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Saturation Traffic Counts Performed

Each year TxDOT TPP's Traffic Section (TPP-T) collects (through contractors) thousands of traffic counts on numerous road segments in four to six urbanized areas. These “saturation” counts are 24-hour tube counts performed on both on and off-system roadways. The counts are collected on Mondays through Thursdays (excluding holidays) and are used to obtain data to support the travel model validation process and for the Highway Performance Monitoring System (HPMS) database. These counts are in addition to annual counts performed on state highways.

Saturation counts are average daily traffic (ADT) counts meaning that they are merely total axles divided by two. Annual TxDOT counts are annual average daily traffic (AADT) counts that are adjusted for seasonal and monthly variations.

Model validation is the process whereby the model's credibility is proven based on replicating observed conditions (e.g. traffic counts, vehicle miles of travel). The MPO model's validity will be determined by comparing modeled traffic volumes to actual counts (i.e. the saturation counts) on each facility comprising the network.