil engineers and was developed to facilitate improved transportation planning. Although you can use four different approaches in travel demand modeling — trip-based, integrated trip-based, tour-based, and activity schedule-based — the trip-based approach is most relevant to crime analysis.
The trip-based approach is broken into the following four steps:
- Trip generation. Model the trip production (the quantity of crime trips that originate in a zone of origination — a spatial region, like a neighborhood or subdivision) and the trip attractions (the quantity of crime trips that end in the zone of destination — the spatial region where the criminal act is executed).
- Trip distribution. Incorporate a trip matrix — a matrix of rows and columns that covers a study area and depicts the patterns of trips across it— and a gravity model — a model that describes and predicts the locational flow of objects across space — to quantify the count of crime trips that occur between each zone of origination and each zone of destination.
- Modal split. A modal split is the portion of travelers that uses particular trip paths across a study area. For travel demand modeling, you'd generate a count of the number of trips for each zone-of-origination/zone-of-destination pair that occurs via each available route. The choice between routes can be modeled statistical or mathematical.
- Network assignment. Assign probability and predict the most likely routes that a criminal would take when traveling from a particular zone of origination to a particular zone of destination across the network of potential travel paths.