Also represented in the network are gateways or cordon stations. Trips entering or exiting the county pass through these gateways much as cars cross the county boundaries. The amount and type of travel are dependent on the land use put into the model. Traffic analysis zones, or TAZ's, are the land use analysis units of the model. All the land use data is incorporated into zones which vary in size from a few city blocks in the urban area to several miles in the rural area.
Zones are combinations of either census blocks or block groups.
Zonal boundaries consist of the network and other natural or manmade dividers, such as canals and railroads, which limits the amount of crossings available for vehicles to use. The current Fresno County Model contains approximately 1,200 TAZ's. The land use is described in terms of type, intensity and location. This data is used in the trip generation process to estimate the number of trips that a household or employee will produce. The base year information is developed on a zone by zone average basis from census information and not on a house by house survey of who has zero autos versus who has two plus autos.